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• Fix CBR output for IP multicasting video

  19 août 2014, par ddhung

  I’m using ffmpeg for transcoding live ip multicasting video on server linux Centos 5.9 OS. This is my ffmpeg command

  ffmpeg -i "udp:// x.x.x.x:6000?fifo_size=1000000&overrun_nonfatal=1&timeout=1000000" -filter:v yadif=0:-1:1 -vcodec libx264 -vprofile main -level 30 -tune zerolatency -pass 1 -b:v 900k -minrate 900k -maxrate 900k -bufsize 900k -x264opts nal_hrd=cbr:rc_lookahead=40:interlaced=1:scenecut=0:cabac=1:keyint=120:deblock=0,0:aud=1:qpmin=16:qpmax=51:qpstep=10:ref=2:mixed-refs=1:subme=9:me=esa:chroma_me=0:merange=64:8x8dct=0:fast_pskip=0:chroma_qp_offset=0:trellis=2:psy=0:bframes=0:weightp=2:sliced_threads -s:v 720x576 -r:v 25 -force_key_frames 'expr:gte(t,n_forced*3)' -threads 0 -acodec aac -strict -2 -ac 1 -ar 32000 -b:a 32k -filter:a volume=1 -f mpegts -muxrate 1400k udp://x.x.x.x:6000?pkt_size=1316

  My output video is for broadcasting so I have to configure CBR video output by feature –muxrate. But when I watch this stream on VLC the bitrate change very much not constant. The null packet is very high to force cbr mpeg2ts output.

  I also measure IP output video by HST3000 JDSU equipment and I see the measurement result is very bad as images.
  The PCR Jitter, IGMP Latency, Jitter Max which is not good as measurement standard by JDSU

  I try many way to change the ffmpeg command but not successful. The bitrate changes sometime > 1400kbps a lot. I think the problem may be the bitrate not constant. I have heard to change the muxrate output is CBR, it had to be change the code C mpegtsenc.c in libavformat library to new patch.
  So could you help me fix this problem and make the measurment result is better.
  Thank you so much.

  Best Regards

• How to debug ffmpeg c code used in IJKmediaplayer ?

  15 août 2015, par Daniyal Yasin

  I am trying to use the libstagefright codec of ffmpeg to decode an mp4 file using IJKmediaplayer on android. IJKmediaplayer is sort of a wrapper enabling the use of ffmpeg on Android.

  This is the link giving basic info about ijkmediaplayer : https://github.com/Bilibili/ijkplayer

  The link also describes the build process for ijkmediaplayer. First ffmpeg is built then the shared libraries are copied to appropriate places and then I have to import the project in eclipse.

  I use the ijkmediaplayer android project in eclipse as a library project in another android application. The structure is like this :

  |-ijkmediaplayer
  
  | |-jni
  
  |   |-ffmpeg (this folder doesn't have the complete source just headers)
  
  |   |-ijkmedia (some c source files of ijkmediaplayer)
  
  |
  
  |-my_project

  So my question is how do I debug libstagefright.cpp from my application ?

  Libstagefright.cpp is contained in the ffmpeg source not visible in the android ijkmediaplayer project. But used when building the ijkmediaplayer android project as described in the link.

  The debugger easily reaches the code of the ijkmediaplayer android project. But does not proceed to the native code automatically if I press f5.

• avcodec/mpeg4videodec : Remove always-true checks

  12 octobre 2022, par Andreas Rheinhardt

  avcodec/mpeg4videodec : Remove always-true checks
  codec_id is always AV_CODEC_ID_MPEG4 for mpeg4_decode_mb(),
  
  as the MPEG-4 decoder is the only decoder for which
  
  ff_mpeg4_decode_picture_header() as well as decode_init()
  
  are ever called and these are the only places where
  
  the decode_mb function pointer is ever set to mpeg4_decode_mb().
  
  ff_mpeg4_workaround_bugs() is also only called for the MPEG-4
  
  decoder (the caller checks the codec id).
  (ff_mpeg4_decode_picture_header() is also called for the MPEG-4
  
  parser, but it never uses the decode_mb function pointer.)
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/mpeg4videodec.c