[vlc-devel] [PATCH] codec: avcodec: no FRAME threading on unknown/low framerate

[Steve Lhomme]

On 22/08/2018 17:35, Francois Cartegnie wrote:
> Le 21/08/2018 à 21:06, Rémi Denis-Courmont a écrit :
>> Le tiistaina 21. elokuuta 2018, 19.27.46 EEST Francois Cartegnie a écrit :
>>> fixes always late frames due to threading delay
>> Unknown rate does not imply low rate.
> Unfortunately there's no way to guess frame rate in those cases without
> buffering (ie, make things worse).
>
> I don't know containers without frame rate info, or containing H26x not
> providing frame rate (VUI) outside of RTSP use case.

Matroska doesn't have a frame rate because it's designed for Variable 
Frame Rates. There's an informational default duration per frame which 
is used most of the time but it may not be there.

>
>> Given that we cannot safely enable hardware decoding with unknown rate,
>> blocking threaded decoding as well seems rather insane.
> Well, frame threaded, not slice threaded.
>
>> In other words, this might work around some bugs but it will also break stuff
>> that was working so far.
> I never seen an explanation of SLICE vs FRAME threading performance
> difference.
> There's only known broken/blacklisted ones with some codecs.
> The slice threading fallback can be limited to RTSP by tagging es fmt
> with a low delay flag.
>
> -- 
> Francois Cartegnie
> VideoLAN - VLC Developer
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