[FFmpeg-devel] Sponsoring feature for H.264 decoding with scaling factor (1/2, 1/4...) (if possible)

[Michael Niedermayer]

On Fri, Jun 17, 2016 at 07:26:59PM +0200, Eric Beuque wrote:
> 2016-06-17 19:16 GMT+02:00 Michael Niedermayer <michael at niedermayer.cc>:
> 
> > On Fri, Jun 17, 2016 at 05:39:23PM +0200, Eric Beuque wrote:
> > > Hi,
> > >
> > > i'm posting here for a feature that is missing in ffmpeg (or may be i
> > > missed something), which consist of decoding H.264 frame with a scaling
> > > factor of 1/2, 1/4, 1/8...
> > >
> > > I found the parameter lowres, which works well with MJPEG stream but it's
> > > not working with the H.264 decoder.
> > >
> > > I don't know if it's something possible to implement in the decoder, but
> > if
> > > yes, my compagny agreed to sponsor the feature (depending on the cost of
> > > course), if a developer qualified is interested to do it.
> > >
> > > Is someone know if it is possible, and if it can exist someone interested
> > > to develop this feature?
> >
> > is it acceptable if the encoder enforces some restrictions on the used
> > features ?
> >
> > most general h264 likely cannot efficiently be decoded in lower
> > resolution with acceptable quality
> > Restricting the used intra modes may make it possible to do it though
> > i dont know what the quality would be but better than without
> > restrictions
> >
> > [...]
> >
> 
> 
> Actually, the main goal is for motion detection algorithm, so we need small
> resolution and best quality is not required. We just need good estimation
> for the moving pixel.
> 
> For now, we decode in H.264, and scale it close 320x240, the then we
> perform motion detection on it. The goal is to speed up the process and
> reduce the memory usage since decoding a 2048x1536 picture lead around a 5
> MB for the decoded image in memory.
> 
> So i think it could be OK.

i dont think that withut restrictions it would be good enough for
motion detection

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No great genius has ever existed without some touch of madness. -- Aristotle
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