У меня есть файл mp4, и я хочу конвертировать в mpg с аудио кодеком AC3.

Я старался:

                  ffmpeg -i input.mp4  -c:a ac3 output.mpg 

вывод команды:

      bash$ ffmpeg -i input.mp4 -c:a ac3  output.mpg
      ffmpeg version 2.1.3 Copyright (c) 2000-2013 the FFmpeg developers
        built on Jan 15 2014 20:53:51 with gcc 4.8.2 (GCC) 20131219 (prerelease)
        configuration: --prefix=/usr --disable-debug --disable-static --enable-avresample --enable-dxva2 --enable-fontconfig --enable-gnutls --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libv4l2 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-pic --enable-postproc --enable-runtime-cpudetect --enable-shared --enable-swresample --enable-vdpau --enable-version3 --enable-x11grab
        libavutil      52. 48.101 / 52. 48.101
        libavcodec     55. 39.101 / 55. 39.101
        libavformat    55. 19.104 / 55. 19.104
        libavdevice    55.  5.100 / 55.  5.100
        libavfilter     3. 90.100 /  3. 90.100
        libavresample   1.  1.  0 /  1.  1.  0
        libswscale      2.  5.101 /  2.  5.101
        libswresample   0. 17.104 /  0. 17.104
        libpostproc    52.  3.100 / 52.  3.100
      Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './input.mp4':
        Metadata:
          major_brand     : isom
          minor_version   : 512
          compatible_brands: isomiso2avc1mp41
          creation_time   : 1970-01-01 00:00:00
          encoder         : Lavf52.43.0
        Duration: 00:08:41.86, start: 0.000000, bitrate: 437 kb/s
          Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 512x272 [SAR 215:213 DAR 6880:3621], 358 kb/s, SAR 129:128 DAR 129:68, 23.98 fps, 23.98 tbr, 2997 tbn, 47.95 tbc (default)
          Metadata:
        creation_time   : 1970-01-01 00:00:00
        handler_name    : VideoHandler
          Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 22050 Hz, stereo, fltp, 75 kb/s (default)
          Metadata:
        creation_time   : 1970-01-01 00:00:00
        handler_name    : SoundHandler
      [mpeg @ 0x9361f60] VBV buffer size not set, muxing may fail
      Output #0, mpeg, to './output.mpg':
        Metadata:
          major_brand     : isom
          minor_version   : 512
          compatible_brands: isomiso2avc1mp41
          encoder         : Lavf55.19.104
          Stream #0:0(und): Video: mpeg1video, yuv420p, 512x272 [SAR 129:128 DAR 129:68], q=2-31, 200 kb/s, 90k tbn, 23.98 tbc (default)
          Metadata:
        creation_time   : 1970-01-01 00:00:00
        handler_name    : VideoHandler
          Stream #0:1(und): Audio: ac3, 22050 Hz, stereo, fltp, 192 kb/s (default)
          Metadata:
        creation_time   : 1970-01-01 00:00:00
        handler_name    : SoundHandler
      Stream mapping:
        Stream #0:0 -> #0:0 (h264 -> mpeg1video)
        Stream #0:1 -> #0:1 (aac -> ac3)
      Press [q] to stop, [?] for help
      frame=12170 fps=343 q=21.2 size=   24850kB time=00:08:27.57 bitrate= 401.1kbits/s    

команда выполняется без ошибок. Но когда в открытом файле нет звука. это только показывает видео. Но файл mp4 проигрывается с аудио и видео.

Есть ли что-то, что мне не хватает при преобразовании в AC3 аудио кодек.

bash$ mplayer output.mpg
      MPlayer SVN-r36498-snapshot-4.8.2 (C) 2000-2013 MPlayer Team
      206 audio & 433 video codecs
      mplayer: could not connect to socket
      mplayer: No such file or directory
      Failed to open LIRC support. You will not be able to use your remote control.

      Playing  output.mpg.
      libavformat version 55.19.104 (internal)
      MPEG-PS file format detected.
      MPEG: No audio stream found -> no sound.
      VIDEO:  MPEG1  512x272  (aspect 1)  23.976 fps    0.0 kbps ( 0.0 kbyte/s)
      Load subtitles in ./
      Opening video filter: [expand osd=1 aspect=16/9 round=16]
      Expand: -1 x -1, -1 ; -1, osd: 1, aspect: 1.777778, round: 16
      ==========================================================================
      Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
      libavcodec version 55.39.100 (internal)
      Selected video codec: [ffmpeg1] vfm: ffmpeg (FFmpeg MPEG-1)
      ==========================================================================
      Audio: no sound
      Starting playback...
      [VD_FFMPEG] Trying pixfmt=0.
      [VD_FFMPEG] XVMC-accelerated MPEG-2.
      The selected video_out device is incompatible with this codec.
      Try appending the scale filter to your filter list,
      e.g. -vf spp,scale instead of -vf spp.
      [VD_FFMPEG] Trying pixfmt=1.
      [VD_FFMPEG] XVMC-accelerated MPEG-2.
      The selected video_out device is incompatible with this codec.
      Try appending the scale filter to your filter list,
      e.g. -vf spp,scale instead of -vf spp.
      [VD_FFMPEG] Trying pixfmt=3.
      [VD_FFMPEG] XVMC-accelerated MPEG-2.
      The selected video_out device is incompatible with this codec.
      Try appending the scale filter to your filter list,
      e.g. -vf spp,scale instead of -vf spp.
      Movie-Aspect is 1.88:1 - prescaling to correct movie aspect.
      VO: [xv] 512x288 => 512x288 Planar YV12 
      New_Face failed. Maybe the font path is wrong.
      Please supply the text font file (~/.mplayer/subfont.ttf).
      subtitle font: load_sub_face failed.
      New_Face failed. Maybe the font path is wrong.
      Please supply the text font file (~/.mplayer/subfont.ttf).
      subtitle font: load_sub_face failed.
      [mpeg1video @ 0xb75a8d20]ac-tex damaged at 12 0
      [mpeg1video @ 0xb75a8d20]Warning MVs not available
      [mpeg1video @ 0xb75a8d20]concealing 544 DC, 544 AC, 544 MV errors in I frame

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