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MJPEG tools(MJPEG Linux Square) MJPEG tools(MJPEG Linux Square)
MJPEG HOWTO - An introduction to the MJPEG-toolsPraschinger Bern-
hardv1.49MJPEG capture/editting/replay and MPEG encoding toolset
description
Introduction
I wrote this things down, because I had many sheets with notes on them.
This should be some kind of summary of collected knowledge of this
sheets. Andrew Stevens helped with encoding and VCD knowledge and
hints.
The mjpegtools are a set of programs that can do recording, playback,
editing and eventual MPEG compression of audio and video under Linux.
Although primarily intended for use with capture / playback boards
based on the Zoran ZR36067 MJPEG codec chip, the mjpegtools can easily
be used to process and compress MJPEG video streams captured using
xawtv using simple frame-buffer devices.
The HOWTO for the tools intended to give an an introduction to the
MJPEG-tools and the creation of MPEG 1/2 videos. VCD and SVCD, and the
transcoding of existing mpeg streams.
For more information about the programs read the corresponding man-
page.
Achtung es gibt auch eine deutsche Version bei:
There is also a manpage of this text, you can read it with ”man mjpeg-
tools” if installed.
The text version of this text is available via cvs, you should get it
with a tarball or the precompiled package (RPM and deb).
In the following picture you see the typical workflow when you record a
video. Cut it afterwards and encode it. In the picture you also see
the connections to other programs. These parts are in grey, the parts
in blue can be done with the mjpegtools.
Video encoding workflow
Unsorted list of useful Hints
You have to compile and install the mjpeg_play package, for this read
the README & REQUIRED_SOFTWARE & INSTALL. If you do not want to
compile it, you can download the mjpeg .RPM or .DEB package at Source-
forge.
There is a script in the scripts/ directory. This script is something
that show's you a way how it can be done. It also creates (under cer-
tain circumstances) videos that look quite good. Better videos you only
get by tuning the parameters yourself.
You will usually have to load the drivers for the Buz or DC10 or LML33
cards.So you have to run the update script providing as option the name
of your card you have. The script is usually in /usr/src/driver-zoran/.
The zoran kernel driver below the kernel 2.4.4 do not work. You have
to use the driver available from:
The driver for the Matrox Marvel card also works, more information
about it:
If you compile the tools on a P6 based computer (PPro, P-II, P-III,
P-4, Athlon,Duron) then never try to let them run on a P5 based com-
puter (Pentium, Pentium-MMX, K6, K6-x, Cyrix, Via, Winchip). You'll get
a ”illegal instruction” and the program won't work.
If lav2yuv dumps core then one possible cause is no dv support was
included. To enable it make sure that libdv is installed on the system.
This will be necessary if you are using a digital camera (or analog to
DV converter such as the Canopus ADVC100) and converting the dv avi
format into the MPEG format.
Start xawtv to see if you get an picture. If you want to use HW-play-
back of the recorded streams you have to start xawtv (any TV applica-
tion works) once to get the streams played back. You should also check
the settings of your mixer in the sound card.
If you compile the tools on a platform other than Linux not all tools
will work. Mjpegtools on a OS/X system for example will not have V4L
(video4linux) capability.
Never try to stop or start the TV application when lavrec runs. If you
start or stop the TV application lavrec will stop recording, or your
computer could get ”frozen”. This is a problem of v4l (video4linux).
This problem is solved with v4l2. If you use v4l2 you can record the
video and stop and start the tv application whenever you want. But
v4l2 is currently (7. Jan. 2003) only supported for the zoran based
cards (BUZ, DC10, DC10+, LML33) if you use the CVS driver from
mjpeg.sf.net tagged with ZORAN_VIDEODEV_2. And this driver only works
with the 2.4.20 kernel and the 2.5.* development kernel.
One last thing about the data you get before we start:
Audio: ( Samplerate * Channels * Bitsize ) / (8 * 1024)
CD Quality:(44100 Samples/sec * 2 Chanels * 16 Bit) / (8 * 1024)=172,2 kB/sec
The 8 * 1024 convert the value from bit/sec to kByte/sec
Video: (width * height * framerate * quality ) / (200 * 1024)
PAL HALF Size : (352 * 288 * 25 * 80) / (200 * 1024) = 990 kB/sec
PAL FULL size : (720 * 576 * 25 * 80) / (200 * 1024) = 4050 kB/sec
NTSC HALF size: (352 * 240 * 30 * 80) / (200 * 1024) = 990 kB/sec
NTSC FULL size: (720 * 480 * 30 * 80) / (200 * 1024) = 4050 kB/sec
The 1024 converts the Bytes to kBytes. Not every card can record the
size mentioned. The Buz and Marvel G400 for example can only record a
size of 720x576 when using -d 1, the DC10 records a size of 384x288
when using -d 2.
When you add audio and video datarate this is what your hard disk has
to be able to write constantly streaming, else you will have lost
frames.
If you want to play with the --mjpeg-buffer-size. Remember the value
should be at least big enough that one frame fits in it. The size of
one frame is: (width * height * quality ) / (200 * 1024) = kB If the
buffer is too small the rate calculation doesn't match any more and
buffer overflows can happen. The maximum value is 512kB.
How video works and the difference between the video types is explained
here:
There you also find how to create MPEG Still Images for VCD/SVCD.
A good description of DV (Digital Video) can be found here:
Some books we found usefull
written in English:
Digital Video and HDTV by Charles Poyton (ISBN 1-55860-792-7)
Digital Video Compression by Peter Symes (ISBN 0-07-142487-3)
Video Demystified by Keith Jack (ISBN 1-878707-56-6)
written in German:
Fernsehtechnik von Rudolf Maeusl (ISBN 3-7785-2374-0)
Professionelle Videotechnik - analoge und digitale Grundlagen von U.
Schmidt (ISBN 3-540-43974-9)
Digitale Film- und Videotechnik von U. Schmidt (ISBN 3-446-21827-0)
If you know some other really good book about that, write us!
Recording videos
lavrec examples
Recording with lavrec look's like this:
> lavrec -f a -i P -d 2 record.avi
Should start recording now,
-f a
use AVI as output format,
-i P
use as input source the SVHS-In with PAL format,
-d 2
the size of the pictures are half size (352x288)
record.avi
name of the created file.
Recording is finished by pressing Crtl-C (nowadays: Strg-C). Sometimes
using -f A instead of -f a might be necessary
Other example:
> lavrec -f q -i n -d 1 -q 80 -s -l 80 -R l -U record.avi
Should start recording now,
-f q
use Quicktime as output format,
-i n
use Composite-In with NTSC format,
-d 1
record pictures with full size (640x480)
-q 80
set the quality to 80% of the captured image
-s
use stereo mode (default mono)
-l 80
set the recording level to 80% of the max during recording
-R l
set the recording source to Line-In
-U
With this lavrec uses the read instead of mmap for recording this is
needed if your sound card does not support the mmap for recording.
Setting the mixer does not work with every sound card. If you record
with 2 different settings and both recordings are equally loud you
should setup the mixer with a mixer program. After that you should use
the -l -1 option when you record using lavrec
The size of the image depends on the card you use. At full size (-d 1)
you get these image sizes: BUZ and LML33: 720x576, the DC10: 768x576
Other example:
> lavrec -w -f a -i S -d 2 -l -1 record%02d.avi
Should start recording,
-w
Waits for user confirmation to start (press enter)
-f a
use AVI as output format,
-i S
use SECAM SVHS-Input (SECAM Composite recording is also possible: -i s)
-d 2
the size of the pictures are half size
-l -1
do not touch the mixer settings
record%02d.avi
Here lavrec creates the first file named record00.avi after the file
has reached a size of 1.6GB (after about 20 Minutes recording) it
starts a new sequence named record01.avi and so on till the recording
is stopped or the disk is full
Other example:
> lavrec -f a -i t -q 80 -d 2 -C europe-west:SE20 test.avi
Should start recording now,
-f a
use AVI as output format,
-i t
use tuner input,
-q 80
set the quality to 80% of the captured image
-d 2
the size of the pictures are half size (352x288)
-C
choose TV channels, and the corresponding -it and -iT (video source: TV
tuner) can currently be used on the Marvel G200/G400 and the Matrox
Millenium G200/G400 with Rainbow Runner extension (BTTV-Support is
under construction). For more information on how to make the TV tuner
parts of these cards work, see the Marvel/Linux project on:
Last example:
> lavrec -f a -i p -g 352x288 -q 80 -s -l 70 -R l --software-encoding
test03.avi
The two new options are -g 352x288, which sets the size of the video to
be recorded when using --software-encoding, this enables the software
encoding of the recorded images. With this option you can also record
from a bttv based card. The processor load is high. This option only
works for generic video4linux cards (such as the brooktree-848/878
based cards), it doesn't work for zoran-based cards.
Other recording hints
All lavtools accept a file description like file*.avi, so you do not
have to name each file, but that would also be a posibillity to do.
Note: More options are described in the man-page, but with this you
should be able to get started.
Here are some hints for sensible settings. Turn the quality to 80% or
more for -d 2 capture. At full resolution as low as 40% seems to be
visually ”perfect”. -d 2 is already better than VHS video (a *lot*!).
For a Marvel you should not set the quality higher than 50 when you
record at full size (-d 1). If you use higher settings (-q 60) it is
more likely that you will encounter problems. Higher settings will
result in framedrops. If you're aiming to create VCD's then there is
little to be gained recording at full resolution as you need to reduce
to -d 2 resolution later anyway.
you can record at other sizes than the obvious -d 1/2/4. You can use
combinations where you use halve horizontal size and full vertical
size: -d 21. This would record for NTSC at a size of 352x480. This
helps if you want to create SVCDs, scaling the 352 Pixles put to 480 is
not that visible for the eye as if you would use the other combination
-d 12. Where you have the full horzontal resolution and half vertical
this Version will have a size of 720x288 for NTSC
Some information about the typical lavrec output while recording
0.06.14:22 int: 00040 lst:0 ins:0 del:0 ae:0 td1=0.014 td2=0.029
The first part shows the time lavrec is recording. int: the interval
between two frames. lst: the number of lost frames. ins and del: are
the number of frames inserted and deleted for sync correction. ae: num-
ber of audio errors. td1 and td2 are the audio/video time-difference.
(int) frame interval should be around 33 (NTSC) or 40 (PAL/SECAM). If
it is very different, you'll likely get a bad recording and/or many
lost frames
(lst) lost frames are bad and mean that something is not working very
well during recording (too slow HD, too high CPU usage, ...) Try
recording with a greater decimation and possibly a lower quality.
(ins, del) inserted OR deleted frames of them are normal → sync. If you
have many lost AND inserted frames, you're asking too much of your
machine. Use less demanding options or try a different sound card.
(ae) audio errors are never good. Should be 0
(td1, td2) time differenceis always floating around 0, unless sync cor-
rection is disabled (--synchronization!=2, 2 is default).
Notes about ”interlace field order - what can go wrong and how to fix it”
Firstly, what does it mean for interlace field order to be wrong?
The whole mjpegtools image processing chain is frame-oriented. Since it
is video material that is captured each frame comprised a top field
(the 0th, 2nd, 4th and so lines) and a bottom field (the 1st, 3rd, 5th
and so on lines).
There are three bad things that can happen with fields
This is really only an issue for movies in PAL video where each film
frame is sent as a pair of fields. These can be sent top or bottom
field first and sadly it's not always the same, though bottom-first
appears to be usual. If you capture with the wrong field order (you
start capturing each frame with a bottom rather than a top or vice
versa) the frames of the movie get split *between* frames in the
stream. Played back on a TV where each field is displayed on its own
this is harmless. The sequence of fields played back is exactly the
same as the sequence of fields broadcast. Unfortunately, playing back
on a Computer monitor where both fields of a frame appear at once it
looks *terrible* because each frame is effectively mixing two moments
in time 1/25sec apparent.
The two fields can simply be swapped somehow so that top gets treat as
bottom and bottom treat as top. Juddering and ”slicing” is the result.
This occasionally seems to happen due to hardware glitches in the cap-
ture card.
Somewhere in capturing/processing the *order* in time of the two fields
in each frame can get mislabeled somehow. This is not good as it means
that when playback eventually takes place a field containing an image
sampled earlier in time comes after an image sampled later. Weird
”juddering” effects are the results.
How can I recognize if I have one of these Problems ?
This can be hard to spot. If you have mysteriously flickery pictures
during playback try encoding a snippet with the reverse field-order
forced (see below). If things improve drastically you know what the
problem was and what the solution is!
The two fields can simply be swapped somehow so that top gets treat as
bottom and bottom treat as top. Juddering and ”slicing” is the result.
This occasionally seems to happen due to hardware glitches in the cap-
ture card. That problem lookes like that:
Interlacing problem
Somewhere in capturing/processing the *order* in time of the two fields
in each frame can get mislabeled somehow. This is not good as it means
that when playback eventually takes place a field containing an image
sampled earlier in time comes after an image sampled later. Weird ”jud-
dering” effects are the result.
If you use glav or lavplay be sure that you also use the -F/--flicker
option. This disables some things that make the picture look better.
If you want to look at the video you can also use yuvplay:
> lav2yuv │ ... │ yuvplay
If there is a field order problem you should see it with yuvplay.
How can you fix it?
To fix this one the fields need to be ”shifted” through the frames. Use
yuvcorrect's -T BOTT_FORWARD/TOP_FORWARD to shift the way fields are
allocated to frames. You can find out the current field order for an
MJPEG file by looking at the first few lines of debug output from: >
lav2yuv -v 2 the_mjpeg_file > /dev/null Or re-record exchanging -f a
for -F A or vice-versa.
This isn't too bad either. Use a tool that simply swaps the top and
bottom fields a second time. yuvcorrect can do this use the -T
LINE_SWITCH.
Is easy to fix. Either tell a tool someplace to relabel the fields or
simply tell the player to play back in swapped order (the latter can be
done ”indirectly” by telling mpeg2enc when encoding to reverse the flag
(-z b│t) that tells the decoder which field order to use.
In order to determine exactly what type of interlacing problem you
have, you need to extract some frames from the recorded stream and take
a look at them:
> mkdir pnm
> lav2yuv -f 40 video.avi │ y4mtoppm │ pnmsplit - pnm/image%d.pnm
> rm pnm/image?.pnm
> cd pnm
> xv
First we create a directory where we store the images. The lav2yuv -f
40 writes only the first 40 frames to stdout. The mjpegtools y4mtoppm
converts the frames to pnm images and the pnmsplit splits the picture
into two frames in the picture to two single pictures. Then we remove
the first 10 images because pnmsplit does not support the %0xd number-
ing. Without a leading zero in the number, the files will be sorted in
the wrong order, leading to confusing playback.
Use your favorite graphic program (xv for example) to view the pic-
tures. As each picture only contain one field out of two they will
appear scaled vertically. If you look at the pictures you should see
the movie slowly advancing.
If you have a film you should always see 2 pictures that are nearly the
same (because the film frame is split into two field for broadcasting)
after each other. You can observe this easily if you have comb effects
when you pause the film because both fields will be displayed at the
same time. The two pictures that belong together should have an even
number and the following odd number. So if you take a look on pictures:
4 and 5 are nearly identical, 5 and 6 differ (have movement), 6 and 7
identical, 7 and 8 differ , ....
To fix this problem you have to use yuvcorrect's -T BOTT_FORWARD or
TOP_FORWARD. You can also have the problem that the field order
(top/bottom) is still wrong. You may have to use yuvcorrect a second
time with -M LINE_SWITCH, or use the mpeg2enc -z (b│t) option.
To see if you guessed correctly, extract the frames again, reordering
them using yuvcorrect:
> lav2yuv -f 40 video.avi │ yuvcorrect -T OPTION │ y4mtoppm │ pnmsplit
- pnm/image%d.pnm
Where ”OPTION” is what you think it will corrects the problem. This is
for material converted from film. Material produced directly for TV is
addressed below.
Hey, what about NTSC movies ?
Movies are broadcast in NTSC using ”3:2” pulldown which means that half
the capture frames contain fields from 1 movie frame and half fields
from 2 frames. To undo this effect for efficient MPEG encoding you need
to use yuvkineco.
If you have an interlaced source like a TV camera you have a frame con-
sists of two fields that are recorded at different points in time and
shown after each other. Spotting the problem here is harder. You need
to find something moving horizontally from the left to the right. When
you extract the fields, the thing should move in small steps from the
left to the right, not one large step forward, small step back, large
forward, small back...... You have to use the same options mentioned
aboth to correct the problem.
Do not expect that the field order is always the same (top- or bottom-
first) It may change between the channels, between the films, and it
may even change within a film. If it changes constant you may have to
encode with the mpeg2enc -I 1 or even -I 2.
You can only have this problems if you record at full size !!!
Creating videos from other sources
Here are some hints and descriptions of how to create the videos from
other sources like images and other video types.
You might also be interested in taking a look at the Transcoding of
existing MPEG-2 section.
Creating videos from images
You can use jpeg2yuv to create a yuv stream from separate JPEG images.
This stream is sent to stdout, so that it can either be saved into a
file, encoded directly to a mpeg video using mpeg2enc or used for any-
thing else.
Saving an yuv stream can be done like this:
> jpeg2yuv -f 25 -I p -j image%05d.jpg > result.yuv
Creates the file result.yuv containing the yuv video data with 25 FPS.
The -f option is used to set the frame rate. Note that image%05d.jpg
means that the jpeg files are named image00000.jpg, image00001.jpg and
so on. (05 means five digits, 04 means four digits, etc.) The -I p is
needed for specifing the interlacing. You have to check which type you
have. If you don't have interlacing just choose p for progressive
If you want to encode a mpeg video directly from jpeg images without
saving a separate video file type:
> jpeg2yuv -f 25 -I p -j image%05d.jpg │ mpeg2enc -o mpegfile.m1v
Does the same as above but saves a mpeg video rather than a yuv video.
See mpeg2enc section for details on how to use mpeg2enc.
You can also use yuvscaler between jpeg2yuv and mpeg2enc. If you want
to create a SVCD from your source images:
> jpeg2yuv -f 25 -I p -j image%05d.jpg │ yuvscaler -O SVCD │ mpeg2enc
-f 4 -o video.m2v
You can use the -b option to set the number of the image to start with.
The number of images to be processed can be specified with the -n num-
ber. For example, if your first image is image01.jpg rather than
image00.jpg, and you only want 60 images to be processed type:
>jpeg2yuv -b 1 -f 25 -I p -n 60 -j image*.jpg │ yuv2lav -o stream_with-
out_sound.avi
Adding the sound to the stream then:
> lavaddwav stream_without_sound.avi sound.wav stream_with_sound.avi
For ppm input there is the ppmtoy4m util. There is a manpage for ppm-
toy4m that should be consulted for additional information.
So to create a mpeg video try this:
>cat *.ppm │ ppmtoy4m -o 75 -n 60 -F 25:1 │ mpeg2enc -o output.m1v
Cat's each *.ppm file to ppmtoy4m. There the first 75 frames (pictures)
are ignored and next 60 are encoded by mpeg2enc to output.m1v. You can
run it without the -o and -n option. The -F options sets the frame
rate, default is NTSC (30000:1001), for PAL you have to use -F 25:1.
Other picture formats can also be used if there is a converter to ppm.
>ls *.tga │ xargs -n1 tgatoppm │ ppmtoy4m │ yuvplay
A list of filenames (ls *.tga) is given to xargs that executes the
tgatoppm with one (-n 1) argument per call, and feeds the output into
ppmtoy4m. This time the video is only shown on the screen. The xargs
is only needed if the converter (tgatoppm), can only operate on a sin-
gle image at a time.
If you want to use the ImageMagick 'convert' tool (a Swiss Army Knife)
try:
>convert *.gif ppm:- │ ppmtoy4m │ yuvplay
That means take all '.jpg' images in directory, convert to PPM format,
and pipe to stdout, then ppmtoy4m processes them ....
Decoding streams with mplayer
Decoding the streams with mplayer is a nice way of bringing every video
that mplayer can play back to something you can edit or encode directly
to a mpeg video with the mjpegtools. This method works with mplayer
1.0pre2 or newer
>mkfifo stream.yuv
>mplayer -nosound -noframedrop -vo yuv4mpeg anyfile.mpg &
>cat stream.yuv │ yuv2lav -o mjpeg_wo.avi
>mplayer -vo null -ao pcm -aofile anyfile.wav anyfile.mpg
Now you have for example a mjpeg encoded AVI without sound. The sound
will be in anyfile.wav. Now you can choose if you want to add the sound
to the AVI with lavaddwav and edit the file and encode it.
You can also use instead of yuv2lav, mpeg2enc or any other tool from
the mjpeg tools so your command might also look like that:
> cat stream.yuv │ yuvdenoise │ yuvscaler -O SVCD │ mpeg2enc -f 4 -o
video_svcd.m2v
And cat the wav file into mp2enc to encode it to MP2 audio. The -vo
yuv4mpeg option works well with other input types mentioned in the
mplayer documentation.
Decoding MPEG2 streams with mpeg2dec
You can decode mpeg2 streams with the patched mpeg2dec version which
creates yuv streams. You can pipe that into any other mjpegtools pro-
gram. Or you use a mpeg2dec version directly from the libmpeg2
project and use the output mode pgmpipe. With the pgmtoy4m program from
the mjpegtools you can convert that pgm output back to yuv.
If you ask yourself why there is a patched version and pgmtoy4m. The
answer is that the patch for yuv output was sent several times to the
libmpeg2 developers but was never included. Now we have two ways
around that problem. Decoding looks like this:
> mpeg2dec -s -o pgmpipe ANYTS.VOB │ pgmtoy4m -i t -a 10:11 -r
30000:1001 │ mpeg2enc -f 8 newvideo.m2v
You can decode the audio as described in the Transcoding of existing
MPEG-2 Section.
Other things to know
If you have Transport Streams from your DVB card, or os Satelite
Receiver you might want to demultiplex or cut them. A nice tool for
that is Project X available from:
You can process the streams afterwards as you would do with any mpeg
movie or demultiplexed audio video. So the Transcoding of existing
MPEG-2 section of this document will be of interest.Checking if record-
ing was successful
You can use lavplay or glav. IMPORTANT: NEVER try to run xawtv and lav-
play or glav with hardware playback, it will not work. For software
playback it works fine.
>lavplay -p S record.avi
You should see the recorded video and hear the sound. But the decoding
of the video is done by the CPU which will place a heavy load on the
system. The advantage of this method is you don't need xawtv.
The better way:
>lavplay -p H record.avi
The video is decoded and played by the hardware. The system load is now
very low. This will play it back on-screen using the hardware rather
than software decoding.
You might also try:
> lavply -p C record.avi
Which will play it back using the hardware but to the video output of
the card.
> glav record.avi
Does the same as lavplay but you have an nice GUI. The options for glav
and lavplay are nearly the same. Using no option SW playback is used.
Using hardware playback a signal for the Composite and SVHS OUT is gen-
erated so you can view the movie on your TV.
> lav2yuv test.eli │ yuvplay
Is a other way to get the video without sound. You can use yuvplay once
in the encoding command. When you use yuvplay in the encoding command
you see the changes made by filters and scaling. You can also use it
for slow-motion debugging.
NOTE: After loading the driver's you have to start xawtv to set up some
things lavplay and glav do not, but they are needed for HW-Playback.
Don't forget to close xawtv !!
NOTE2: Do not try to send glav an lavplay into background, wont work
correct !!!
NOTE3: SECAM playback is now (12.3.2001) only in monochrome, but the
recording and encoding is done right.
NOTE4:Bad cables may reduce the quality of the image. Normally you
can't see this but when there is text you might notice a small shadow.
When you see this you should change the cable.
Coming soon: There is a tool which makes recoding videos very simple:
Linux Studio. You can download it at:
Edit the video
Edit with glav
Most tasks can be easily done by glav. Like deleting parts of the
video, cut paste and copy parts of the videos.
glav button description
The modifications should be saved because glav does not destructively
edit the video. This means that the original video is left untouched
and the modifications are kept in an extra ”Edit List” file readable
with a text editor. These files can be used as an input to the other
lavtools programs such as lav2wav, lav2yuv, lavtrans.
If you want to cut off the beginning and the end of the stream mark the
beginning and the and, and use the ”save select” button. The edit list
file is than used as input for the lavtools. If you want to split a
recorded video to some smaller parts simply select the parts and then
save each part to a different listfile.
You can see all changes to the video and sound NOW and you do not need
to recalculate anything.
If you want to get a "destructive" version of your edited video use:
> lavtrans -o short_version.avi -f a editlist.eli
-o
specifies the output name
-f a
specifies the output format (AVI for example)
editlist.eli
is the list file where the modifications are described. You generate
the list file with the "save all" or ”save select” buttons in glav.
Unify videos
> lavtrans -o stream.qt -f q record_1.avi record_2.avi ... record_n.avi
-o
specifies the outputfile name
-f q
specifies the output format, quicktime in this case
This is usually not needed. Keep in your mind that there is the 2GB
file-size-limit on 32Bit systems with an older glibc.
Separate sound
> lavtrans -o sound.wav -f w stream.avi
Creates a wav file with the sound of the stream.avi Maybe needed if you
want to remove noise or if you want to convert it to another sound for-
mat.
Another way to split the sound is:
> lav2wav editlist.eli >sound.wav
Separate images
>mkdir jpg; lavtrans -o jpg/image%05d.jpg -f i stream.avi
First create the directory ”jpg”. Then lavtrans will create single JPG
images in the jpg directory from the stream.avi file. The files will be
named: image00000.jpg, image00001.jpg ....
The jpg images created contain the whole picture. But if you have
recorded at full size the images are stored interlaced. Usually the
picture viewers show only the first field in the jpg file.
If you want to have the image in a single file you can use that version
> lav2yuv -f 1 stream.avi │ y4mtoppm -L >file.pnm
If you want to split the fields into single files use that:
> lav2yuv -f 5 ../stream.avi │ y4mtoppm │ pnmsplit - image%d.pnm
Maybe interesting if you need sample images and do not want to play
around with grabbing a single image.
Creating movie transitions
Thanks to Philipp Zabel's lavpipe, we can now make simple transitions
between movies or combine multiple layers of movies.
Philipp wrote this HOWTO on how to make transitions:
Let's assume simple this scene: We have two input videos intro.avi and
epilogue.mov and want to make intro.avi transition into epilogue.mov
with a duration of one second (that is 25 frames for PAL or 30 frames
for NTSC).
Intro.avi and epiloque.mov have to be of the same format (the same
frame rate and resolution). In this example they are both 352x288 PAL
files. intro.avi contains 250 frames and epilogue.mov is 1000 frames
long.
Therefore our output file will contain:
the first 225 frames of intro.avi
a 25 frame transition containing the last 25 frames of intro.avi and
the first 25 frames of epilogue.mov
the last 975 frames of epilogue.mov
We could get the last 25 frames of intro.avi by calling:
>lav2yuv -o 225 -f 25 intro.avi
-o 255, the offset, tells lav2yuv to begin with frame # 225 and
-f 25 makes it output 25 frames from there on.
Another possibility is:
> lav2yuv -o -25 intro.avi
Since negative offsets are counted from the end.
And the first 25 frames of epilogue.mov:
> lav2yuv -f 25 epilogue.mov
-o defaults to an offset of zero
But we need to combine the two streams with lavpipe. So the call would
be:
> lavpipe ”lav2yuv -o 255 -f 25 intro.avi” ”lav2yuv -f 25 epilogue.mov”
The output of this is a raw yuv stream that can be fed into tran-
sist.flt.
transist.flt needs to be informed about the duration of the transition
and the opacity of the second stream at the beginning and at the end of
the transition:
-o num
opacity of second input at the beginning [0-255]
-O num
opacity of second input at the end [0-255]
-d num
duration of transition in frames
An opacity of 0 means that the second stream is fully transparent (only
stream one visible), at 255 stream two is fully opaque.
In our case the correct call (transition from stream 1 to stream 2)
would be:
> transist.flt -o 0 -O 255 -d 25
The -s and -n parameters equate to the -o and -f parameters of lav2yuv
and are only needed if anybody wants to render only a portion of the
transition for whatever reason. Please note that this only affects the
weighting calculations - none of the input is really skipped. If you
use the skip parameter (-s 30, for example) you also need to skip the
first 30 frames in lav2yuv (-o 30) in order to get the expected result.
If you didn't understand this send an email to the authors or simply
ignore -s and -n. The whole procedure will eventually be automated.
Now we want to compress the yuv stream with yuv2lav:
> yuv2lav -f a -q 80 -o transition.avi
Reads the yuv stream from stdin and outputs an avi file (-f a) with
compressed jpeg frames of quality 80.
Now we have the whole command for creating a transition:
> ypipe ”lav2yuv -o 255 -f 25 intro.avi” ”lav2yuv -f 25 epilogue.mov” │
transist.flt -o 0 -O 255 -d 25 │ yuv2lav -f a -q 80 -o transition.avi
The resulting video can be written as a LAV Edit List, a plain text
file containing the following lines:
LAV Edit List
PAL
3
intro.avi
transition.avi
epilogue.mov
0 0 224
1 0 24
2 25 999
This file can be fed into glav or lavplay, or you can pipe it into
mpeg2enc with lav2yuv or combine the whole stuff into one single mjpeg
file with lavtrans or lav2yuv│yuv2lav.
Converting the stream to MPEG or DIVx videos
First there is some general description in the encoding process and
afterwards there is a detailed description of some commonly used output
formats.
If you want a one command conversation to mpeg videos try lav2mpeg in
the scripts directory
The encoding with the lav2mpeg script looks like this for mpeg1 output:
>lav2mpeg -a 160 -b 2110 -d 320x240 -m mpeg1 -o output.mpg file.eli
Will create a mpeg1 with videobitrate of 2110kBit/sec and audiobitrate
of 160 kBit/sec
at a resolution of 320x240
Or for the generation of mpeg2 output:
lav2mpeg -o mpeg2 -O output.mpg file.eli
Will create a mpeg2 with default bitrate in same resolution as the
input resolution
Better results can be accomplished, however, by trying various options
and find out which ones work best for you. These are discussed below.
The creation of MPEG1 movies is explained with more examples and in
greater detail because most of the things that can be used for MPEG1
also work for the other output formats
For the creation of of VCD/SVCD Stills sequences (-f 6, -f 7 in
mpeg2enc) you should see:
Still sequences are needed for the creation of menus in VCD/SVCD. The
creation of menus is described in the doku of vcdimager.
Creating sound
MPEG-1 videos need MPEG1-layer2 sound files. For MPEG-2 videos you can
use MPEG1-Layer2 and MPEG1-Layer3 (MP3). Layer 3 (MP3) audio is not
an offically valid audio format but many VCD players will recognize it.
MP3 audio is not valid for DVDs. You should stick to MPEG1-Layer2
because most of the MPEG2 players (DVD Player for example usually the
different Winxx Versions have great problems with this too) are not
able to play MPEG2-Video and MPEG1-Layer3 sound.
mp2enc is a MPEG1-layer 2 Audio encoder. The toolame encoder is also
able to produce an layer 2 file. You can use that one as well.
Toolame is much faster than mp2enc but toolame does not peform resam-
pling (48000 to 44100 samples/second). Many hardware players will play
SVCDs using 48000 rate audio. For mp3 creation I'm be sure you have an
encoder.
Example:
> lav2wav stream.avi │ mp2enc -o sound.mp2
This creates a mpeg sound file out of the stream.avi with 224kBit/sec
bitrate and a sample rate of 48kHz. If you audio file has 44.1kHz
mp2enc resamples the audio to create a 48kHz output. If you want a
44.1kHz output sample rate you have to add -r 44100 to the mp2enc com-
mand
Example
> cat sound.wav │ mp2enc -v 2 -V -o sound.mp2
This creates a VCD (-V bitrate=224, stereo, sampling rate:44100) com-
patible output from the wav file.
With -v 2 mp2enc is more verbose, while encoding you see the number of
sec of audio already encoded.
You can test the output with:
> plaympeg sound.mp2
NOTE: plaympeg is a MPEG1 Player for Linux, you can use other players
as well, for MPEG audio testing you can also use mpg123.
Converting video
You can create MPEG1 and MPEG2 videos.
Normally the first video you create is not the best. For optimal qual-
ity/size you need to play with the bitrate, search radius, noise filter
.... The options of mpeg2enc are described in the manpage of mpeg2enc.
Example:
lav2yuv stream.avi stream1.avi │ mpeg2enc -o video.m1v
This creates an video file with the default constant bitrate of
1152kBit/sec. This is the bitrate you need if you want to create VCDs.
You can specify more files and also use the placeholder %nd. Where n
describes the number.
Example:
> lav2yuv streami%02d.avi │ mpeg2enc -b 1500 -r 16 -o video.m1v
mpeg2enc creates a video with a bitrate of 1500kBit/s uses an search
radius of 16. That means when trying to find similar 16*16 macroblocks
of pixels between frames the encoder looks up to 16 pixels away from
the current position of each block. It looks twice as far when compar-
ing frames 1 frame apart and so on. Reasonable values are 16 or 24. The
default is 16 so adding the option here is silly. Lower values (0, 8),
improve the encoding speed but you get lower quality (more visible
artifacts) while higher values (24, 32) improve the quality at the cost
of the speed. With the file description of stream%02d.avi all files are
processed that match this pattern with 00, 01....
Scaling
Using yuvscaler one can now also scale the video before encoding it.
This can be useful for users with a DC10 or DC10+ cards which captures
at -d 1 768x576 or -d 2 384x288 (PAL/SECAM) or -d 1 640x480 (NTSC).
You get a full description of all commands by reading the manpage or
running:
>yuvscaler -h
Example:
> lav2yuv stream.avi │ yuvscaler -O VCD │ mpeg2enc -o video.m1v
This will scale the stream to VCD size which for PAL/SECAM is 352x288
and for NTSC is 352x240. The scaled yuvstream is encoded to MPEG-1.
It can also do SVCD scaling to 480x480 (NTSC) or 480x576 (PAL/SECAM):
> lav2yuv stream.avi │ yuvscaler -O SVCD -M BICUBIC │ mpeg2enc -o
video.m1v
The mode keyword (-M) forces yuvscaler to use the higher quality bicu-
bic algorithms for downscaling and not the default resample algorithms.
Upscaling is always done using the bicubic algorithm.
Example
> lav2yuv stream.avi │ yuvscaler -I USE_450x340+20+30 -O SIZE_320x200 │
mpeg2enc -o video.m1v
Here we only use a part of the input and specify a nonstandard output
resolution.
NOTE: yuvscaler can set a active area, and set everything else to black
using: -I ACTIVE_WidthxHeight+WidthOffset+HeightOffset
Testing is done by:
> plaympeg video.m1v
NOTE:These are only examples. There are more options you can use. You
can use most of them together to create high quality videos with the
lowest possible bitrate.
NOTE2:The higher you set the search radius the longer the conversion
will take. In general the more options used the longer encoding takes.
NOTE3:MPEG1 was not designed to be a VBR (variable bitrate stream) !!
So if you encode with -q 15 mpeg2enc sets the maximal bitrate -b to
1152. If you want a VBR MPEG1 you have to set -b very high (2500).
NOTE4:Maybe you should give better names than video.mpg. A good idea is
to use the options as part of the filename (for example:
video_b1500_r16_41_21.m1v). Another possibility is to call all the
layer 2 files ”.mp2” all the MPEG-1 video files ”.m1v” and all MPEG-2
video files ”.m2v” Easy to see what's happening then. Reserve .mpg for
multiplexed MPEG-1/2 streams.
Putting the streams together
Example:
> mplex sound.mp2 video.m1v -o my_video.m1v
Puts the sound.mp2 and the video.m1v stream together to my_video.mpg
Now you can use your preferred MPEG player and watch it. All players
(gtv for example) based on the SMPEG library work well for MPEG-1.
Other players (which can play MPEG-2 as well as MPEG-1 movies) are:
xmovie, xine, and MPlayer.
NOTE: If you have specified the -S option for mpeg2enc mplex will auto-
matically split the files if there is in the output filename a %d
(looks like: -o test%d.mpg) The files generated this way are separate
stand-alone MPEG steams!
NOTE2: xine might have a problem with seeking through videos. mplayer
has a problem with the ”seek backward/forward” with variable bitrate
streams because it goes forward in the file the amount of data for a
constant bitrate stream. That amount might be significantly more than
10 seconds or one minute (those are the amount mplayer seeks for each
press of the arrow keys). So don't wonder if it seeks much more time
forward or backward than you expect.
Variable bit-rate multiplexing: Remember to tell mplex you're encoding
VBR (-V option) as well as mpeg2enc (see the example scripts). It
*could* auto-detect but it is not working yet. You should tell mplex a
video buffer size at least as large as the one you specified to
”mpeg2enc” Sensible numbers for MPEG-1 might be a ceiling bit-rate of
2800Kbps, a quality ceiling (quantization floor) of 6 and a buffer size
of 400K.
Example:
> mplex -V -r 1740 audio.mp2 video_vbr.m1v -o vbr_stream.mpg
Here we multiplex a variable bitrate stream. mplex is now a single pass
multiplexer so it can't detect the maximal bitrate and we have to spec-
ify it. The data rate for the output stream is: audio bitrate + peak
videobitrate + 1-2% for mplex information. If audio (-b 224) has
224kBit, video has 1500kBit (was encoded with -b 1500 -q 9) then we
have 1724 * 1.01 or about 1740kBit.
Example:
> plaympeg my_video.mpg
or
> gtv my_video.mpg
Creating MPEG1 Videos
For MPEG1 you can use mpeg layer 2 Audio and mpeg1 video. A subset of
MPEG1 movies are VCD's. You can use VBR (Variable BitRate) for the
Video (although VCDs are almost always use CBR video) but the Audio has
to be CBR (Constant BitRate).
MPEG1 is recommended for picture sizes up to 352x288 for PAL and
352x240 for NTSC for larger sizes MPEG2 is the better choice. There is
no exact resolution where MPEG1 is better than MPEG2. Just to make
soure, MPEG1 can't handle interlaced sources. If you video is inter-
laced you need MPEG2 to get it proper encoded. .
MPEG1 Audio creation Example
> lav2wav editlist.eli │ mp2enc -r 44100 -o sound.mp2
You can save some bits by telling mp2enc to use a lower bitrate (-b
option) like 160 or 192 kBit/s. The -r 44100 option forces mp2enc to
generate a 44.1kHz audio file.
> lav2wav editlist.eli │ mp2enc -b 128 -m -o sound.mp2
This creates a mono output with an bitrate of 128kBit/sec bitrate. The
input this time is the editlistfile (can have any name) created with
glav so all changes you made in glav are direct processed and handed
over to mp2enc. You do NOT have to create an edited stream with lav-
trans to get it converted properly.
MPEG1 Video creation Example
> lav2yuv editlist.eli │ mpeg2enc -b 2000 -r 24 -q 6 -o video.m1v
mpeg2enc creates an video with an bitrate of 2000kBit/s (or
2048000Bit/s) but the -q flag activates the variable bitrate and a
quality factor of 6. It uses a search radius of 24.
Explanation:when mpeg2enc is invoked without the 'q' flag it creates
”constantbit-rate” MPEG streams. Where (loosely speaking) the strength
of compression (and hence picture quality) is adjusted to ensure that
on average each frame of video has exactly the specified number of
bits. Such constant bit-rate streams are needed for broadcasting and
for low-cost hardware like DVD and VCD players which use slow fixed-
speed player hardware.
Obviously this is fairly inefficient as it means inactive scenes use up
bits that could better be ”spent” on rapidly changing scenes. Setting
the 'q' flag tells mpeg2enc to generate variable bit-rate streams. For
such streams the bit-rate specified is simply the maximum permissible.
The 'q' parameter specifies the minimum degree of compression to be
applied by specifying how exactly picture information is recorded. Typ-
ically, 'q' would be set so that quiet scenes would use less than the
specified maximum (around 6 or 8) but fast moving scenes would still be
bit-rate limited. For archival purposes setting a maximum bit-rate high
enough never to be reached (e.g. 10Mbps) and a q of 2 or 3 are reason-
able choices.
Example:
> lav2yuv stream.avi │ yuvscaler -I ACTIVE_352x240+0+24 │ mpeg2enc -b
1152 -r 16 -4 1 -2 1 -o video.m1v
Usually there is at the top and at the bottom a nearly black border and
a lot of bandwidth is used for something you do not like. The yuvscaler
-I ACTIVE option sets everything that is not in the described area to
black, but the imagesize (352x288) is not changed. So you have a real
black border the encoder only uses a few bits for encoding them. You
are still compatible with the VCD's format in this example. To deter-
mine the active window extract one frame to the jpeg format:
> lavtrans -f i -i 100 -o frame.jpg test.avi
Than use your favorite graphic display program to determine the active
size. The -4 1 and -2 1 options improves the quality about 10% but
conversion is slower.
At the size of 352x288 (1/2 PAL size, created when using the -d 2
option when recording) the needed bitrate is/should be between 1000 -
1500kBit/s. For NTSC it should be about the same, because the image is
smaller, but there are more frames per second than in PAL.
Anyways, the major factor is quality of the original and the degree of
filtering. Poor quality unfiltered material typically needs a higher
rate to avoid visible artifacts. If you want to reduce bit-rate with-
out annoying artifacts when compressing broadcast material you should
try one (or more) of the noise filters.
Example:
> lav2yuv stream.avi │ mpeg2enc -b 1500 -n s -g 6 -G 20 -P -o video.m1v
Here the stream.avi will be encoded with:
-b 1500
a Bitrate of 1500kBit/sec
-n s
the input Video norm is forced to SECAM
-P
This ensures that 2 B frames appear between adjacent I/P frames.
Several common MPEG-1 decoders can't handle streams that do not have 2
B-frames between I/P frames
-g 6 -G 20
the encoder can dynamically change the group-of-pictures size to
reflect scene changes. This is done by setting a maximum GOP (-G flag)
size larger than the minimum (-g flag). For VCDs sensible values might
be a minimum of 9 and a maximum of 15. For SVCD 9 and 15 would be good
values. If you only want to play it back on SW player you can use other
min-max values.
Example
> lav2yuv stream*.avi │ mpeg2enc -b 1500 -r 16 -4 1 -2 1 -S 630 -B 260
-o video_n1_1500_r16_41_21_S630_B240.m1v
lav2yuv processes all the stream files. Then mpeg2enc is given some
options that make the encoded stream look nicer. Using -S 630 means
that mpeg2enc marks the stream so that mplex generates a new stream
every 630MB. One important thing is the use of the -B option which
specifies the non-video (audio and mplex information) bitrate. The -B
value of 260 should be fine for audio with 224kBit and mplex informa-
tion. For further information take a look at the encoding scripts in
the scripts directory.
MPEG1 Multiplexing Example
Example
>mplex sound.mp2 video.m1v -o my_video.mpg
Puts the sound.mp2 and the video.m1v stream together to my_video.mpg.
It only works that easy if you have CBR (the -q option was not used
with mpeg2enc).
Example
mplex -V -r 1740 audio.mp2 video_vbr.m1v -o vbr_stream.mpg
Here we multiplex a variable bitrate stream. mplex is now a single pass
multiplexer so it can't detect the maximal bitrate and we have to spec-
ify it. The data rate for the output stream is: audio bitrate + peak
videobitrate + 1-2% for mplex information. If audio (-b 224) has
224kBit, video has 1500kBit (was encoded with -b 1500 -q 9) then we
have 1724 * 1.01 or about 1740kBit.
Creating MPEG2 Videos
MPEG2 is recommended for sources with a greater picture than 352x240
for NTSC and 352x288 for PAL. MPEG2 can also handle interlaced sources
like recording from TV at full resolution.
MPEG2 allows the usage of mpeg layer 3 (mp3) sound. So you can use your
favorite mp3encoder for the creation of the sound. However, MP3 audio
is not valid for DVDs. It is best to use MP2 (Layer 2) audio. The
audio can also be a VBR Stream.
MPEG2 is usually a VBR Stream. MPEG2 creation with optimization
requires a lot of CPU power. A film with the double resolution is NOT
4 times larger than an MPEG1 Stream. Depending on your quality settings
it will be about 1.5 up to 3 times larger than the MPEG1 Stream at its
lower resolution.
MPEG2 Audio creation Example
> lav2wav editlist.eli │ mp2enc -o sound.mp2
This will fit the MPEG2 quite well. You can save some bits by telling
mp2enc to use a lower bitrate (-b option) like 160 or 192 kBit/s. And
might want to add -r 44100 so that mpeg2enc generates a 44.1kHz sam-
pling rate audio file. I hope I don't need to explain the usage of an
MP3 Encoder. But you should not use all the fancy options that are
available.
MPEG2 Video creation Example
> lav2yuv editlist.eli │ mpeg2enc -f 3 -b 3000 -q 9 -o video.m2v
A very simple example for MPEG2 Video. The most important option is
the -f 3. That tells mpeg2enc that it should create a MPEG2 stream.
Because it is a generic MPEG2 you have to use the -b bitrate options.
And should use the -q option because you usually want a space saving
VBR Stream. When using VBR streams the -b option tells mpeg2enc the
maximum bitrate that can be used. The -q option tell mpeg2enc what
quality the streams should have. The bitrate has an upper bound of the
value specified by -b.
> lav2yuv editlist.eli │ mpeg2enc -f 3 -4 1 -2 1 -q7 -b 4500 -V 300 -P
-g 6 -G 18 -I 1 -o video.m2v
This will generate a higher quality MPEG2 stream because the -4 1 and
-2 1 options were used. With -b 4500 -q 7 you tell mpeg2enc the maxi-
mal bitrate and the quality factor. -V is the video buffer size used
for decoding the stream. For SW playback it can be much higher than the
default. Dynamic GOP is set with -g and -G. A larger GOP size can help
reduce the bit-rate required for a given quality but very large sizes
can introduce artifacts due to DCT/iDCT accumulated rounding errors.
The -P option also ensures that 2 B frames appear between adjacent I/P
frames. The -I 1 option tells mpeg2enc that the source is a interlaced
material like videos. There is (time consuming) interlaced motion com-
pensation logic present in mpeg2enc. Mpeg2enc will use that logic if
the size of the frames you encode is larger than the VCD size for your
TV Norm.
If you deinterlacing the movie with yuvdeinterlace you should tell
mpeg2enc that it does not need to do motion estimation for interlaced
material. You have to use the -I 0 option of mpeg2enc to say that the
frames are already deinterlaced. This will save a lot of time when
encoding. If you don't use -I 0 it will not cause problems, the encod-
ing will just take longer.
You can also use scaling an options that optimize (denoise) the images
to get smaller streams. These options are explained in detail in the
following sections.Which values should be used for VBR Encoding
The -q option controls the minimum quantization of the output stream.
Quantization controls the precision with which image information is
encoded. The lower the value the better the image quality. Values
below 4 are extremes and should only be used if you know what you are
doing
Usually you have to set up a maximum bitrate with the -b option. The
tricky task is to set a value for the -q option and the -b option that
produces a nice movie without using too much bandwidth and does not
introduce too many artifacts.
A quality factor should be chosen that way that the mplex output of
Peak bit-rate and average bit-rate differ by about 20-25%. If the dif-
ference is very small (less than < 10%) it is likely that you will
begin to see artifacts in high motion scenes. The most common cause of
the average rate being too close (or equal) to the maximum rate is
wrong value for the maximal bitrate or a quality factor that is too
high.
A combination that will produce more artifacts than you can count is a
SVCD with a maximal video bitrate of 2500kBit and a qualitfactor set to
1 or 2. For SVCD with a video limit of 2500kBit a quality factor of
7-11 fits quite good (8 is the default). If you use filter programs or
have a very good source like digital TV, DVD like material or rendered
pictures you can use a quality factor of 6 when creating SVCDs. If
your SVCD/DVD player supports higher bitrates than the official
2788kBit/sec for the video and audio. When using a higher bitrate and
quality factor action scenes will look much better but of course the
playing time of the disc will be less.
The same (7-11) quality factor for a full size picture and a top
bitrate of 3500 to 4000 kBit will produce few artifacts.
For SVCD/DVD you can expect a result like the one described if the max-
imal bitrate is not set too low:
q <= 6 real sharp pictures, and good quality
q <= 8 good quality
q >= 10 average quality
q >= 11 not that good
q >= 13 here even still sequences might look blocky
Encoding destination TV (interlaced) or Monitor (progressive)
MPEG2 supports interlaced data in addition to the progressive format.
A MPEG2 movie can be interlaced or progressive. It depends on the
source (film or broadcast) and on the viewing device.
If you encode a film both fields should be the same. Deinterlace the
stream with yuvdeinterlace, or if you have a high quality source, and
don't need to use the denoiser, with yuvcorrect -T NOT_INTERLACED. Also
set the mpeg2enc interlace-mode (-I) option to 0. This means that there
is no interlacing. We do not really need deinterlacing here because
there is no motion between the fields of the frame. We only need to
unite the two fields into a single progressive frame.
This movie should play back an any device (TV or Monitor) without prob-
lems.
If you have an interlaced source (broadcast) you can encode it as
interlaced stream. Or deinterlace the stream and encode it as progres-
sive stream. If you deinterlace it with yuvdeinterlace, you will lose
details. But if you plan to play the recorded stream on your DVD
player and your TV it would not be wise to perform deinterlacing. If
you only want to play it back on the Monitor (progressive display) the
picture looks better when playing it back if it is deinterlaced. If the
player you use can do deinterlacing it does not matter if your encoded
video has interlaced frames or progressive frames.
If you plan to deinterlace the stream you can only do this with
yuvdeinterlace, and set the mpeg2enc -I 0. If you do not want to dein-
terlace the stream you do not need to set any special option (do not
use yuvdeinterlace and mpeg2enc -I 0)
If you like to pause the stream and look on the still you should dein-
terlace. Because then the image is flicker free when pausing.
If you have a film (progressive) with parts from a broadcast (inter-
laced) mixed together (like in a documentary where some parts from a
speaker are recorded interlaced and other parts are filmed) you have to
choose between good film sequences with average still images or average
looking film sequences with good still images.
For good film with average stills do not deinterlace. For average film
sequences with good stills then deinterlace (using yuvdeinterlace and
mpeg2enc -I 0).
MPEG2 Multiplexing Example
> mplex -f 3 -b 300 -r 4750 -V audio.mp3 video.mp3 -o final.mpg
Now both streams (a mp3 audio and a mpeg2 video) are multiplex into a
single stream (final.mpg). You have to use the -f 3 option to tell
mplex the output format. You also have to add the -b decoder buffers
size with the same value used when encoding the video. -r is that rate
of video + audio +1-2% of mplex information.
The -V option tells that your source for mplexing is a VBR stream. If
you don't use this option mplex creates something like a CBR Stream
with the bitrate you have told it with the -r option. These streams
are usually get BIG.
Creating Video-CD's
VCD is a constrained version of MEPG1 streams. VCD format was defined
by Philips. The goal was to use a single speed CD-drive and other cheap
hardware (not flexible) to have a cheap HW-Player. Because of that
there are some limitations on VCD's. The bitrate for video is 1152kBit
and for audio layer 2 audio 224kBit stereo. You are not allowed to use
the -q option, dynamic GOP sizes and the video buffer is limited to
46kB. The image size is limited to 352x240 for NTSC, an to 352x288 for
PAL.
If you have no VCD (only) player and you plan to use your DVD player
then it is quite possible that the DVD player will be flexible enough
to allow higher bitrates, dynamic GOP sizes, larger video buffer and so
on
VCD Audio creation Example
> lav2wav stream.avi │ mp2enc -V -o sound.mp2
-V force VCD 2.0 compatible output. There the audio samplerate is
fixed to 44.1kHz. And you can choose the audio bitrate for mono audio
to be 64, 96 or 192kBit/sec. If you have stereo audio you can choose
128, 192, 224 or 384kBit/sec. For hardware players, you should stick
to 44.1 224kBps Stereo layer 2 Audio.
VCD Video creation Example
> lav2yuv stream.avi │ yuvscaler -O VCD │ mpeg2enc -f 1 -r 16 -o
video.mpg
For a VCD compatible output the -f 1 sets all options in mpeg2enc as
needed. It seems that many VCD players (Avex for example) are not able
to play MPEG streams that are encoded with a search radius greater than
16 so do not use the -r option to override the default of 16.
> lav2yuv streams.eli │ mpeg2enc -f 1 -4 1 -2 1 -S 630 -B 260 -P -o
video.m1v
Using '-S 630' means that mpeg2enc marks the stream so that mplex gen-
erates a new stream every 630MB. One important thing is the use of the
-B option which specifies the non-video (audio and mplex information)
bitrate. The -B value of 260 should be fine for audio with 224kBit and
mplex information. For further information take a look at the encoding
scripts in the scripts directory. So the multiplexed streams should
easily fit on a CD with 650MB.
The default value (-B) is 700MB for the video. mpeg2enc marks automati-
cally every stream at that size if the -B option is not used to set a
different value. If you have a CD where you can write more data (per-
haps as much as 800MB), you have to set the -S option or otherwise
mpeg2enc will mark the stream at 700 MB, and mplex will split the
stream there. Which is almost certainly not what you want.
VCD Multiplexing Example
> mplex -f 1 sound.mp2 video.mpg -o vcd_out.mpg
The -f 1 option turns on a lot of weird stuff that otherwise has no
place in a respectable multiplexer!
Creating the CD
The multiplexed streams have to be converted to an VCD compatible.
This is done by vcdimager
> vcdimager testvideo.mpg
Creates a videocd.bin, the data file, and a videocd.cue which is used
as control file for cdrdao.
You use cdrdao to burn the image. Cdrdao is yet another fine Source-
forge project which is found at:
Notes
For MPEG-1 encoding a typical (45 minute running time) show or 90 odd
minute movie from an analog broadcast a constant bit-rate of around
1800 kBit/sec should be ideal. The resulting files are around 700M for
45 minutes which fits nicely as a raw XA MODE2 data track on a CD-R.
For pure digital sources (DTV or DVD streams and similar) VCD 1152
works fine.
Note: If you encode VBR MPEG1 (-q) remember the Hardware was probably
not designed to do the playback because it is not in the specifica-
tions. If it works be very happy. I've noticed that it helps when you
have an MPEG1 Stream to tell vcdimager that it is an SVCD. vcdimager
complains (but only with a warning and not a fatal error) but you
should be able to burn it. This could convince the player to use dif-
ferent routines in its firmware and play it back correct, but there is
no guarantee of that.
Storing MPEGs
If you record the data as XA mode 2 tracks you can fit appreciably more
on a CD (at the expense of error correction/detection). You can use
vcdimager to do this and vcdxrip (part of the vcdimager package) to
extract (”rip”) the resulting files. For better Quality there are SVCD
and XVCD and DVD.
Currently SVCD is fully supported with a pre-set format in mplex and
tools to create disks. MPEG streams that can be played by DVD player
hardware and software can readily produced using mpeg2enc/mplex
If your player doesn't support SVCD you may well find it can handle VCD
streams that have much higher than standard bit-rates. Often as much as
2500kBit/sec is possible. The several brands of DVD players can also
play wilding out of spec SVCD and VCD discs. With higher bit-rates and
good quality source material it is worth trying mpeg2enc's -h flag
which produce a stream that is as sharp as the limits of the VCD stan-
dard permits.
However, if your player supports it and you have the patience for the
longer encoding times SVCD is a much better alternative. Using a more
efficient MPEG format SVCD more than doubles VCD's resolution while
typically producing files that are less than twice as big.
Creating SVCD
Super Video CD (SVCD) is an enhancement to Video CD that was developed
by a Chinese government-backed committee of manufacturers and
researchers. The final SVCD spec was announced in September 1998. A
good explanation of the SVCD format from Philips can be found here: .
Record at full TV resolution (means: -d 1 for PAL this is 720x576) The
resolution is for NTSC is 480x480 of PAL 480x576, so you know why you
should record at full size.
SVCD Audio creation Example
> lav2wav stream.avi │ mp2enc -V -e -o sound.mp2
The SVCD specifications permit a much wider choice of audio rates, it
is not necessary to use 224 kBit/sec. Any audio rate between 32 and 384
kBit/sec is permitted. The audio may be VBR (Variable Bit Rate). The -e
enables the CRC error protection for the audio. The CRC has to be
enabled to be SVCD conform. But it seems that most players don't pay
attention to the CRC information. The CRC information need 2 bytes per
Audio frame
The approximate frame length formula for MPEG-1 layer-II is:
(frame length in bytes) = 144 * (byte rate) / (sample rate)
If you have the typical VCD settings the CRC data needs about 0,27% of
the whole data. In the worst case, where you have a MONO 32k Bitrate
stream, the CRC data needs 1,92%.
SVCD Video creation Example
> lav2yuv stream.avi │ yuvscaler -O SVCD │ mpeg2enc -f 4 -q 7 -I 1 -V
200 -o video.m2v
-f 4
sets the options for mpeg2enc to SVCD
-q 7
tell mpeg2enc to generate a variable bitrate stream
-I 1
tell mpeg2enc to assume that the original signal is field interlaced
video where the odd rows of pixels are sampled a half frame interval
after the even ones in each frame. The -I 0 (progressive output (no
field pictures)) option will also work for PAL
You can use lower bitrates, but the SVCD standard limits total bit-rate
(audio and video) to 2788800 Bit/sec. So with 224Kbps audio and over-
head 2550 may already be marginally too tight. Since the SVCD format
permits any audio rate between 32 and 384 kBit/sec you can save a few
bits/sec by using 192k audio (or for non-musical material 160k).
SVCD supports variable bitrate (VBR), because MPEG2 is usually VBR, but
with the top video bitrate limit of 2500kBit/sec. With the -f 4 flag
the encoder also sets dynamic GOP with a low limit of -g 6 and a high
limit of -G 18. This saves a few bits/sec and improves the picture
quality during scene changes. When encoding with -f 4 mpeg2enc ignores
the video bitrate (-b) and search radius (-r) options. If you use -f 5
you have to specify the bitrate and other options to mpeg2enc.
Another possibility for movies in PAL (European style 25 frames/50
fields per sec) video is:
> lav2yuv stream.avi │ yuvscaler -O SVCD │ mpeg2enc -f 4 -I 0 -V 300 -o
video.m2v
Movies are shot on film at 24 frames/sec. For PAL broadcast the film is
simply shown slightly ”too fast” at 25 frame/sec (much to the pain of
people with an absolute pitch sense of pitch). The -I 0 flag turns off
the tedious calculations needed to compensate for field interlacing
giving much faster encoding.
Unfortunately, movies broadcast in NTSC (US style 30 frames/60 fields
sec) video this will produce very poor compression. The ”pulldown” sam-
pling used to produce 60 fields a second from a 24 frame a second movie
means half the frames in an NTSC *are* field interlaced.
Don't forget the -S and -B options mentioned above. You want the stream
to fit on a CD don't you ?
SVCD Multiplexing Example
> mplex -f 4 -b 300 -r 2750 sound.mp2 video.m2v -o svcd_out.mpg
-f 4
tells mplex to mplex a SVCD
-r 2750
is the calculated Audio + Video Bitrate + 1-2% multiplex information
-b 300
is the buffer available on the playback device (the same value as used
for the video encoding (mpeg2enc's -V option).
SVCD Creating the CD
Example:
> vcdimager -t svcd testvideo.mpg
Creates a videocd.bin, the data file, and a videocd.cue which is used
as control file for cdrdao.
Use cdrdao to burn the image as mentioned earlier.
NOTE:If you want to build ”custom” VCD/SVCD you will need to use the
mplex -f 2 and -f 5 switches.
NOTE:The VCD and SVCD stuff may work on your HW player or not. There
are many reports that it works quite well. Don't be worried if it does
not work. Nor am I responsible for unusable CDs. (”coasters”)
Creating DVD's
Everything in this section is very new. So it can change every day.
The limitations I mention here might not exist in the current version.
You need obviously a DVD writer. I own a Ricoh DVD+RW that works, and I
know of a DVD-RAM writer that is able to to burn DVD-R. That disks also
work with a DVD-Player. Which programs you use for burning depends on
the DVD writer drive.
For the creation and writing of the VOB, IFO and BUP files we use
dvdauthor. Aviable from Sourceforge (you might have guessed it) .
DVD Audio creation Example
> lav2wav stream.eli │ mp2enc -o sound.mp2
The sample rate has to be 48kHz. The mp2enc does create by default a
sample rate of 48kHz. If it is not a 48kHz mp2enc will resample the
audio to get the sample rate. If the audio is recorded at 48kHz then
no resampling is needed and toolame can be used for the encoding (it is
faster than mp2enc).
DVD Video creation Example
> lav2yuv stream.eli │ mpeg2enc -f 8 -o video.m2v
-f 8
This sets the options correctly for a MPEG-2 video that is compliant
with the DVD standard. The maximum bitrate is set to 7500kBps and the
video buffer size is set to 230KB. The default quality factor is set to
8. mpeg2enc sets currenty no automatic sequence length as it does for
VCD/SVCD.
The other options to get a low bitrate and high quality stream can also
be used to override the default settings mentioned above. You can also
use yuvdenoise to increase the picture quality if the input data is
noisy (from a VHS tape for example). A typical command will look like
this:
lav2yuv moby.eli │ yuvdenoise │ mpeg2enc -f 8 -q 7 -4 1 -2 1 -P -I 0 -N
-o video_DVD.m2v
DVD Multiplexing Example
> mplex -f 8 sound.mp2 video.m2v -o my_dvdlikestream.mpg
-f 8
Here again we specify that we want to have DVD like MPEG stream. mplex
cannot do all the fancy things allowed for a DVD, but it is close
enough that the HW-DVD players accept it.
-o
there we specify the output filename.
DVD creation Example
This topic will be covered by the documentation of the dvdauthor pro-
gram. For questions please see In general it will work like this:
> makedvd stream1.mpg stream2.mpg ... my_dvdlikestream.mpg
You will get a directory with AUDIO_TS and VIDEO_TS directories. Burn-
ing the data from the disk to a DVD+R/+RW writer would be done like
this:
growisofs -Z /dev/scd2 -dvd-video mydvd/
If you own a DVD+RW/+R drive a good place for more information is:
page. You also need a version of the cdrtools with dvd-video support.
The cdrtools 1.11a27 is known to work but newer versions already exist.
For other writers the commands to write a DVD will be different. You
can get some more information in the dvdauthor package. There is no
guarantee that it will work at all !!!
Creating DIVX Videos
lav2avi.sh
Another way of creating DIVX is the program mencoder which is from the
mplayer project. . For more information about mencoder please read
mencoder/mplayer help and documents. A first and a second pass give at
the end of pass hints for bitrate which can be used for encoding to
specific size (650 MB, 700 MB and 800 MB). The script lav2avi.sh uses
this information if provided (for short streams it is omitted by men-
coder). Look for parameter preferedSize in the script. You can also
specify other parameters used for encoding with encoderParam option in
the script. For a description of the usable parameters take a look in
the mplayer/mencoder manual.
The outputfilename is that name of your input file (first option) but
with the extension avi. If the size of file is less then specified by
preferedSize it's because the source was of very high quality (no
noise) and the specified bitrate was higher than required. You usually
get 700MB for 1.5 hour film at half image size with bitrate around 900
that means for divx good quality (assuming good quality source material
of course).
The script does a 3 step encoding:
1st step - audio encoding
2nd step - first video pass
3rd step - second video pass
The mplayer/mencoder documentation deprecates the use of the 3 pass
encoding method (it can cause A/V sync problems) and recommends the use
of the 2 pass method. The mencoder/mplayer documentation is extensive
and has many helpful hints (and a bitrate calculator in the TOOLS/
directory).
For encoding use the fast ffmpeg (lavc) codec. It gives nice results
together with high good performance. For audio encoding mp3 is used.
For encoding of all parts it uses unix pipes. This mean that you DO NOT
need additional space on your hard drive where all glav manipulations
will be done. For audio encoding the script uses a FIFO queue.
If you want to tweak the script for your own needs, use these hints:
Output of 1st step is file called frameno.avi with encoded audio
2nd step is using frameno.avi and output is text file called
lavc_stats.txt with timing informations
3rd step is using frameno.avi and lavc_stats.txt for encoding the
stream to the output file movie2.avi
If you want change only video bitrate, keep the file frameno.avi com-
ment out the 1st step encoding and repeate 2nd and 3rd step. Dont for-
get to remove the line where the frameno.avi is removed.
Optimizing the stream
Using filters helps to increase the image quality of constant bitrate
(CBR) video streams. With VBR (variable bit rate) video the filesize is
reduced.
Example:
> lav2yuv stream.avi │ yuvmedianfilter │ mpeg2enc -o video.m1v
Here the yuvmedianfilter program is used to improve the image. This
removes some of low frequence noise in the images. It also softens the
image a little. It takes a center pointer and averages the pixels
around it that fall within the specified threshold. It then replaces
the center pixel with this new value. You can also use the -r (radius)
option for an other search radius.
NOTE:a radius greater than the default value of 2 is horrendously slow!
yuvmedianfilter has separate settings for luma and chroma. You can con-
trol the search radius and the trigger threshold independently. If you
use a threshold of 0 then filtering is disabled (-t 0 disables luma
filtering, -T 0 disables chroma filtering).
> lav2yuv stream.avi │ yuvmedianfilter -r 3 -t 4 -T 0 │ mpeg2enc -o
video.m1v
This example uses a search radius of 3 pixels for the luma, a threshold
of 4 (the default is 2), and disables filtering for the chroma compo-
nents. Sometimes, depending on the source material, median filtering
of the chroma can cause a slight color shift towards green. Filtering
on the luma component (disabling the chroma filtering) is the solution
to that problem.
Example:
> lav2yuv stream.avi │ yuvdenoise │ mpeg2enc -o video.m1v
Now we are using yuvdenoise to improve the image. The filter mainly
reduces color and luminance-noise and flickering due to phase errors
but is also effective at removing speckles.
yuvdenoise denoises interlaced if the input is interlaced. You can of
course change the denoiser threshold (-s/g/t). Creating a black border
can lower the bitrate of the encoded stream because pure black areas
compress much better than noise (captures from analog sources such as
VHS and 8mm usually have several lines at the time and bottom that are
very noisy). For this you can use the scaler
yuvdenoise uses a different approach to filter the noise. More infor-
mation about how yuvdenoise works as well as descriptions of its
options are found in the manpage.
If you have a high quality source you should lower the filter to levels
like that: -s 2,2,2 -g 0,255,255 -t 2,2,2. You might also use the
mpeg2enc -h/--keep-hf option. That option tells mpeg2enc to keep as
much high frequency information as possible. Using -h will greatly
increase the bitrate (filesize). If the bitrate is too close to the
maximum (set with -b) the encoder will have to decrease the quality to
avoid exceeding the maximum bitrate.
A builtin filter in mpeg2enc is the -N/--reduce-HF option. This option
is not really filter in the usual sense. Rather it changes how exactly
the high frequency information is encoded. Often the high frequency is
noise. You also have high frequencies on sharp borders or transitions.
The -N option can have values between 0.0 and 2.0 where 0.0 does noth-
ing (disables the high frequency quantizer boost) and 2.0 gives the
maximum quantization boost. The value to use depends on the desired
output quality and filesize. Values of -N less than 0.5 are very sub-
tle while a value of 1.0 will achieve a good balance between bitrate
reduction and output quality. Using -N values above 1.5 will notice-
ably reduce the sharpness of the output picture and are normally used
only for poor quality sources (VHS tapes for example).
Using yuvmedianfilter's capability to only filter the chroma (-T) is
moderately effective at reducing noise in dark scenes without softening
the image during normal (brighter) scenes. Median filtering of the
luma (-t) will produce a lower bitrate but can cause loss of detail
(softening). Chroma only medianfiltering is less agressive and is a
good choice to use in combination with yuvdenoise.
Combining the filters yuvdenoise, yuvmedianfilter and the mpeg2enc -N
option gives a very fine degree of control over the bitrate (filesize).
The reduction (or increase) in the bitrate depends on the source mate-
rial and the exact encoding/filter options used. So we can give no
exact numbers how much each option and combination will reduce the
filesize, only guidelines.
Usually you should use the -N option in a range from 0.5 to 1.5. Below
0.5 it does not reduce the bitrate very much (but does preserve sharp-
ness). At 1.5 and higher you will notice a softening in the video and
possibly artifacts (halo/ringing) around edges of objects (text/subti-
tles especially). If you combine the filters you should use yuvdenoise
and maybe afterwards yuvmedianfilter. Maybe yuvmedianfilter even after
scaling. Having yuvmedianfilter in the chain does not reduce the
bitrate that much. Often the use of yuvdenoise is enough. The yuvme-
dianfilter helps much if you have low quality sources, and not that
much if you already have a rather good quality. When you combine the
filter and option you will very likely reduce the filesize to about the
half of the filesize without using the options and programs.
In general aggressive filtering will produce smaller files (lower
bitrate) but reduce the quality (details) of the picture. Less aggres-
sive filtering/processing will preserve more detail but result in
larger files.
Example:
> lav2yuv stream.avi │ yuvkineco -F 1 │ mpeg2enc -o video.m1v
yuvkineco is used for NTSC sources. It does the conversation from
30000.0/1001.0 (about 29.97) fps to 24000.0/1001.0 (about 23.976) fps,
you can call it ”reverse 2-3 pulldown” more info about this in the
README.2-3pulldown. yuvkineco does only remove NTSC specific problems.
If you want to improve the image you should also use yuvdenoise:
> lav2yuv stream.avi │ yuvkineco │ yuvdenoise │ mpeg2enc -o video.m1v
Example
> lav2yuv stream.avi │ yuvycsnoise │ mpeg2enc -o video.m1v
yuvycsnoise is also used for NTSC and is specialized for NTSC Y/C sepa-
ration noise. If video capture hardware has only a poor Y/C separator
then at vertical stripes (especially red/blue) noises appear which seem
checker flag and bright/dark invert per 1 frame. yuvycsnoise reduces
noises of this type. You can also use different thresholds for
luma/chroma and the optimizing method. This filter is not needed with
working with DV (Digital Video) data.
yuvycsnoise works only correct when we have NTSC with:
full height (480 lines)
full motion captured (29.97 fps)
captured with poor Y/C separator hardware
For more information about the yuvkineco and yuvycsnoise read the
README in the yuvfilters directory.
If you want to experiment to determine the optimal settings for the
denoiser, scaler and so on replace the mpeg2enc with yuvplay. yuvplay
plays back the yuv frames so you can see if the options you have chosen
are making the thing better or worse.
A command would look like this:
> lav2yuv stream.eli │ yuvdenoise -options │ yuvscaler -options │
yuvplay
If you are looking for a hardware device that can make the video look
better before you record it we currently know about two firms that pro-
duce such boxes.
One produced by SIMA: , that device will work with NTSC. And a one
other produced by ELV (german distributor):
there you find in the SHOP area, a section where you can take a look at
their Video - Audio devices. Most of the ELV devices work only with
PAL.
If you want to know how much each tool lowers the average bitrate. You
can use this table to see what you can expect if you have a full size
video and want to create a DVD with a qality factor of 5 and the
allowed maximal bitrate of 8500kb/sec.
no denoising : 8300 kb/s (mostly hitting the upper bound)
yuvenoise : 7700 kb/s
mpeg2enc --reduce-hf : 7400 kb/s
yuvdenoise + yuvmedianfilter : 6000 kb/s
yuvdenoise + mpeg2enc --reduce-hf : 4900 kb/s
all of the above : 3600 kb/s
While -N│--reduce-hf or yuvdenoise alone is only a modest improvement,
together they reduce the bitrate substantially. There is not really
much visible difference between using yuvdenoise alone and yuvdenoise
with mpeg2enc --reduce-hf. The usefull values are between 0.0 and 1.5.
Where you can say that the higher the quality factor you want, the less
this option improves. At a quality factor 4 you save using -N 1.0 about
1%. If you want a quality factor of 9 and use the -N 1.0 you might save
up to 40%. But you might save less, that depends on the video you
encode!!!
If you ask yourself why not alyways use all of the above filters?
Hmmm, hard question. The image softens, and the encoding time
increases. Each filter needs about the same amount of time as mpeg2enc
needs for encoding the video.
If you have very high quality material and want to keep every detail
you should try to use the mpeg2enc --keep-hf│-h on the other hand
Note: The bitrate reduction you have depends on the material and on the
noise of the images.
A other interresting mpeg2enc option is the -E│--unit-coeff-elim
option. This option is disabled by default. If you enable it, a special
"unit coefficient elimination" algorithm, is applied to the encoded
picture blocks. Basically this proceedure forces blocks of a type
that do not carry much information (but use many bits to encode) to be
skipped. A negative value examines the base (DC) as well as the AC
coefficients. A positive value means that only texture (AC)
coefficients are examined and possibly zeroed. The recommended values
lies between -20 and +20. You usually can expect that you have a 5%
decreased filesize. The amount the bitrate is reduced can vary consid-
erably, the range spans from not really noticable up to 20%.
If you think a other quantization matrice will help use the -K│--cus-
tom-quant-matrices option. You can try out your own quanitsation
matrice or use another builtin than the default. You can choose
between kvcd, tmpgenc, hi-res, and your own. Using -K usually makes the
file smaller except the hi-res option (that makes files considerably
larger). Exact guidelines are hard to give, sometime a other quanitsa-
tion matrix saves almost nothing, and the next time up to 20%. More
than 20% is very unlikely, 10-15% at a moderate qualityfactor (-q 8-10)
are likely. The higher the qualiy the less it saves, at a quality fac-
tor of 4-6 the reduction in bitrate may only be 5%
One thing to keep in mind is that the unit coefficient elimination and
the quantization matrix option are decreasing the bitrate while main-
taining the same visual quality. At this point you can chose to use
the smaller file to increase the amount of video that will fit on the
disc media or you could chose to increase the quality even more by low-
ering the -q value by 1 and make a larger (but higher quality) file.
Scaling and offset correction
The basic scaling is described in the Converting video section
The scaling, takes a part of the picture, and scales it to a larger or
smaler size. The scaling is done by yuvscaler:
lav2yuv test.eli │ yuvscaler -I USE_400x400+50+100 │ yuvplay
Here we only take part of the picture and scale it up to the size of
the original frame. But yuvscaler also changes the pixel aspect ratio.
That means when you look at the stream using yuvplay it looks like a
square in our example. After scaling, if the sample (pixel) aspect
ratio were not changed, the video would not display with the proper
aspect ratio. Yuvscaler compensates by adjusting the sample aspect
ratio. If you have a interlaced video, the height and HeightOffset
have to be a multiple by 4 if the video is interlaced. Else the values
(width, height, widthoffset, heightoffset) have to be a multiple of 2.
A problem that cannot be solved easily with scaling is when the picture
is not centered horizontal. On one side you have no black pixels and on
the other you have 30 for example. Scaling is here is the wrong solu-
tion. y4mshift is the perfect solution because it can shift the image
to the left or right.
lav2yuv test.eli │ y4mshift -n 20 │ mpeg2enc -f 3 -b 4000 -q 10 -o
video.m2v
That will shift the image 20 pixels to the right. If you use a negative
the image is shift to the left. You have to use a even number. The
inserted pixels are set to black.
Some might wonder why the image is not centered and there is a black
border around the image when you view what you have recorded. The rea-
son for the black border is the TV BT = Catode Ray Tube) and a really
interresting storry about how the TV standart was definden. But tha
topic is described in other books.
The TV does not show the full picture. A part of the picture is not
shown because the TV sets overscan (sometimes as much as 10% but more
common today is 5%). But when you capture the video with a card you
see the whole image including the border that TVs lose due to overscan-
ning. A horizontal offset is usually not a problem of the capture
card. It is a problem when the film is broadcast and not well synchro-
nized with the image. This means that the scan of the source not
exactly synchronized with the carrier signal, you wont see that on TV.
Frame rate conversion
Ever needed to convert the framerate from PAL to NTSC or the other
direction around ? Or something much simpler like converting the fram-
erate from 24FPS to 24000:1001 for conversation from a film frame rate
to a valid NTSC frame rate.
Than yuvfps is your program. It can lower the framerate by dropping
frames, or create a higher framerate by replicating frames. If you have
a wrong framerate in the header you can only change the header of the
YUV stream and not modify the stream.
Because the frames are only replicated (copied) you should denoise
first and then change the framerate and scale at als last step. If you
have a interlaced source you should also deinterlace before changeing
the framerate. If you create a higher frame rate it is very likely that
you will have weird flickers when you play it back. If you convert PAL
to NTSC (30000:1001 FPS about 29,97 FPS) the frame rate will lower by
about the factor 480/576 (NTSC lines / PAL lines). If you lower the
frame rate from PAL to NTSC (at 24000:1001) or NTSC FILM (24FPS) the
bitrate will be about (480 Lines * 24 FPS) / (576 Lines * 25FPS). If
you change the frame rate before denoising the yuvdenoise will have
problems finding the noise across the frames, so the needed bandwith
will slightly increase.
Example
> lav2yuv video.eli │ yuvfps -r 30000:1001 │ yuvscaler -O SVCD │
mpeg2enc -f 4 -o video_ntsc_svcd.m2v
This is a example to convert the source video to a NTSC video running
at 30000:1001 FPS (or about 29,97FPS) at SVCD size.
Example
> lav2yuv video.eli │ yuvdenoise │ yuvfps -r 24000:1001 │ yuvscaler -O
SIZE_720x480 │ mpeg2enc -f 3 -b 4000 -q 7 -o video_ntsc.m2v
This example shows how you should use the tools. Denoise first and than
change the framerate and in the last step change the image size.
It can happen that yuvscaler or mpeg2enc do not detect the TV norm cor-
rect. If that happens you have to add the norm option -n n/p/s to the
program that chooses the wrong norm.
If you know that the header tells the wrong framerate, you can simply
change the framerate of the yuv header this way:
> lav2yuv video.eli │ yuvfps -r 25:1 -c │ mpeg2enc -f 3 -b 4000 -q 7 -o
video_pal.m2v
You need the -c option. To tell yuvfps that it only should change the
header of the stream. With the -r 25:1 you tell yuvfps the frame rate
it should write into the header. In your example the PAL frame rate of
25 FPS. You always have to use the fractional form.
If you know that the header is wrong, and you need a different output
bitrate you can do this in a single step:
> lav2yuv video.eli │ yuvfps -s 24:1 -r 25:1 │ mpeg2enc -o
video.m1vTranscoding of existing MPEG-2
For transcoding existing MPEG-2 streams from digital TV cards or DVD a
lower data-rate than for broadcast will give good results. Standard
VCD 1152 kbps typically works just fine for MPEG1. The difference is in
the Signal/Noise ratio of the original. The noise in the analog stuff
makes it much harder to compress.
One other very good guide that helps you transcoding videos can be
found at:
You will also need to manually adjust the audio delay offset relative
to video when multiplexing. Very often around 150ms delay seems to do
the trick.
You have to download the ac3dec and mpeg2dec packages. You can find
them at mjpeg homepage ( ). You also need sox and toolame.
In the scripts directory there is a mpegtranscode script that does most
of the work.
So transcoding looks like this:
> mjpegtranscode -V -o vcd_stream mpeg2src.mpg
-V
set's the options so that a VCD compatible stream is generated
-o vcd_stream
a vcd_stream.m1v (video) and vcd_stream.mp2 (audio) is created
mpeg2src.mpg
specifies the source stream
The script prints also something like this:
> SYNC 234 mSec
You will need to adjust the audio/video startup delays when multiplex-
ing to ensure audio and video are synchronized. The exact delay (in
milliseconds) that you need to pass to mplex to synchronize audio and
video using the ”-v”" is printed by the extract_ac3 tool labeled ”SYNC”
when run with the ”s” flag. This is the value th mjpegtranscode script
prints out after the SYNC word.
Then you need to multiplex them like this:
> mplex -f 1 -O 234 vcd_stream.mp2 vcd_stream.m1v -o lowrate.mpg
-f 1
Mux format is set to VCD
-O 234
Video timestamp offset in mSec, generated by the mjpegtranscoding
script, there negative values are allowed
vcd_stream.mp2 & vcd_stream.m1v
generated files by the script
lowrate.mpg
the VCD compatible output stream
Here we have a SVCD (MPEG-2 video) example:
> mjpegtranscode -S -o svcd_stream mpeg2src.mpg
You have to multiplex it with:
> mplex -f 4 -O 234 svcd_stream.mp2 svcd_stream.m2v -o lowrate.mpg
Problem: There is sometimes a problem with NTSC and VCD playback
because movies may be recoded with 3:2 pulldown NTSC with 60
fields/sec. mpeg2dec is designed for playback on computers and gener-
ates the original 24frames/sec bitrate. If you encode the video now
30frames/sec video is created. This video is now much too short for the
encoded audio.
The transcoding can be made to work but it must be done manually:
> cat mpeg2src.mpg │ mpeg2dec -s -o YUVs │ mpeg2enc -I 0 -f 4 -q 9 -V
230 -p -P -o svcd_stream.m2v
The -p tells mpeg2enc to generate header flags for 3:2 pull down of
24fps movie. It may also work if you do not add the -p flag. You do
not need the -p flag when transcoding to VCD format because it is not
supported in mpeg1.
If you want to do every step on your own it will look something like this
Extracting Audio:
> cat test2.mpg │ extract_ac3 - -s │ ac3dec -o wav -p sound.wav
2>/dev/null
One of the first lines showed contains the label ”SYNC” you have to use
this time later when multiplexing. The 2>/dev/null redirects the output
of ac3dec to /dev/null. In the next step you generate the mpeg audio
file:
> cat sound.wav │ mp2enc -V -v 2 -o audio.mp2
-V
forces VCD format, the sampling rate is converted to 44.1kHz from 48kHz
-v 2
unnecessary but if you use it mp2enc tells you how many seconds of the
audio file are already encoded.
-o
Specifies the output file.
cat test2.mpg │ extract_ac3 - -s │ ac3dec -o wav │ sox -t wav
/dev/stdin -t wav -r 44100 /dev/stdout │ toolame -p 2 -b 224 /dev/stdin
audio.mp2
One of the first lines again output contains the label ”SYNC”. You
have to use this time (referred to as "SYNC_value" below) when doing
the multiplexing.
For VCD creation use:
> cat test2.mpg ” mpeg2dec -s -o YUVh ” mpeg2enc -s -o video_vcd.m1v
mpeg2dec:
-s
tells mpeg2dec to use program stream demultiplexer
-o YUVh
the output size of the extracted frames.
There are other output modes, try ”mpeg2dec --help” but the most impor-
tant here are:
YUV
is the full image size, unscaled
YUVs
is SVCD size, it can only scale down to 2/3 of the original size
YUVh
is VCD size, or about the half of the original size
Mplex with:
> mplex -f 1 -O SYNC_value audio.mp2 video_vcd.m1v -o vcd_stream.mpg
-f 1
generates an VCD stream
-O SYNC_value
the value mentioned above
For SVCD creation use:
> cat test2.mpg │ mpeg2dec -s -o YUVs │ mpeg2enc -f 4 -q 9 -V 230 -o
video_svcd.mpg
-q 9
Quality factor for the stream (VBR stream) (default q: 12)
-V 230
Target video buffer size in KB
-o
Output file
Mplex with:
> mplex -f 4 -b 230 audio.mp2 video_svcd -o svcd_stream.mpg
-f 4
generate an SVCD stream
-b 200
Specify the video buffer size by the playback device.
For other video output formats this might work:
> cat test2.mpg │ mpeg2dec -s -o YUV │ yuvscaler -O SIZE_320x200 -O
NOT_INTERLACED │ mpeg2enc -o strange_video.m1v
If you want to edit mpeg streams, this also works, but in a slightly
different way. For demultiplexing you can use bbdmux, from the bbtools
package. Splits out either video or audio very cleanly. You can't get
it any more from the homepage from Brent Beyler, it can still be found
when you search for it using that keywords ” bbtools linux -suse
-blackbox”. Currenty it can be found at:
First run:
> bbdmux myvideo.mpg
You should get something like this:
Found stream id 0xE0 = Video Stream 0
Found stream id 0xC0 = MPEG Audio Stream 0
Found stream id 0xBE = Padding Stream
Extract audio with:
> bbdmux myvideo.mpg 0xC0 audio.mp1
Convert it to wav:
> mpg123 -w audio.wav audio.m1v
Extract video with:
> bbdmux myvideo.mpg 0xE0 video.m1v
Converting video to an mjpeg avi stream:
> cat video.m1v │ mpeg2dec -o YUV │ yuv2lav -f a -o test.avi
Then adding the sound to the avi:
> lavaddwav test.avi audio.wav final.avi
If the source video has already the size of the target video use -o
YUV. Using YUVh makes the video the half size! The rest can be done
just like editing and encoding other streams. If you have videos with
ac3 sound you only have to adapt the commands above.
Extracting Audio:
> cat test2.mpg │ extract_ac3 - -s │ ac3dec -o wav 2>dev/null
>sound.wav
Extract video:
> cat test2.mpg │ mpeg2dec -s -o YUVh │ yuv2lav -f a -q 85 -o test.avi
Adding the sound:
> lavaddwav test.avi sound.wav fullvideo.avi
NOTE:You need much disk space. 1GB of video has a size of about 2GB at
SVCD format and of course disk space is needed for some temp files.
Converting the video to mjpeg also takes some time. On my Athlon 500 I
never get more than 6-7 Frames a second. You loose quality each time
you convert a stream into an other format! Trading Quality/Speed
If absolute quality is your objective a modest improvement can be
achieved using the -4 and -2 flags. These control how ruthlessly
mpeg2enc discards bad looking matches between sections of adjacent
frames during the early stages of the search when it is working with
4*4 and 2*2 clusters of pixels rather than individual pixels. Setting
-4 1 -2 1 maximizes quality. -4 4 -2 4 maximizes speed. Note that
because the statistical criteria mpeg2enc uses for discarding bad look-
ing matches are usually fairly reliable the increase/decrease in qual-
ity is modest (but noticeable).
Reducing the radius of the search for matching sections of images also
increases speed. However due to the way the search algorithm works the
search radius is in effect rounded to the nearest multiple of 8. Fur-
thermore, on modern CPU's the speed gained by reducing the radius below
16 is not large enough to make the marked quality reduction worthwhile
for most applications.
Creating streams to be played from disk using Software players
Usually MPEG player software is much more flexible than the hardware
built into DVD and VCD players. This flexibility allows for signifi-
cantly better compression to be achieved for the same quality. The
trick is to generate video streams that use big video buffers (500KB or
more) and variable bitrate encoding (the -f, -q flag to mpeg2enc).
Software players will often also correctly play back the more efficient
MPEG layer 3 (yes, ”MP3” audio format. A good MP3 encoder like lame
will produce results comparable to layer 2 at 224Kbps at 128Kbps or
160Kbps.SMP and distributed Encoding
The degree to which mpeg2enc tries to split work between concurrently
executing threads is controlled by the -M or --multi-thread [0..32]
option. This optimizes mpeg2enc for the specified number of CPUs. By
default (-M 1), mpeg2enc runs with just a little multi-threading: read-
ing of frames happens concurrently with compression. This is done to
allow encoding pipelines that are split across several machines (see
below) to work efficiently without the need for special buffering pro-
grams. If you are encoding on a single-CPU machine where RAM is tight
you may find turning off multithreading altogether by setting -M 0
works slightly more efficiently.
For SMP machines with two ore more processors you can speed up mpeg2enc
by setting the number of concurrently executing encoding threads's you
wish to utilize (e.g. -M 2). Setting -M 2 or -M 3 on a 2-way machine
should allow you to speed up encoding by around 80%. Values above 3
are accepted but have very little effect even on 4 cpu systems.
If you have a real fast SMP machine (currently 1.Aug.03) like a dual
Athlon MP 2600 or something similar the -M 2 and the filtering might
not keep both (or more) CPU's busy. The use of the buffer or bfr pro-
gram with a 10-20MB buffer helps to keep both CPUs busy.
Obviously if your encoding pipeline contains several filtering stages
it is likely that you can keep two or more CPU's busy simultaneously
even without using -M. Denoising using yuvdenoise or yuvmedianfilter is
particular demanding and uses almost as much processing power as MPEG
encoding.
It you more than one computer you can also split the encoding pipeline
between computers using the standard 'rsh' or 'rcmd' remote shell exe-
cution commands. For example, if you have two computers:
> rsh machine1 lav2yuv ”mycapture.eli │ yuvscaler -O SVCD │ yuvdenoise”
│ mpeg2enc -f 4 -o mycapture.m2vi
Here the computer where you execute the command is doing the MPEG
encoding and ”machine1” is the machine that is decoding scaling and
denoising the captured video.
Obviously, for this to work ”machine1” has to be able to access the
video and the computer where the command is executed has to have space
for the encoded video. In practice, it is usually well worth setting up
network file-storage using ”NFS” or other packages if you are going to
do stuff like this. If you have three computers you can take this a
stage further, one computer could do the decoding and scaling, the next
could do denoising and the third could do MPEG encoding:
> rsh machine1 ”lav2yuv mycapture.eli │ yuvscaler -O SVCD” │ yuvdenoise
│ rsh machine3 mpeg2enc -f 4 -o mycapture.m2v
NOTE:How the remote command executions are set up so that the data is
sent direct from the machine that produces it to the machine that con-
sumes it.
In practice for this to be worthwhile the network you are using must be
fast enough to avoid becoming a bottleneck. For Pentium-III class
machines or above you will need a 100Mbps Ethernet.
For really fast machines a switched 100MBps Ethernet (or better!) may
be needed.Setting up the rshd (”Remote Shell Daemon” needed for rsh to
do its work and configuring ”rsh” is beyond the scope of this document |
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