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• Get PTS from raw H264 mdat generated by iOS AVAssetWriter

  26 décembre 2012, par kolyuchiy

  I'm trying to simultaneously read and write H.264 mov file written by AVAssetWriter. I managed to extract individual NAL units, pack them into ffmpeg's AVPackets and write them into another video format using ffmpeg. It works and the resulting file plays well except the playback speed is not right. How do I calculate the correct PTS/DTS values from raw H.264 data ? Or maybe there exists some other way to get them ?

  Here's what I've tried :

  1. Limit capture min/max frame rate to 30 and assume that the output file will be 30 fps. In fact its fps is always less than values that I set. And also, I think the fps is not constant from packet to packet.

  2. Remember each written sample's presentation timestamp and assume that samples map one-to-one to NALUs and apply saved timestamp to output packet. This doesn't work.

  3. Setting PTS to 0 or AV_NOPTS_VALUE. Doesn't work.

  From googling about it I understand that raw H.264 data usually doesn't contain any timing info. It can sometimes have some timing info inside SEI, but the files that I use don't have it. On the other hand, there are some applications that do exactly what I'm trying to do, so I suppose it is possible somehow.

• lavc/h264dec : don't error out when receiving multiple IDR slices

  26 septembre 2018, par Josh de Kock

  lavc/h264dec : don't error out when receiving multiple IDR slices
  This error isn't particularly helpful as checking for mixed IDR/non-IDR
  
  NALUs would need to be done at a higher level to actually be accurate.
  
  Removing the error allows an API user to send individual slice NALUs
  
  (i.e. incomplete frames) so they can take advantage of slice
  
  threading. The ticket which this error was added for (#4408) no
  
  longer segfaults after removing this error (as the bug was likely
  
  fixed more properly elsewhere).
  

  • [DH] libavcodec/h264dec.c

• avformat/hlsenc : Check that data is set

  21 janvier 2018, par Brendan McGrath

  avformat/hlsenc : Check that data is set
  If codecpar->extradata is not set (for example, when the stream goes
  
  through the 'tee' muxer), then a segfault occurs.
  
  This patch ensures the data variable is not null before attempting
  
  to access it
  
  Before the var_stream_map option was available - I was using the tee
  
  muxer to create each resolution as an individual stream.
  
  When running this configuration after the most recent hlsenc change
  
  I hit a segfault
  
  The most simple command which recreates the segfault is :
  
  ffmpeg -i in.ts -map 0:a -map 0:v -c:a aac -c:v h264 -f tee [select=\'a,v\':f=hls]tv_hls_hd.m3u8
  Signed-off-by : Brendan McGrath <redmcg@redmandi.dyndns.org>
  

  • [DH] libavformat/hlsenc.c