[FFmpeg-user] dynamically sync video and audio - is it possible?

[Feurstein, Michael]

Example ffmpeg command using vsync and mapping option would be:

# syncing video (0.0) to audio (1.0)
ffmpeg -i udp://@224.0.0.1:1234 -vcodec copy -i http://192.168.1.12:8000 -acodec copy -re -threads 2 -vsync 2 -map 0.0:1.0 -map 1.0 -f mpegts udp://224.0.0.2:1236

# syncing audio (1.0) to video (0.0)
ffmpeg -i udp://@224.0.0.1:1234 -vcodec copy -i http://192.168.1.12:8000 -acodec copy -re -threads 2 -vsync 2 -map 0.0 -map 1.0:0.0 -f mpegts udp://224.0.0.2:1236

Both commands run - BUT - don't sync correctly.

Anyone know what I am doing wrong?

thx//mike


On May 26, 2011, at 2:19 PM, Feurstein, Michael wrote:

> Hi,
> 
> 
> My testruns show that when muxing an incoming udp stream with another audio stream the video stream always seems to be delayed plus minus 2  seconds. Is there a way to dynamically sync audio and video, or maybe tell ffmpeg to start muxing when both video and audio are available. I reckon the dynamic delay comes from opening the streams, therefore I can't assume a 2 second delay for each run, because sometimes the delay will be 3 seconds. My goal would be to automate this.
> 
> 
> 
> I already tried itsoffset, which only helps if I know the delay beforehand, which I don't.
> 
> 
> 
> I've been playing around with vsync and async as well as isync, but without success. The manual tells me I can sync one part (video or audio) to another, only thing is I can't find a working command setup
> 
> 
> 
> Does someone out there have knowledge in how to use vsync and map the audio to the video? Maybe an example?
> 
> If not... is it even possible what I want to achieve?
> 
> 
> 
> I appreciate any input.
> 
> 
> 
> Thanks and greetings!
> 
> Michael Feurstein
> 
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