[FFmpeg-devel] [PATCH v3 1/1] avdevice/gdigrab: Add use_captureblt option for disable or use CAPTUREBLT flag, when useing the bitblt function with CAPTUREBLT it caused the mouse cursor flicker. most time we don't need this flag to capture window

[Marton Balint]

On Tue, 31 Dec 2019, fgodt wrote:

>
> On 2019/12/31 上午1:37, Calvin Walton wrote:
>> On Mon, 2019-12-30 at 12:31 +0100, Marton Balint wrote:
>>> On Mon, 30 Dec 2019, fgodtdev at hotmail.com wrote:
>>>
>>>> From: FgoDt <fgodtdev at hotmail.com>
>>>> + at item use_captureblt
>>>> +When use gdigrab to capture window or desktop, the mouse cursor
>>>> will flicker.
>>> Why? Does this happen with every windows version? This does not seem
>>> like
>>> the right fix. In fact, I dont't see how this can work, because mouse
>>> is
>>> drawn upon the captured video "manually" in paint_mouse_pointer.
>>> Could you
>>> dig deeper what is the main cause of the issue?
>> I'm guessing that what happens here is that on some OS versions, with
>> some graphics drivers, the cursor on the *real* display might flicker
>> while ffmpeg is capturing. I've never actually seen this happen, but if
>> you have bad/old drivers and have desktop compositing disabled, maybe?
> sorry i'm not describe clear. as you say the capture video mouse is 
> "manually" paint,
>
> so the flicker is not the video, but windows mouse cursor. the reason is 
> CAPTUREBLT flag
>
> use to capture layered window, and the animated cursors or software 
> cursor became know
>
> as layered window in Windows. so when we call bitblt with CAPTUREBLT 
> windows will hide
>
> cursor do capture , and then reshow the cursor,this will make Windows 
> mouse cursor flicker.
>
> if user not capture layered window, without CAPTUREBLT flag does not 
> change anything.
>
> see details 
> https://docs.microsoft.com/en-us/previous-versions/technet-magazine/dd392008(v=msdn.10)?redirectedfrom=MSDN

This is still not the whole story, if you google deeper you should find 
that this only affects Windows XP and earlier or Windows 7 if Aero is 
disabled.

Considering this, I am not sure if we should add this flag, 
maybe a warning should be printed instead if Aero is disabled.

Regards,
Marton