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

[Nuo Mi]

Hi James,
Thanks for the suggestion. Now the vvcdec decoder is workable. The md5 is
matched with the vvdecapp. I am working on the conformance test. Hope I can
send the patch later.
thanks


On Thu, Dec 17, 2020 at 4:56 AM James Almer <jamrial at gmail.com> wrote:

> On 12/15/2020 10:43 AM, Nuo Mi wrote:
> > 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.
>
> The parser is meant to look byte by byte until it has found enough data
> to complete an entire Access Unit worth of NALUs.
> See how hevc does it in
>
> https://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavcodec/hevc_parser.c;h=463d352055b971bdcc27a27b3fcd7aa4b609286e;hb=HEAD#l261
>
>
> Once the delimitation of an AU is found, then the resulting buffer can
> be parsed (In VVC's case, we want that to be done by CBS) and ultimately
> propagated so the generic demux code in libavformat can create complete
> packets.
>
> >
> >
> >>> 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
> >> _______________________________________________
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