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

[Clément Bœsch]

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.

[...]

-- 
Clément B.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 473 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20151031/3d4683da/attachment.sig>