[FFmpeg-user] Low latency streaming from webcam

Roger Pack rogerdpack2 at gmail.com
Thu Jun 21 18:30:21 CEST 2012

> I did a test where I recorded 20 seconds of video and stored it in a file. Then
> I did the same thing but instead of storing data the entire time, for
> the first 10
> seconds I let ffmpeg and x264 sit there with the buffers full, then the last 10
> seconds I let cat loose on the end pipe. What I saw was the first two seconds of
> video, followed by the same frame for the next 8 seconds, followed by the last
> 10 seconds of video. The files ended up the same size (actually the
> second one is
> bigger by a few %).

My guess, knowing absolutely nothing about the problem, is that ffmpeg
write "the first 10 seconds" then blocks on the pipe, because nothing
is reading from it.  x264 then pulls in "the first 10 seconds" and,
while it is processing it, ffmpeg is unable to write until finally
x264 lets it start writing.  But that's just conjecture.

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