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• Trouble writing mp3 into flv container

  8 février 2013, par Sriram

  I am encoding a raw pcm stream with LAME and writing the mp3 encoded samples to an flv container using a c program. For debugging purposes, I am also writing the mp3 encoded samples to a file separately. The following is observed :

  1. The mp3 written to another file is correct. There are no clicks or any other artefacts observed.

  2. The flv file does not play anything. Examining with ffmpeg like so :

     $ ./ffmpeg.exe -i temp_local_flv.flv

  The above command gives the following :

  ffmpeg version N-49352-gc46943e Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Jan 26 2013 12:12:14 with gcc 4.7.2 (GCC)
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  
    libavutil      52. 17.100 / 52. 17.100
  
    libavcodec     54. 91.100 / 54. 91.100
  
    libavformat    54. 61.104 / 54. 61.104
  
    libavdevice    54.  3.102 / 54.  3.102
  
    libavfilter     3. 34.101 /  3. 34.101
  
    libswscale      2.  2.100 /  2.  2.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  2.100 / 52.  2.100
  
  [flv @ 0000000000307be0] Stream discovered after head already parsed
  
  [mp3 @ 000000000237d9c0] Header missing
  
  Input #0, flv, from 'temp_local_flv.flv':
  
    Duration: 00:00:00.07, start: 0.002000, bitrate: 643 kb/s
  
      Stream #0:0: Audio: mp3, 22050 Hz, mono, s16p, 32 kb/s
  
      Stream #0:1: Data: none
  
  At least one output file must be specified  

  My questions :
  1. What is this "Header missing" ? Is there a "special" mp3 header that needs to be written when writing encoded samples to an flv container ? If so, what does the header contain ? And given that the mp3 samples written to the file are decoded correctly by an audio player, what am I missing ?

• avformat/oggenc : Avoid allocating and copying when writing page data

  3 mai 2020, par Andreas Rheinhardt

  avformat/oggenc : Avoid allocating and copying when writing page data
  When the Ogg muxer writes a page, it has to do three things : It needs to
  
  write a page header, then it has to actually copy the page data and then
  
  it has to calculate and write a CRC checksum of both header as well as
  
  data at a certain position in the page header.
  To do this, the muxer used a dynamic buffer for both writing as well as
  
  calculating the checksum via an AVIOContext's feature to automatically
  
  calculate checksums on the data it writes. This entails an allocation of
  
  an AVIOContext, of the opaque specific to dynamic buffers and of the
  
  buffer itself (which may be reallocated multiple times) as well as
  
  memcopying the data (first into the AVIOContext's small write buffer,
  
  then into the dynamic buffer's big buffer).
  This commit changes this : The page header is no longer written into a
  
  dynamic buffer any more ; instead the (small) page header is written into
  
  a small buffer on the stack. The CRC is then calculated directly via
  
  av_crc() on both the page header as well as the page data. Then both the
  
  page header and the page data are written.
  Finally, ogg_write_page() can now no longer fail, so it has been
  
  modified to return nothing ; this also fixed a bug in the only caller of
  
  this function : It didn't check the return value.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/oggenc.c

• avformat/movenc : initialize pts/dts of timecode packet

  14 mars 2022, par Limin Wang

  avformat/movenc : initialize pts/dts of timecode packet
  Fix below error message when timecode packet is written.
  
  "Application provided duration : -9223372036854775808 / timestamp : -9223372036854775808 is out of range for mov/mp4 format"
  try to reproduce by :
  
  ffmpeg -y -f lavfi -i color -metadata "timecode=00:00:00:00" -t 1 test.mov
  Note although error message is printed, the timecode packet will be written anyway. So
  
  the patch 2/2 will try to change the log level to warning.
  Fixes ticket #9488
  Signed-off-by : Limin Wang <lance.lmwang@gmail.com>
  

  • [DH] libavformat/movenc.c