[FFmpeg-devel] [WIP] XComposite window capture demuxer (Linux)

[Emanuele Oriani]

 > If that was the only concern against it, then I'd say it is acceptable.
 > But there are some other concerns, also it seems to me xcbgrab can be
 > improved to reach the same smoothness as this attempt, and that was the
 > main distinctive feature of it. With that advantage lost, I'd say fixing
 > xcbgrab is the better bet.

I would think yes - that would be a good outcome - but please note 
xcbgrab doesn't seem to work when a window is borderless and/or full 
screen - which sorts of defeat the purpose of capturing 3d apps running 
full screen?

Do you have a patch for xcbgrab? I will try and capture similar video.

If the patch is about the av_sleep(half_expected_time), the code of 
xcomposite uses the very same logic (heavily inspired by it), but it 
works smoother - it would be interesting to see CPU usage of xcbgrab 
after the patch.

On 20/05/2020 07:28, Marton Balint wrote:
> 
> 
> On Tue, 19 May 2020, Nicolas George wrote:
> 
>> Marton Balint (12020-05-19):
>>> As Nicolas mentioned, kmsgrab practically requires root. Also, I 
>>> tried it on
>>> Intel half a year ago on Ubuntu 18.04, and it simply does not work
>>> correctly. There were crashes, there were random failures with 
>>> cryptic error
>>> messages, usually at the beginning of the capture, somtimes in the 
>>> middle of
>>> it. And the captured frame was missing some of the drawn opengl 
>>> primitives,
>>> it looked like kmsgrab grabbed the frame from the back buffer and not 
>>> the
>>> front.
>>>
>>> So kmsgab on Intel is a no-no for me.
>>
>> Thanks for the confirmation.
>>
>> Could you weigh in on the issue of filters/devices changing the OpenGL
>> global state, please?
> 
> If that was the only concern against it, then I'd say it is acceptable. 
> But there are some other concerns, also it seems to me xcbgrab can be 
> improved to reach the same smoothness as this attempt, and that was the 
> main distinctive feature of it. With that advantage lost, I'd say fixing 
> xcbgrab is the better bet.
> 
> Regards,
> Marton
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