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• ffmpeg audio - video sync issue (audio ahead of video) - while screen recording using x11grab

  12 juillet 2023, par maheshg

  While screen-recording using the below ffmpeg options I consistently get audio ahead of video, delay is in the order of few seconds

  


  ffmpeg cmd :

  


  ffmpeg -y -f x11grab -thread_queue_size 1024 -draw_mouse 0 -video_size 1920x1080 -i :0 -f pulse -thread_queue_size 1024 -i default -c:v libx264 -threads 0 -preset faster -c:a flac -async 1 -vsync 1 -crf 30 -crf_max 33 -f matroska output.mkv

  


  ffprobe output below :

  


  $ ffprobe demo.mkv 
ffprobe version 3.4.4-1~16.04.york0 Copyright (c) 2007-2018 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609
  configuration: --prefix=/usr --extra-version='1~16.04.york0' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  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
Input #0, matroska,webm, from 'demo.mkv':
  Metadata:
    ENCODER         : Lavf57.71.100
  Duration: 01:00:31.93, start: 0.000000, bitrate: 416 kb/s
    Stream #0:0: Video: h264 (High), yuv420p(progressive), 1920x1080, 29.97 fps, 29.97 tbr, 1k tbn, 59.94 tbc (default)
    Metadata:
      ENCODER         : Lavc57.89.100 libx264
      DURATION        : 01:00:31.928000000
    Stream #0:1: Audio: flac, 48000 Hz, stereo, s16 (default)
    Metadata:
      ENCODER         : Lavc57.89.100 flac
      DURATION        : 01:00:30.912000000


  


  I have even tried using avoid_negative_ts flag, but it didnt help with the sync issue.

  


  


  OS : Ubuntu-18.04

  


  ffmpeg version : 3.4

  


  


  Update : (with ffmpeg-4.0)
I have since split this process into 2 parts and tried as shown below (quality is better, but audio/video sync is still an issue)

  


  # STEP-1: screen recording
/usr/bin/ffmpeg -y -f x11grab -thread_queue_size 1024 -draw_mouse 0 \
-video_size 1920x1080 -i :91141925 -f pulse -thread_queue_size 1024 \
-i virtual_sink.monitor -c:v libx264rgb -threads 0 -preset ultrafast \
-c:a flac -ac 1 -crf 0 -f matroska output.mkv

# STEP-2: audio/video encoding
/usr/bin/ffmpeg -y -i output.mkv -c:v libx264 -threads 0 \
-preset faster -pix_fmt yuv420p -c:a copy -ac 1 -crf 25 \
-f matroska final_output.mkv


  


  STEP-1 uses much less CPU during screen recording, but audio is still ahead of video. the display I am using is xvfb one in STEP-1 (since, this is a headless machine in the cloud)

  


  Also, i have tried flags -filter_complex aresample=44100 -vsync 1 in STEP-1 to no avail.

  


  Can someone please help !

  


  


  Update 2 : (with latest ffmpeg from git master)

  


  IT WORKED ! THANKS @llogan for the helpful comments.

  


  


• process statuse is sombi after kill the process that opened in python subprocess.Popen and killed by subprocess.kill

  13 décembre 2018, par Eliya

  I’m using python with subprocess.Popen() to start FFmpeg with input live radio streaming URL and makes wav file every 30 seconds.
  When I try to kill the process with subprocess.kill() it works, But the process is still write in /proc/ and if I check-in system monitor the status of the process is "Zombi".

  Until the python script is done, So the process removed from /proc and I don’t see it in the system monitor.

  How can I kill the process without closed the python script ?

  here is example

  #! /usr/bin/python3 
  
  import os
  
  import subprocess
  
  import time
  
  
  
  # Start ffmpeg in background.
  
  folder_name = "path_to_file"
  
  input_ = "https://kanlivep2event-i.akamaihd.net/hls/live/749629/749629/kanmoreshet_mp3/chunklist.m3u8"
  
  ffmpeg_cmd = [
  
          "ffmpeg",
  
          "-y",
  
          "-loglevel", "8",
  
          "-thread_queue_size", "1500",
  
          "-i", input_,
  
          "-c", "copy",
  
          "-vn",
  
          "-f", "segment",
  
          "-segment_time", "30",
  
          "-ar", "8000",
  
          "-acodec", "pcm_s32le",
  
          "-ac", "1",
  
          "-strftime", "1",
  
          str(folder_name + '/' + input_.replace("/","") + '_*_*_%s.wav')
  
      ]
  
  process = subprocess.Popen(ffmpeg_cmd)
  
  # Check if the process is exist
  
  def check_exist(process):
  
      print("pid - ", process.pid)
  
      if os.path.isdir("/proc/{}".format(process.pid)):
  
          print ("Yes")
  
      else:
  
          print("No")
  
  
  
  check_exist(process)
  
  process.kill()
  
  time.sleep(20)
  
  check_exist(process)

• Having issues with kdenlive screen capture mode

  5 décembre 2018, par brianH

  Am running new repository install of kdenlive on ubuntu 18.04 after having similar problem on 16.04 but the problem persists "failed to start the capture application" when i start in screen capture mode. This problem was also present when I used kdenlive appImages.
  The current kdenlive version is 17.12.3 and i’ve tried changing kdenlive config settings, switching to default settings etc. also cleaned the /.cache/kdenlive file ..

  Ironically, when I use gdb kdenlive then run, the capture device works. Although then there is a separate issue of playing the video with the project monitor.

  On the previous 16.04 build had an addition log message that libvorbis was not recognized when the capture application failed.

  I had purged, autoremove packages and Resinstalled, also reinstalled ffmpeg and the installed libvorbis packages.
  Running ffmpeg gives :
  ffmpeg version 3.4.4-0ubuntu0.18.04.1 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
  configuration : —prefix=/usr —extra-version=0ubuntu0.18.04.1 —toolchain=hardened —libdir=/usr/lib/x86_64-linux-gnu —incdir=/usr/include/x86_64-linux-gnu —enable-gpl —disable-stripping —enable-avresample —enable-avisynth —enable-gnutls —enable-ladspa —enable-libass —enable-libbluray —enable-libbs2b —enable-libcaca —enable-libcdio —enable-libflite —enable-libfontconfig —enable-libfreetype —enable-libfribidi —enable-libgme —enable-libgsm —enable-libmp3lame —enable-libmysofa —enable-libopenjpeg —enable-libopenmpt —enable-libopus —enable-libpulse —enable-librubberband —enable-librsvg —enable-libshine —enable-libsnappy —enable-libsoxr —enable-libspeex —enable-libssh —enable-libtheora —enable-libtwolame —enable-libvorbis —enable-libvpx —enable-libwavpack —enable-libwebp —enable-libx265 —enable-libxml2 —enable-libxvid —enable-libzmq —enable-libzvbi —enable-omx —enable-openal —enable-opengl —enable-sdl2 —enable-libdc1394 —enable-libdrm —enable-libiec61883 —enable-chromaprint —enable-frei0r —enable-libopencv —enable-libx264 —enable-shared
  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

  Any thoughts on this ?