[FFmpeg-devel] [PATCH 1/3] avcodec/dovi_rpu: implement support for profile 10

[Niklas Haas]

On Mon, 04 Mar 2024 14:06:51 +0100 Andreas Rheinhardt <andreas.rheinhardt at outlook.com> wrote:
> Niklas Haas:
> > From: Niklas Haas <git at haasn.dev>
> > 
> > Instead of the nal_prefix, this profile inside wraps the RPU inside an
> > EMDF header, as specified in ETSI TS 102 366. This particular usage is
> > supposedly specified in ETSI TS 103 572, at least according to European
> > Patent EP 3 588 964 A1, but I could not find any references to DV RPUs
> > in the former.
> > 
> > It's worth pointing out that the EMDF container is not byte-aligned,
> > meaning that payloads are delivered at arbitrary byte boundaries. Hence
> > the reason for doing it inside ff_dovi_rpu_parse, which already uses
> > a bitstream reader, rather than splitting off the container in
> > a separate stage. (Plus, we hard-code the DV-specific payload ID)
> > 
> > Magic values were taken from a combination of the sources below, all of
> > which agree about what the specific EMDF header should look like. In
> > fact, they all hard-code a very *specific* header sequence, but I wanted
> > to go the extra mile and at least properly skip the variable fields
> > - even though the non-existent Dolby Vision specification probably
> > specifies that they all must be 0. This is probably overkill.
> > 
> > Validated and tested using sample files from the merge request linked
> > below.
> > 
> > Relevant links:
> > - https://www.etsi.org/deliver/etsi_ts/102300_102399/102366/01.04.01_60/ts_102366v010401p.pdf
> > - https://patentimages.storage.googleapis.com/8a/0b/da/28294acaed2182/EP3588964A1.pdf
> > - https://www.etsi.org/deliver/etsi_ts/103500_103599/103572/01.03.01_60/ts_103572v010301p.pdf
> > - https://github.com/rockchip-linux/mpp/blob/fdeb8c378b79d4b4ef80457e4431815de89dc417/mpp/codec/dec/av1/av1d_cbs.c#L2378
> > - https://github.com/elginsk8r/android_kernel_amlogic_linux-4.9/blob/23a4c38bf06ef34821e476a8edddbf9213712c8a/drivers/amlogic/media/enhancement/amdolby_vision/amdolby_vision.c#L5638
> > - https://gitlab.com/mbunkus/mkvtoolnix/-/merge_requests/2254
> > ---
> >  libavcodec/dovi_rpu.c | 68 +++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 65 insertions(+), 3 deletions(-)
> > 
> > diff --git a/libavcodec/dovi_rpu.c b/libavcodec/dovi_rpu.c
> > index a6b23f4dd11..c7cdd65a2f2 100644
> > --- a/libavcodec/dovi_rpu.c
> > +++ b/libavcodec/dovi_rpu.c
> > @@ -174,6 +174,18 @@ static inline int64_t get_se_coef(GetBitContext *gb, const AVDOVIRpuDataHeader *
> >      return 0; /* unreachable */
> >  }
> >  
> > +static inline unsigned get_variable_bits(GetBitContext *gb, int n)
> > +{
> > +    unsigned int value = get_bits(gb, n);
> > +    int read_more = get_bits1(gb);
> > +    while (read_more) {
> > +        value = (value + 1) << n;
> > +        value += get_bits(gb, n);
> 
> Using |= is more appropriate.
> 
> > +        read_more = get_bits1(gb);
> > +    };
> 
> The ';' is a null statement.

Fixed both, thanks.