[FFmpeg-devel] [PATCH] libavcodec/qsvdec.c: Restoring decoding functionality after unsuccessful merge from libav.

Hendrik Leppkes h.leppkes at gmail.com
Sun Jul 24 19:53:05 EEST 2016

On Sun, Jul 24, 2016 at 3:43 PM, Ivan Uskov <ivan.uskov at nablet.com> wrote:
> Hello Mark,
> Saturday, July 23, 2016, 11:42:46 PM, you wrote:
> MT> On 23/07/16 20:33, Ivan Uskov wrote:
>>> If  you are use qsv, I would like to recommend to roll-back to version before
>>> d30cf57a7b2097b565db02ecfffbdc9c16423d0e
>>> Really  the  d30cf57a7b2097b565db02ecfffbdc9c16423d0e is useless and only
>>> makes code complex and work slow, the sync variable is not mandatory to be
>>> allocated  on  heap  at  all.  libav  guys  did a big mistake when have added
>>> such "feature".
> MT> Are you sure that works correctly with all streams, maybe one with some
> MT> sort of delay?  It looks like you can add multiple things to the fifo in
> MT> one call and but then only ever remove one, so using the stack to hold
> MT> them across invocations is not appropriate (though failure may be very subtle).
> Yes, I'm sure.
> There are following arguments:
> 1. Intel's samples by itself use general variable for the 'sync' arg, not
> heap allocated.
> 2. Intel documentation says nothing special for this arg.
> 3. I did several qsv-based transcoders for windows and linux no any issues
> without this questionable trick.
> 4. A fifo object used previously to keep 'sync' handles already keeps data on
> heap :-)
> There only one known issue into initial implementation, the fifo size may be not
> enough an there is no check for overflow. So at some cases wrapper may
> overwrite sync entries in fifo and some decoded frames may be lost. But it is
> not related with discussed problem.
> MT> (Note that I'm not sufficiently familiar with Media SDK to confidently
> MT> assert anything about how this code should behave, so please don't read too much into what I say.)
> MT> In general I think if you are happy that the previous implementation in
> MT> ffmpeg was correct then please do revert, because the code as it is now is completely broken.
> Ok, will do.

Ivan, can you *please* fix your quoting style to use standard quotes
as everyone else (ie. single > for every level)? Reading your replies
is practically impossible.

- Hendrik

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