[FFmpeg-user] Low latency streaming from webcam

Tim Pitman tapitman11 at gmail.com
Fri Jun 22 22:16:35 CEST 2012

I modified my code to keep the pipes empty and it seems to be working
pretty well. Thanks for your input Roger.

I would still like to know what's going on in this situation, though...

On Thu, Jun 21, 2012 at 9:30 AM, Roger Pack <rogerdpack2 at gmail.com> wrote:
>> 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.
> -roger-
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