[Ffmpeg-devel] Re: [Ffmpeg-user] ffmpeg encoding, reallyslowvideo when recording with audio

Luca Abeni lucabe72
Fri Feb 3 15:39:40 CET 2006

Hi Erik,

On Fri, 2006-02-03 at 12:52 +0100, Erik Slagter wrote:
> I am curious how it long it will take before the first "bug" reports
> come in on Cynergy cards.
Well, I guess I will have to buy a cynergy card :)
I am stress-testing the v4l2 input and I cannot see big synchronization
problems. I also tried to disconnect the video input, to reproduce the
drivers' bug you described in a previous mail, but everything worked as
expected (no ioctl() failed). When I disconnected the video input, the
driver just provided blu frames at a low rate (about 1 frame per second,
I think), but v4l2.c could easily cope with this.

> These have a bad crystal that make audio and
> video go out of sync :-( Workaround is in the driver, but has to be
> enabled and tuned by the user.
Uhmm... Are you talking about the fact that there is a drift between the
"card time" (I mean, the one that is supposed to be increased by 40ms at
every video frame) and the "system time" (the one returned by
gettimeofday())? If yes, then that cannot be avoided in a real world :)
But ffmpeg can correctly cope with it (by dropping or duplicating video
frames... About one frame per hour on my system, if I remember well, but
I am not sure).
Or am I misunderstanding the problem?

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