[FFmpeg-devel] [PATCH] Added QSV based VPP filter - second try

Ivan Uskov ivan.uskov at nablet.com
Thu Nov 5 14:28:30 CET 2015


Hello wm4,

Thursday, November 5, 2015, 3:42:30 PM, you wrote:

w> On Thu, 5 Nov 2015 12:49:50 +0100
w> "Sven Dueking" <sven at nablet.com> wrote:

>> > > +            } else if (ret == MFX_WRN_DEVICE_BUSY) {
>> > > +                av_usleep(500);  
>> > 
>> > What. Use proper event-based waiting.
It is not possible.
>> 
>> That´s the same behavior as we have in the qsv encoder and decoder.
>> And as far as I know this is how Intel recommends to handle this.

w> That's just ridiculous. Can you send some hate-mail to Intel and tell
w> them what a bad idea this is? Half a millisecond is an eternity for a
w> CPU. What if the device is blocked only for 10 microseconds? Then it
w> will waste time by spending 490 microseconds idly.
1. Please remember we use GPU, not CPU.
2.   500us  means that even we will get MFX_WRN_DEVICE_BUSY at every frame we
will    able     to    achieve    ~2000fps  performance.  It   looks   enough
performance level for any practical applications.
3.   In   real  life  MFX_WRN_DEVICE_BUSY does appear when GPU really busy by
other  tasks. So nothing bad will appear if one thread/process will sleep for
500us to make another thread complete its work.

w> Software engineers recognized that polling is a bad idea half a century
w> ago. Why can't Intel do this right?
May  be  because  it  is  complex to organize event-polling when calculations
performs in GPU?

w> Or does MFX have some sort of async mode that works without polling?
Does  NOT.  I'm  sorry  but  we  forced  to  use this way, since it is by QSV
design.

-- 
Best regards,
 Ivan                            mailto:ivan.uskov at nablet.com



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