[FFmpeg-devel] [PATCH] avfilter/vf_deshake: replace qsort with AV_QSORT

[Ganesh Ajjanagadde]

On Sat, Oct 31, 2015 at 6:19 AM, Nicolas George <george at nsup.org> wrote:
> Le nonidi 9 brumaire, an CCXXIV, Ganesh Ajjanagadde a écrit :
>> Sample benchmark (x86-64, Haswell, GNU/Linux):
>> File: original from https://trac.ffmpeg.org/ticket/1430
>> command: ffmpeg -stream_loop 8 -i file.webm -vf deshake=rx=64:ry=64 -f null -
>>
>> Timer truncated at 1024 runs.
>> new:
>> 39676 decicycles in qsort,    1024 runs,      0 skips
>>
>> old:
>>   86783 decicycles in qsort,    1024 runs,      0 skips
>
> What was inside the start/stop_timer block? I see that the qsort call is
> after a very expensive loop, I suspect those few thousand cycles may be
> completely negligible in front of the loop itself.

Entirely possible. I just did this as a low hanging fruit. I highly
suspect that the algorithm can be improved (see Michael's comment).
The start/stop was just around the qsort statement. Since you asked
this, I will add it to the commit message.

>
> Regards,
>
> --
>   Nicolas George
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>