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• avformat/matroskaenc : handle AV1 extradata in packet side data

  11 août 2018, par James Almer

  avformat/matroskaenc : handle AV1 extradata in packet side data
  This is a temporary workaround for transcoding scenarious using libaom-av1
  
  encoder, which currently can't propagate extradata during initialization.
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavformat/matroskaenc.c

• lavc/h264 : create AVFrame side data from H.264 timecodes

  29 juin 2018, par Devin Heitmueller

  lavc/h264 : create AVFrame side data from H.264 timecodes
  Create SMPTE ST 12-1 timecodes based on H.264 SEI picture timing
  
  info.
  For framerates > 30 FPS, the field flag is used in conjunction with
  
  pairs of frames which contain the same frame timestamp in S12M.
  
  Ensure the field is properly set per the spec.
  

  • [DH] libavcodec/h264_sei.c
  • [DH] libavcodec/h264_sei.h
  • [DH] libavcodec/h264_slice.c
  • [DH] libavutil/frame.c
  • [DH] libavutil/frame.h

• How to get the real, actual duration of an MP3 file (VBR or CBR) server-side

  27 janvier 2021, par SquareCat

  I used to calculate the duration of MP3 files server-side using ffmpeg - which seemed to work fine. Today i discovered that some of the calculations were wrong. Somehow, for some reason, ffmpeg will miscalculate the duration and it seems to happen with variable bit rate mp3 files only.

  



  When testing this locally, i noticed that ffmpeg printed two extra lines in green.

  



  Command used :

  



  ffmpeg -i song_9747c077aef8.mp3


  



  ffmpeg says :

  



  [mp3 @ 0x102052600] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate


  



  After a nice, warm google session, i discovered some posts on this, but no solution was found.

  



  I then tried to increase the maximum duration :

  



  ffmpeg -analyzeduration 999999999 -i song_9747c077aef8.mp3


  



  After this, ffmpeg returned only the second line :

  



  [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate


  



  But in either case, the calculated duration was just plain wrong. Comparing it to VLC i noticed that there the duration is correct.

  



  After more research i stumbled over mp3info - which i installed and used.

  



  mp3info -p "%S" song_9747c077aef8.mp3


  



  mp3info then returned the CORRECT duration, but only as an integer, which i cannot use as i need a more accurate number here. The reason for this was explained in a comment below, by user blahdiblah - mp3info is simply pulling ID3 info from the file and not actually performing any calculations.

  



  I also tried using mplayer to retrieve the duration, but just as ffmpeg, mplayer is returning the wrong value.