[FFmpeg-devel] [PATCH 0/3] add vvc raw demuxer

[Nuo Mi]

On Tue, Dec 15, 2020 at 4:44 AM Mark Thompson <sw at jkqxz.net> wrote:

> On 14/12/2020 13:31, Nuo Mi wrote:
> > Hi Mark,
> > I have almost done the cbs for sps, pps, and slice header. I will start
> to
> > implement the parser.
>
> This looks fun :)
>
> > Few questions for you:
> > 1. We need over-read some nals to detect the frame boundaries. But those
> > nals may switch/replace sps/pps. Do we need to use an output cbs and get
> > frames from the output cbs?
>
> I'm not seeing where this can happen - if you see a new parameter set then
> you must be in a new AU so you don't parse it, while a new VCL NAL as part
> of a new frame with no PS before it must have a parsable header?  (Or am I
> missing some problematic case?)
>

> > 2. We can't handle an incompleted nal in current cbs.
> >
> https://github.com/FFmpeg/FFmpeg/blob/03c8fe49ea3f2a2444607e541dff15a1ccd7f0c2/libavcodec/h2645_parse.c#L437
> ,
> > do we have a plan to fix it? What's your suggstion for the frame split?
>
> I'm unsure what the question is.  You will always need to keep reading
> until you split a valid NAL unit which isn't in the current AU (noting that
> a slice is the last slice in the current frame is never sufficient, because
> suffixes might follow).
>
> I want to feed the input buffer to cbs and get nal units from it. Seems it
does not work like this.
We still need a frame split in the parser. And feed the entire frame to
cbs.


> > 3. How to well test the cbs?
>
> Passthrough is the best initial test, by making an h266_metadata bsf (even
> if it has no options).  The existing test coverage in FATE of CBS is
> primarily driven by this - for H.26[45], the input streams there are a
> subset of the H.26[45].1 conformance test streams chosen to cover as much
> of the header space as possible.
>
> I recommend enabling the write support ASAP (by adding the second include
> of cbs_h266_syntax_template.c), because the double build can shake out
> other problems too.
>
> My original plan is cbs->parser->vvdec decoder->60% comfornace passrate ->
check in -> h266_metadata.
are you suggest we implement h266_metadata firstly?

thanks

Thanks,
>
> - Mark
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".