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• FFMPEG : Sync problem between audio and video on Live Stream

  20 mai 2022, par zeitnot

  I am using NGINX RTMP as an RTMP server and FFMPEG as a client for live stream. When I connect to the RTMP server with the following command, I get an output file that contains slow motion for almost 5 seconds. But the sound is OK.

  


  ffmpeg -re -i rtmp://somertmp -c copy -f flv rtmp://a.rtmp.youtube.com/live2/sometoken -f flv output.mp4


  


  As the preceding example shows, I deliver the stream to youtube and at the same time, I get a copy. Youtube does not show slow motions but when I open the file with ffplay I can see the problematic frames.

  


  I want to fix these slow motions and make it synced with audio with ffmpeg or if not possible I want to tell ffmpeg to cut those slow frames along with audio channel so video and audio would be synced.

  


  For days, I am trying to find a solution for this problem but unfortunately, I could not. Any help will be appreciated.

  


• Audio-Video Delay When Fetching From NGINX-RTMP live-Mode

  17 novembre 2020, par Suuuehgi

  We get an RTSP-stream and mix it together with line-in over pulseaudio.

  


  This looks something like :

  


  ffmpeg \&#xA;  -use_wallclock_as_timestamps 1  -fflags &#x2B;genpts    \&#xA;  -max_delay 2000000 -thread_queue_size 1024         \&#xA;  -i "rtsp://url"           \&#xA;  -use_wallclock_as_timestamps 1  -fflags &#x2B;genpts    \&#xA;  -max_delay 2000000 -thread_queue_size 1024         \&#xA;  -itsoffset <offset>       \&#xA;  -f pulse                  \&#xA;  [...]&#xA;</offset>

  


  So far so good. This kind of works when fetching the rtsp stream directly.

  


  As soon as we route the RTSP-stream through an NGINX-RTMP loopback
(live mode) beforehand,

  


  ffmpeg -i rtsp://url -c copy -an -f flv rtmp://localhost/live&#xA;&#xA;ffmpeg \&#xA;  -use_wallclock_as_timestamps 1  -fflags &#x2B;genpts    \&#xA;  -max_delay 2000000 -thread_queue_size 1024         \&#xA;  -i "rtmp://localhost/live"                         \&#xA;  -use_wallclock_as_timestamps 1  -fflags &#x2B;genpts    \&#xA;  -max_delay 2000000 -thread_queue_size 1024         \&#xA;  -itsoffset <offset>                                \&#xA;  -f pulse                                           \&#xA;  [...]&#xA;</offset>

  


  we get a delay of close to 5 s within the output (audio-video offset).

  


  Whereat the configuration of rtmp ://localhost/live is :

  


  application live {
      live on;
      sync 10ms;
      record off;
      allow publish 127.0.0.1;
      deny publish all;
      }


  


  What causes the delay and how to get rid of it ?

  


  The RTMP-server itself does not cause a noticeable delay, I hence
assume this to be a timestamp issue but my wisdom ends with the above
written options.

  


• html process video on remote host and display live preview of processing

  12 juillet 2016, par CodeDezk

  I need to create a website where user able to upload the video to a server(a Linux PC with some video processing lib installed, like ffmpeg, opencv) and select the processing require and start it. And the user should able to see the processing of the video on live with rectangle draw on each frame.

  Like if user need to draw a rectangle on every frame, then upon click start the web page should start streaming the processing video on live.

  Is there anything exists to accomplish such an application. Any suggestion or tips ?