[FFmpeg-devel] [PATCH 3/3] avcodec: Implement mpeg4 nvdec hwaccel

Philip Langdale philipl at overt.org
Tue Nov 21 06:10:36 EET 2017

Hash: SHA1

On Mon, 20 Nov 2017 22:53:00 +0100
Michael Niedermayer <michael at niedermayer.cc> wrote:

> On Sun, Nov 19, 2017 at 11:52:28AM -0800, Philip Langdale wrote:
> > This was predictably nightmarish, given how ridiculous mpeg4 is.
> > I had to stare at the cuvid parser output for a long time to work
> > out what each field was supposed to be, and even then, I still don't
> > fully understand some of them, particularly:
> > 
> > vop_coded: I think this means whether the vop has a picture shape,
> >            and therefore a picture type. I have no samples where
> >            this is not the case.
> > divx_flags: There's obviously no documentation on what the possible
> >             flags are. I simply observed that this is '0' for a
> >             normal bitstream and '5' for packed b-frames.  
> > gmc_enabled: This seems to map to mc_sel being non-zero, but I also
> >              have no samples where that is true.  
> issues/388/Matrix.Reloaded.Trailer-640x346-XviD-1.0beta2-HE_AAC_subtitled.mkv
> seems to use gmc, didnt check how compex or trivial its use is
> [...]

I think it's as complex as you can get, and the nvidia decoder cannot
handle it properly. With vdpau, cuvid and now nvdec, there are a lot of
visual glitches. Interestingly, the resutls with nvdec are better than
cuvid, so not using the nvidia parser somehow makes things less worse.

I'd love to try a single warp point sample but can't find or generate

- --phil


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