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• ffmpeg how to ensure audio+video synchronization ?

  22 juin 2020, par roko

  im using this conmmand :

  


  /usr/bin/ffmpeg \
-f pulse -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor \
-f pulse -i alsa_input.pci-0000_00_1b.0.analog-stereo \
-f x11grab -video_size 2560x1600 -framerate 8 -i :0.0 \
-filter_complex "amix=inputs=2[a]" \
-map 2:v -map '[a]' \
-c:a aac -b:a 128k \
-c:v h264_nvenc -b:v 1500k -maxrate 1500k -minrate 1500k \
-override_ffserver -g 16 http://10.100.102.18:8090/feed1.ffm


  


  my goal is to record screens continuously for long time (all the year)

  


  this is my ffmpeg version (running on RedHat 7.4) :

  


  ffmpeg version 3.4.7 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-39)
  configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --docdir=/usr/share/doc/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' --extra-ldflags='-Wl,-z,relro ' --extra-cflags=' ' --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvo-amrwbenc --enable-version3 --enable-bzlib --disable-crystalhd --enable-fontconfig --enable-gcrypt --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libcdio --enable-libdrm --enable-indev=jack --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libmp3lame --enable-nvenc --enable-openal --enable-opencl --enable-opengl --enable-libopenjpeg --enable-libopus --disable-encoder=libopus --enable-libpulse --enable-librsvg --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxvid --enable-libzvbi --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-libmfx --enable-runtime-cpudetect
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100


  


  when i run these command i get warning : non monotonous dts in output stream 0:1. this is the output :

  


  [pulse @ 0x13832c0] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
Output #0, ffm, to 'http://193.100.200.206:8090/feed1.ffm':
  Metadata:
    creation_time   : now
    encoder         : Lavf57.83.100
    Stream #0:0: Video: h264 (h264_nvenc) (Main), bgr0(progressive), 1920x1080, q=-1--1, 1500 kb/s, 8 fps, 1000k tbn, 8 tbc
    Metadata:
      encoder         : Lavc57.107.100 h264_nvenc
    Side data:
      cpb: bitrate max/min/avg: 1500000/0/1500000 buffer size: 3000000 vbv_delay: -1
    Stream #0:1: Audio: aac (LC), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      encoder         : Lavc57.107.100 aac
[aac @ 0x13dda80] Queue input is backward in time0:00:00.27 bitrate=5907.7kbits/s speed=0.552x    
[ffm @ 0x13bd5c0] Non-monotonous DTS in output stream 0:1; previous: 320000, current: -195354; changing to 320001. This may result in incorrect timestamps in the output file.                                                              
[ffm @ 0x13bd5c0] Non-monotonous DTS in output stream 0:1; previous: 320001, current: -174021; changing to 320002. This may result in incorrect timestamps in the output file.                                                              
[ffm @ 0x13bd5c0] Non-monotonous DTS in output stream 0:1; previous: 320002, current: -152688; changing to 320003. This may result in incorrect timestamps in the output file.                                                              
[ffm @ 0x13bd5c0] Non-monotonous DTS in output stream 0:1; previous: 320003, current: -131354; changing to 320004. This may result in incorrect timestamps in the output file.                                                              
[ffm @ 0x13bd5c0] Non-monotonous DTS in output stream 0:1; previous: 320004, current: -110021; changing to 320005. This may result in incorrect timestamps in the output file.                                                              
[ffm @ 0x13bd5c0] Non-monotonous DTS in output stream 0:1; previous: 320005, current: -88688; changing to 320006. This may result in incorrect timestamps in the output file.                                                               
[ffm @ 0x13bd5c0] Non-monotonous DTS in output stream 0:1; previous: 320006, current: -67354; changing to 320007. This may result in incorrect timestamps in the output file


  


  when i use -async 1 the warning disapear but, when i play audio file, the audio is Stretches/squeezes for few seconds at the begining and in the end.

  


  how can i ensure that audio and video always stay synchronize ?

  


  does another ffmpeg version fix this problem ? (can i install ffmpeg 4.2.3 on redhat 7.4/7.7) (i know that there is asyncts flag but i dont have it in my version)

  


  Please help me to find solution in order to keep synchronization for long recording.

  


• cbs : Ensure that reference fields always follow the associated pointer

  27 juillet 2020, par Mark Thompson

  cbs : Ensure that reference fields always follow the associated pointer
  Having these together allows us to find both pointers given the address
  
  of only one of them.
  

  • [DH] libavcodec/cbs_av1.h
  • [DH] libavcodec/cbs_h264.h
  • [DH] libavcodec/cbs_h265.h
  • [DH] libavcodec/cbs_jpeg.h
  • [DH] libavcodec/cbs_mpeg2.h
  • [DH] libavcodec/cbs_vp9.h

• FFmpeg - how to ensure dropping delayed frames

  2 septembre 2020, par user3469024

  I am using ffmpeg and mpv, to stream audio/video between two hosts. One of the hosts is sending stream with ffmpeg :

  


  ffmpeg -f pulse -thread_queue_size 0 -i audioInput -f video4linux2 -thread_queue_size 0 -standard PAL -i videoInput -vcodec mpeg4 -r 10 -s 176x144 -maxrate 256K -acodec pcm_s16le -ar 8000 -b:a 32k -af aresample=async=1000 -f rtsp -rtsp_transport tcp url


  


  and second host is receiving with mpv :

  


  mpv url --rtsp-transport=tcp --profile=low-latency --demuxer-lavf-o=rtsp_flags=listen --no-cache --autosync=30 --no-demuxer-thread --demuxer-lavf-analyzeduration=0 --demuxer-lavf-probesize=32


  


  I have tried a lot of options and combinations to reduce latency as much as possible. Above commands works nice, the latency on startup is < 1s. Unfortunately, sometimes, delay appears during streaming and it can even increase in time. My goal is to ensure, that delay will be more or less constant (close to 1s), and if some delay will appear, delayed frames will be dropped (even if it will affect audio or video quality).

  &#xA;

  How to force ffmpeg/mpv to drop frames, which are delayed e.g. more than 1s ?

  &#xA;