mjpeg_howto.txt

Motion JPEG编解码器源代码

  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 ....


  4.2.  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.


  4.3.  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
  program.  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.


  4.4.  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: http://forum.lucike.info/

  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.

  5.  Checking if recording was successful

  You can use lavplay or glav. IMPORTANT: NEVER try to run xawtv and
  lavplay 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
  generated 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: http://ronald.bitfreak.net


  6.  Edit the video


  6.1.  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.



  6.2.  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.



  6.3.  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
  format.

  Another way to split the sound is:

  > lav2wav editlist.eli >sound.wav



  6.4.  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.
  6.5.  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
  transist.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