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• ffmpeg keeps converting second ac3 audio stream to mp2

  19 juin 2015, par JMor

  I’m new to this forum, and hope someone can help.
  I am trying to add a second audio track (chinese.ac3) to an XVID video (vts_01.avi) that already has an ac3 track.

  These audio tracks are encoded to ac3, 48000 Hz, stereo, 128 kb/s, and I would like to keep them that way — just multiplex the streams without transcoding.

  This is the command I am using :

  ffmpeg -i vts_01.avi -vcodec copy -i Chinese.ac3 -acodec copy -map 0:0 -map 0:1 -map 1:0 muxed2.avi -newaudio

  ffmpeg does its work, except for the fact that it converts the second track to mp2, 64 kb/s.

  Here is a relevant excerpt from the output, where the key part is ’Stream #0.2 : Audio : mp2, 48000 Hz, stereo, s16, 64 kb/s’ where I would like ’Stream #0.2 : Audio : ac3, 48000 Hz, stereo, 128 kb/s’ :

  Input #0, avi, from 'vts_01.avi':
  
    Metadata:
  
      encoder         : Lavf53.5.0
  
    Duration: 02:03:26.40, start: 0.000000, bitrate: 1954 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 720x352 [PAR 1:1 DAR 45:22], 23.98 tbr,
  
  23.98 tbn, 23.98 tbc
  
      Stream #0.1: Audio: ac3, 48000 Hz, stereo, s16, 128 kb/s
  
  [ac3 @ 018A7440] max_analyze_duration 5000000 reached at 5024000
  
  [ac3 @ 018A7440] Estimating duration from bitrate, this may be inaccurate
  
  Input #1, ac3, from 'Chinese.ac3':
  
    Duration: 02:03:26.36, start: 0.000000, bitrate: 128 kb/s
  
      Stream #1.0: Audio: ac3, 48000 Hz, stereo, s16, 128 kb/s
  
  File 'muxed2.avi' already exists. Overwrite ? [y/N] y
  
  Output #0, avi, to 'muxed2.avi':
  
    Metadata:
  
      ISFT            : Lavf53.5.0
  
      Stream #0.0: Video: mpeg4, yuv420p, 720x352 [PAR 1:1 DAR 45:22], q=2-31, 23.
  
  98 tbn, 23.98 tbc
  
      Stream #0.1: Audio: ac3, 48000 Hz, stereo, 128 kb/s
  
      Stream #0.2: Audio: mp2, 48000 Hz, stereo, s16, 64 kb/s
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
    Stream #0.1 -> #0.1
  
    Stream #1.0 -> #0.2

  I have tried a number of different combinations, including explicitly forcing the stream to ac3 with :

  ffmpeg -i vts_01.avi -vcodec copy -i chinese.ac3 -acodec ac3 -ac 2 -ar 48000 -ab 128k -map 0:0 -map 0:1 -map 1:0 muxed2.avi -newaudio

  Same result.

  I have also tried to assign a codec to the stream with stream specifier(based on http://ffmpeg.org/ffmpeg.html#toc-Stream-specifiers-1, but these options are not recognized by my ffmpeg.

  I am running out of things to try.

• How to transmit videos directly from the website to RTMP server instead of using OBS ? [closed]

  28 décembre 2024, par Cường Lê Sỹ

  I had a server to receive a specific RTMP video like RTMP : //domain.com/show and use OBS to record videos, what I have to do to be able to record videos on my own website and transmit it. . Access RTMP server instead of using OBS or any code can do that, thank you

  


  I hope to be able to record videos directly on my website and play it back at the viewer page, like a livestream.

  


• Install PyAV on Windows

  16 juin 2015, par m.barz

  I got a problem building and thus setting up PyAV 32-bit on Windows 8 (x64). I tried the workflow for Windows as indicated in their documentation, but did not succeed :

  • I cross-compiled ffmpeg on Ubuntu 14.04 with the aid of a script.
  • I copied the *shared-install folder to Windows and set the PKG_CONFIG_PATH environment variable to the corresponding libs/pkgconfig path.
  • I copied the ffmpeg DLLs and its dependencies from the MinGW bin-folder to PyAV’s av folder as mentioned in PyAV’s docs.
  • I ran make build-mingw32 (where build-mingw32 is a recipe triggering python distutils like that : CFLAGS=$(CFLAGS) LDFLAGS=$(LDFLAGS) python setup.py build_ext --inplace -c mingw32)

  Finally I run into trouble with that last command. When the build process tries to create codec.pyd there is a bunch of undefined reference to _head_C_build27_cpython_PCBuild_libpython27_a errors leading gcc to fail. See cmd output below :

  

  I tried this on a fresh virtual machine running Windows 8.1 Pro having installed the MinGW toolchain including msys (I used the installer from mingw.org). I also tried the MinGW installer provided here.
  I hope someone already experienced similar issues using gcc and can help me with that !

  Thanks in advance and best regards,
  Michael