[FFmpeg-devel] [PATCH] Frame rate emulation

Luca Abeni lucabe72
Thu Jun 28 11:40:47 CEST 2007


Luca Abeni wrote:
>>> If we switch AVFormats to a non-blocking behaviour, we will have to 
>>> properly update ffmpeg.c too (and we will probably have to increase some 
>>> version number).
>> we could add a flag which enables non blockng behavior
> Yes, I like this idea. I'll work on it as soon as I find some time, and 
> I submit a patch introducing the new avformat flag, and updating v4l2.c
Here is a first try... I've not been able to test the patch, but I think 
it should not break anything ;-)

The patch introduces a new AVFMT_FLAG_NONBLOCK flag, and updates v4l2.c 
to support it (I did not split it in two patches, because the first one 
would be really trivial... If needed, I'll split the patch for committing).
I think the other "blocking input formats" can be updated in a second time.

I assume that VIDIOC_DQBUF can return EAGAIN only if the device is 
opened in non-blocking mode, so AVFMT_FLAG_NONBLOCK is not tested before 
returning AVERROR(EAGAIN). If this assumption is wrong (but from the 
v4l2 documentation I think it is not), I have a second version of the 
patch which always tests AVFMT_FLAG_NONBLOCK...

Finally, I am returning AVERROR(EAGAIN), but... Is this the correct 
thing to do? Looking at audio.c, it seems that when the driver would 
block the packet size is set to 0 and 0 is returned... To be safe, I 
also set pkt->size to 0, but I do not know if this is really needed. Let 
me know, and I'll fix the patch in the proper way.

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