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

[Ganesh Ajjanagadde]

On Sat, Oct 31, 2015 at 9:59 AM, Clément Bœsch <u at pkh.me> wrote:
> On Sat, Oct 31, 2015 at 08:47:37AM -0400, Ganesh Ajjanagadde wrote:
>> 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).
>
> deshake is a filter that overall needs large rework. Aside from the fact
> that it doesn't work well (it's an unmaintained half assed simplified
> version of what vid.stab does), it is also IIRC easily crashable.
>
> Ticket #1430 may be of interest.

Just now pushed, and have a remark about it in the commit message
brought up by Nicolas's comment before reading your email :).

>
> [...]
>
> --
> Clément B.
>
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