Recherche avancée

Sur d’autres sites (7490)

• avfilter/framesync : add a new option to set how to sync streams based on secondary...

  2 août 2022, par James Almer

  avfilter/framesync : add a new option to set how to sync streams based on secondary input timestamps
  Include two values for it, a default one that sets/keeps the current behavior,
  
  where the frame event generated by the primary input will have a timestamp
  
  equal or higher than frames in secondary input, plus a new one where the
  
  secondary input frame will be that with the absolute closest timestamp to that
  
  of the frame event one.
  Addresses ticket #9689, where the new optional behavior produces better frame
  
  syncronization.
  Reviewed-by : Nicolas George <george@nsup.org>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavfilter/framesync.c
  • [DH] libavfilter/framesync.h

• avcodec/h264_slice : don't sync default_ref[] between threads.

  18 juillet 2017, par Wan-Teh Chang

  avcodec/h264_slice : don't sync default_ref[] between threads.
  default_ref[] is unconditionally initialized in h264_initialise_ref_list()
  
  (called from ff_h264_build_ref_list(), called from h264_slice_init()).
  This fixes the following tsan warning when running fate-h264 :
  WARNING : ThreadSanitizer : data race (pid=31070)
  
    Write of size 8 at 0x7bbc000082a8 by thread T1 (mutexes : write M1628) :
  
      #0 memcpy /work/release-test/final/llvm.src/projects/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:655:5
  
  (ffmpeg+0x10de9d)
  
      #1 h264_initialise_ref_list ffmpeg/libavcodec/h264_refs.c:214:29 (ffmpeg+0x1186b3f)
  
      #2 ff_h264_build_ref_list ffmpeg/libavcodec/h264_refs.c:306 (ffmpeg+0x1186b3f)
  
      #3 h264_slice_init ffmpeg/libavcodec/h264_slice.c:1900:11 (ffmpeg+0x1191149)
  
  [..]
  
    Previous read of size 8 at 0x7bbc000082a8 by main thread (mutexes :
  
  write M1630) :
  
      #0 memcpy /work/release-test/final/llvm.src/projects/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:655:5
  
  (ffmpeg+0x10de9d)
  
      #1 ff_h264_update_thread_context ffmpeg/libavcodec/h264_slice.c:411:5 (ffmpeg+0x118b7dc)
  Signed-off-by : Wan-Teh Chang <wtc@google.com>
  
  Signed-off-by : Ronald S. Bultje <rsbultje@gmail.com>
  

  • [DH] libavcodec/h264_slice.c

• ffmpeg : Encoding a single live video stream into different resolutions and keeping them in sync

  15 mai 2020, par Almus

  I'm using NGINX as a simple HLS live video server. Sending an rtmp stream into the server, transcoding it into three different resolutions for delivery using HLS to users with different bandwidth limits.

  



  The problem I'm having is that when I take the 1080p 30fps input transcode it down to 480p and 720p then split it into chunks with HLS the segments from the two transcoded outputs are not in sync with the copied full resolution stream.

  



  here is what I am doing now :
exec FFmpeg on the source rtmp stream :

  



  exec ffmpeg -i rtmp://127.0.0.1:1935/live/$name
     -c:v libx264 -c:a aac -b:a 128k -vf "scale=-2:720" -vsync 1 -copyts -start_at_zero -sws_flags lanczos -r 30 -g 30 -keyint_min 30 -force_key_frames "expr:gte(t,n_forced*1)" -tune zerolatency -preset ultrafast -crf 28 -maxrate 2096k -bufsize 4192k -threads 16 -f flv rtmp://localhost:1935/show/$name_720
     -c:v libx264 -c:a aac -b:a 96k -vf "scale=-2:480" -vsync 1 -copyts -start_at_zero -sws_flags lanczos -r 30 -g 30 -keyint_min 30 -force_key_frames "expr:gte(t,n_forced*1)" -tune zerolatency -preset ultrafast -crf 28 -maxrate 1200k -bufsize 2400k -threads 16 -f flv rtmp://localhost:1935/show/$name_480
     -c copy -vsync 1 -f flv rtmp://localhost:1935/show/$name_src;


  



  Then take the results and segment them for HLS

  



  hls on;
hls_path /var/www/live-adapt;
hls_nested on;
hls_fragment 1;
hls_playlist_length 30;

hls_fragment_naming system;

hls_variant _480 BANDWIDTH=1200000; # Medium bitrate, SD resolution
hls_variant _720 BANDWIDTH=2048000; # High bitrate, HD 720p resolution
hls_variant _src BANDWIDTH=4096000; # Source bitrate, source resolution


  



  This is working except the streams are not in sync which causes issues if the end-users need to (or choose to) switch between streams.
Example :

  



  Sequence number 510 was not everywhere in sync:
PTS 510.7 for https://fqdn/live-adapt/c5d7ddb2-5562-4bd3-9e06-df9fa6e8ff06_480/1589521352937.ts
PTS 510.7 for https://fqdn/live-adapt/c5d7ddb2-5562-4bd3-9e06-df9fa6e8ff06_720/1589521352933.ts
PTS 511.699 for https://fqdn/live-adapt/c5d7ddb2-5562-4bd3-9e06-df9fa6e8ff06_src/1589521353752.ts


  



  I would love any advice or suggestions.