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• Where is the documentation for the Mjpeg codec used in mencoder, VLC and FFMpeg ?

  18 août 2011, par Sugrue

  Mencoder has a lovely option for converting a mjpeg file into an avi file with an 'MJPG' codec that plays in VLC.

  The command line to do this is:

  mencoder filename.mjpeg -oac copy -ovc copy -o outputfile.avi -speed 0.3

  where 0.3 is the ratio of the desired play framerate to the default 25 fps. All this does is make a copy of the mjpeg file, put an avi header on top and at the end, what seems to be an index of the frame positions in the file.

  I want to replicate this in my own code, but I can't find documentation anywhere. What is the exact format of the index section? The header has extra filler bytes in it for some reason - whats this about?

  Anyone know where I can find documentation? Both mencoder and vlc seem to have this codec built in.

• Ffmpeg compilation fails due to undefined symbol _x264_encoder_open_112 for architecture x86_64

  18 août 2011, par Saptarshi Biswas

  I am compiling ffmpeg on Snow Leopard from source. Using Macport is not an option since I have some custom modification in ffmpeg. The make commands are:

  $ ./configure --enable-gpl --enable-libmp3lame --enable-static \
              --disable-shared --enable-libx264 --enable-pthreads \
              --disable-doc --enable-avfilter
  $ make
  

  The error:

  CC  ffplay.o
  ffplay.c: In function ‘SDL_main’:
  ffplay.c:3157: warning: assignment discards qualifiers from pointer target type
  LD  ffplay_g
  Undefined symbols for architecture x86_64:
    "_x264_encoder_open_112", referenced from:
        _X264_init in libavcodec.a(libx264.o)
  ld: symbol(s) not found for architecture x86_64
  collect2: ld returned 1 exit status
  make: *** [ffplay_g] Error 1
  

  ---

  I have compiled libx264 from source, which went fine.

  $ cd x264-snapshot-20101228-2245; ./configure && make && sudo make install
  

  ... and it contains the symbol "_x264_encoder_open_112"

  $ nm ./libx264.a | grep _x264_encoder_open_112
  0000000000003ef0 T _x264_encoder_open_112
  000000000000d7b0 S _x264_encoder_open_112.eh
  

  What might be going wrong?