[FFmpeg-devel] HAP QuickTime codec support

[Reimar Döffinger]

On Fri, Nov 14, 2014 at 08:59:45PM +0100, Reimar Döffinger wrote:
> On Fri, Nov 14, 2014 at 08:43:25PM +0100, Reimar Döffinger wrote:
> > On Fri, Nov 14, 2014 at 08:37:47PM +0100, Reimar Döffinger wrote:
> > > On Fri, Nov 14, 2014 at 03:19:26PM +0100, bzk0711 at aol.com wrote:
> > > > Dear ffmpeg developers,
> > > > 
> > > > is there any (planned) support for the Hap video codec in ffmpeg?
> > > > 
> > > > https://github.com/vidvox/hap
> > > > 
> > > > The implementation for Windows and Mac is available freely under a
> > > > permissive license.
> > > 
> > > Where is the actual source of these implementations?
> > > Above repository only contains some "boilerplate" wrapper, it lacks
> > > the core part: DXT (texture compression format) compressor/decompressor
> > > and is of very little value on its own.
> > 
> > Seems it should be possible to use https://code.google.com/p/libsquish/,
> > though unfortunately it is C++ code.

Just using OpenGL drivers might give simple code, though it won't be
regression-testable properly:
https://www.opengl.org/sdk/docs/man3/xhtml/glGetCompressedTexImage.xml

> Are you sure this compression format makes any sense whatsoever?
> You get a 1:6 compression (exactly, compared to RGB888), but
> also horrible compression artefacts.
> Simply going to half the resolution in x and y with YUV420 gives
> you 1:8 compression and I would bet it would even look better.
> At least I have a hard time seeing how it could look much worse.

Looking at texture compression formats, I don't think any make much
sense for video that is originally in 4:2:0 format.
The first that might be interesting (but is limited to a few mobile
devices) is ASTC.
Besides better quality at same bitrate, it allow for (relatively)
fine-grained per-frame compression ratio selection (and thus a
kind of rate-control), enough encoding options for perceptual encoding
and temporal compression (by using 3D textures).
But even with those improvements the usefulness for video even
compared to uncompressed seems questionable, especially since even
with uncompressed textures you could implement delta encoding
on the GPU.