mjpegtools.1

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recording at full resolution as you need to reduce to -d 2 resolution
later anyway.

.PP
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

.PP

.SH Some information about the typical lavrec output while recording


.PP
0.06.14:22 int: 00040 lst:0 ins:0 del:0 ae:0 td1=0.014 td2=0.029

.PP
The first part shows the time lavrec is recording.
\fBint:\fP the interval between two frames. \fBlst:\fP the number of
lost frames. \fBins and del:\fP are the number of frames inserted and
deleted for sync correction. \fBae:\fP number of audio errors.
\fBtd1 and td2\fP are the audio/video time-difference.

.PP
.nr ll +1
.nr t\n(ll 0
.if \n(ll>1 .RS
.nr bi 1
.PP

\fB(int) frame interval\fP 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
.nr bi 1
.PP

\fB(lst) lost frames\fP 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.
.nr bi 1
.PP

\fB(ins, del) inserted OR deleted frames\fP 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.
.nr bi 1
.PP

\fB(ae) audio errors\fP are never good. Should be 0
.nr bi 1
.PP

\fB(td1, td2) time difference\fPis always floating around 0, unless
sync correction is disabled (--synchronization!=2, 2 is default).
.if \n(ll>1 .RE
.nr ll -1

.PP
.SH Notes about \(rqinterlace field order - what can go wrong and how to fix it\(rq


.PP
Firstly, what does it mean for interlace field order to be wrong?

.PP
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).

.PP

.PP
There are three bad things that can happen with fields


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.nr ll +1
.nr el +1
.nr t\n(ll 1
.nr e\n(el 0 1
.af e\n(el \*(f\n(el
.if \n(ll>1 .RS
.nr bi 1
.PP

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.
.nr bi 1
.PP

The two fields can simply be swapped somehow so that top gets treat
as bottom and bottom treat as top. Juddering and \(rqslicing\(rq is the
result. This occasionally seems to happen due to hardware glitches in the
capture card.
.nr bi 1
.PP

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 \(rqjuddering\(rq effects are the results.
.if \n(ll>1 .RE
.nr el -1
.nr ll -1

.PP

.PP
How can I recognize if I have one of these Problems ? 


.PP
.nr ll +1
.nr el +1
.nr t\n(ll 1
.nr e\n(el 0 1
.af e\n(el \*(f\n(el
.if \n(ll>1 .RS
.nr bi 1
.PP
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! 
.nr bi 1
.PP
The two fields can simply be swapped somehow so that top gets treat
as bottom and bottom treat as top. Juddering and \(rqslicing\(rq is
the result. This occasionally seems to happen due to hardware glitches in
the capture card. That problem lookes like that:


.PP
Interlacing problem

.PP

.PP
.nr bi 1
.PP
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 
\(rqjuddering\(rq effects are the result.
.if \n(ll>1 .RE
.nr el -1
.nr ll -1

.PP
If you use glav or lavplay be sure that you also use the \fB-F/--flicker\fP
option. This disables some things that make the picture look better.

.PP
If you want to look at the video you can also use yuvplay:

.PP
\fB> lav2yuv \(br ... \(br yuvplay\fP

.PP
If there is a field order problem you should see it with yuvplay.

.PP

.PP
How can you fix it? 


.PP
.nr ll +1
.nr el +1
.nr t\n(ll 1
.nr e\n(el 0 1
.af e\n(el \*(f\n(el
.if \n(ll>1 .RS
.nr bi 1
.PP
To fix this one the fields need to be \(rqshifted\(rq through
the frames. Use yuvcorrect's \fB-T BOTT_FORWARD/TOP_FORWARD\fP 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: \fB> lav2yuv -v 2 the_mjpeg_file > /dev/null\fP 
Or re-record exchanging \fB-f a\fP for \fB-F A\fP or vice-versa. 
.nr bi 1
.PP
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
\fB-T LINE_SWITCH\fP\&. 
.nr bi 1
.PP
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
\(rqindirectly\(rq by telling mpeg2enc when encoding to \fBreverse the
flag (-z b\(brt)\fP that tells the decoder which field order to use. 
.if \n(ll>1 .RE
.nr el -1
.nr ll -1

.PP

.PP
\fBIn 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:\fP

.PP
.DS
.sp 
.ft RR
.nf
> mkdir pnm 
> lav2yuv -f 40 video.avi \(br y4mtoppm \(br pnmsplit - pnm/image%d.pnm 
> rm pnm/image?.pnm 
> cd pnm 
> xv 
.DE
.fi 
.ec
.ft P
.sp

.PP
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 numbering. Without
a leading zero in the number, the files will be sorted in the wrong order,
leading to confusing playback.

.PP
Use your favorite graphic program (xv for example) to view the pictures. 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.

.PP
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 , ....

.PP
To fix this problem you have to use yuvcorrect's \fB-T BOTT_FORWARD or
TOP_FORWARD\fP\&. 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 \fB-M LINE_SWITCH\fP, or use the mpeg2enc \fB-z (b\(brt)\fP option.

.PP
To see if you guessed correctly, extract the frames again, reordering them
using yuvcorrect:

.PP
\fB> lav2yuv -f 40 video.avi \(br yuvcorrect -T OPTION \(br y4mtoppm \(br pnmsplit - pnm/image%d.pnm \fP

.PP
Where \(rqOPTION\(rq is what you think it will corrects the problem.
This is for material converted from film. Material produced directly for TV
is addressed below.

.PP

.PP
Hey, what about NTSC movies ?


.PP
Movies are broadcast in NTSC using \(rq3:2\(rq 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. 

.PP
If you have an interlaced source like a TV camera you have a frame consists
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.

.PP
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.

.PP
You can only have this problems if you record at full size !!! 

.PP
Creating videos from other sources


.PP
Here are some hints and descriptions of how to create the videos from other
sources like images and other video types.

.PP
You might also be interested in taking a look at the
\fBTranscoding of existing MPEG-2\fP section.

.PP

.PP
.SH Creating videos from images


.PP
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 anything else.

.PP
Saving an yuv stream can be done like this:

.PP
\fB> jpeg2yuv -f 25 -I p -j image%05d.jpg > result.yuv\fP

.PP
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

.PP
If you want to encode a mpeg video directly from jpeg images without saving
a separate video file type:

.PP
\fB> jpeg2yuv -f 25 -I p -j image%05d.jpg \(br mpeg2enc -o mpegfile.m1v\fP

.PP
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.

.PP
You can also use yuvscaler between jpeg2yuv and mpeg2enc. If you want to
create a SVCD from your source images:

.PP
\fB> jpeg2yuv -f 25 -I p -j image%05d.jpg \(br yuvscaler -O SVCD
\(br  mpeg2enc -f 4 -o video.m2v\fP

.PP
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 number. For
example, if your first image is image01.jpg rather than image00.jpg, and 
you only want 60 images to be processed type:

.PP
\fB>jpeg2yuv -b 1 -f 25 -I p -n 60 -j image*.jpg \(br yuv2lav -o stream_without_sound.avi\fP

.PP
Adding the sound to the stream then:

.PP
\fB> lavaddwav stream_without_sound.avi sound.wav stream_with_sound.avi\fP

.PP
For ppm input there is the ppmtoy4m util. There is a manpage for ppmtoy4m that
should be consulted for additional information.

.PP
So to create a mpeg video try this:

.PP
\fB>cat *.ppm \(br ppmtoy4m -o 75 -n 60 -F 25:1 \(br mpeg2enc -o output.m1v\fP

.PP
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.

.PP
Other picture formats can also be used if there is a converter to ppm.

.PP
\fB>ls *.tga \(br xargs -n1 tgatoppm \(br ppmtoy4m \(br yuvplay\fP

.PP
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 single image at a time.

.PP
If you want to use the ImageMagick 'convert' tool (a Swiss Army Knife) try:

.PP
\fB>convert *.gif ppm:- \(br ppmtoy4m \(br yuvplay\fP

.PP
That means take all '.jpg' images in directory, convert to PPM format,
and pipe to stdout, then ppmtoy4m processes them ....

.PP
.SH Decoding streams with mplayer 


.PP
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

.PP
\fB>mkfifo stream.yuv\fP

.PP
\fB>mplayer -nosound -noframedrop -vo yuv4mpeg anyfile.mpg &\fP

.PP
\fB>cat stream.yuv \(br yuv2lav -o mjpeg_wo.avi\fP

.PP
\fB>mplayer -vo null -ao pcm -aofile anyfile.wav anyfile.mpg\fP

.PP
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 \fBlavaddwav\fP and edit the file and encode it.

.PP
You can also use instead of yuv2lav, mpeg2enc or any other tool from the 
mjpeg tools so your command might also look like that:

.PP
\fB> cat stream.yuv \(br yuvdenoise \(br yuvscaler -O SVCD \(br mpeg2enc -f 4 -o video_svcd.m2v\fP

.PP
And cat the wav file into \fBmp2enc\fP to encode it to MP2 audio. The 
\fB-vo yuv4mpeg\fP option works well with other input types mentioned in
the mplayer documentation. 
.SH Decoding MPEG2 streams with mpeg2dec