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

[Eric Beuque]

2016-06-20 9:57 GMT+02:00 Michael Niedermayer <michael at niedermayer.cc>:

> On Sun, Jun 19, 2016 at 11:42:42PM +0200, Eric Beuque wrote:
> > 2016-06-19 16:14 GMT+02:00 Michael Niedermayer <michael at niedermayer.cc>:
> >
> > > On Sun, Jun 19, 2016 at 09:59:22AM +0200, Eric Beuque wrote:
> > > > 2016-06-18 13:46 GMT+02:00 Michael Niedermayer
> <michael at niedermayer.cc>:
> > > >
> > > > > 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
> > > > >
> > > >
> > > > I don't really understand what will be changed in the decoder with or
> > > > without restriction...
> > >
> > > some of the features of h.264 will not decode "right" without the
> > > full resolution
> > >
> >
> > Ok what features do you mean? Maybe it's out of our scope.
>
> some restrictions on intra modes
> constrained intra prediction at least
> The GOP size should be small too and there may be other things
> like disabling the loop filter
>
> cant you just use the IP camera in lower resolution if memory is a
> problem ? maybe it can encode 2 streams of different resolution
>


Actually, we are already doing this, but sometimes it's not possible,
because some camera are not able to deliver two stream. It's just a
question to know if there is a way to improve the usage in that case. If
you tell me it's not, we will deal with that.



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