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

Eric Beuque eric.beuque at gmail.com
Fri Jun 17 19:26:59 CEST 2016

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.

> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> In fact, the RIAA has been known to suggest that students drop out
> of college or go to community college in order to be able to afford
> settlements. -- The RIAA
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