ff_dovi_rpu_parse() and ff_dovi_rpu_generate() are a bit inconsistent in
that they expect different levels of encapsulation, due to the nature of
how this is handled in the context of different APIs. Clarify the status
quo. (And fix an incorrect reference to the RPU payload bytes as 'RBSP')
Despite the suggestive size limits, this metadata ID has nothing to do
with the VDR metadata ID used for the data mappings. Actually, the
specification leaves them wholly unexplained, other than acknowleding
their existence. Must be some secret dolby sauce. They're not even
involved in DM metadata compression, which is handled using an entirely
separate ID.
That leaves us with a lack of anything sensible to do with these IDs.
Since we unfortunately only expose one `dm_metadata_id` field to the
user, just ensure that they match; which appears to always be the case
in practice. If somebody ever hits this error, I would really much
rather like to see the triggering file.
When this is 0, the metadata is explicitly inferred to stated default
values from the spec, rather than inferred from the previous frame's
values.
Likewise, when encoding, instead of checking if the value changed since
the last frame, we need to check if it differs from the default.
This function takes a decoded AVDOVIMetadata struct and turns it back
into a binary RPU. Verified using existing tools, and matches the
bitstream in official reference files.
I decided to just roll the EMDF and NAL encapsulation into this function
because the end user will need to do it otherwise anyways.
We need to set up the configuration struct appropriately based on the
codec type, colorspace metadata, and presence/absence of an EL (though,
we currently don't support an EL).
When present, we use the signalled RPU data header to help infer (and
validate) the right values.
Behavior can be controlled by a new DOVIContext.enable flag.
To allow compiling the decoding objects without the encoding objects and
vice versa. Common helpers that users of both APIs need are put into the
shared dovi_rpu.c.
To allow internally re-using it for both the encoder and decoder.
This is based on HEVC only, H.264/AV1 use their own (hopefully correctly
signalled) profiles (and in particular, the AV1 decoders implicitly
default the correct profile in the absence of a configuration record).
And make it public.
For encoding, users may also be interested in the configured level and
compatibility ID. So generalize the dv_profile field and just expose the
whole configuration record.
This makes the already rather reductive ff_dovi_update_cfg() function
almost wholly redundant, since users can just directly assign
DOVIContext.cfg.
The Dolby Vision RPU contains a CRC32 to validate the payload against.
The implementation is CRC32/MPEG-2.
The CRC is only verified with the AV_EF_CRCCHECK flag.
Co-authored-by: quietvoid <tcChlisop0@gmail.com>
This ensures that `gb` in the following section is fully byte-aligned,
points at the start of the actual RPU, and ends on the CRC terminator.
This is important for both calculation of the CRC, as well as dovi
extension block parsing (which aligns to byte boundaries in various
places).
It avoids allocations and the corresponding error checks.
Also avoids casts and indirections.
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Based on a mixture of guesswork, partial documentation in patents, and
reverse engineering of real-world samples. Confirmed working for all the
samples I've thrown at it.
Contains some annoying machinery to persist these values in between
frames, which is needed in theory even though I've never actually seen a
sample that relies on it in practice. May or may not work.
Since the distinction matters greatly for parsing the color matrix
values, this includes a small helper function to guess the right profile
from the RPU itself in case the user has forgotten to forward the dovi
configuration record to the decoder. (Which in practice, only ffmpeg.c
and ffplay do..)
Notable omissions / deviations:
- CRC32 verification. This is based on the MPEG2 CRC32 type, which is
similar to IEEE CRC32 but apparently different in subtle enough ways
that I could not get it to pass verification no matter what parameters
I fed to av_crc. It's possible the code needs some changes.
- Linear interpolation support. Nothing documents this (beyond its
existence) and no samples use it, so impossible to implement.
- All of the extension metadata blocks, but these contain values that
seem largely congruent with ST2094, HDR10, or other existing forms of
side data, so I will defer parsing/attaching them to a future commit.
- The patent describes a mechanism for predicting coefficients from
previous RPUs, but the bit for the flag whether to use the
prediction deltas or signal entirely new coefficients does not seem to
be present in actual RPUs, so we ignore this subsystem entirely.
- In the patent's spec, the NLQ subsystem also loops over
num_nlq_pivots, but even in the patent the number is hard-coded to one
iteration rather than signalled. So we only store one set of coefs.
Heavily influenced by https://github.com/quietvoid/dovi_tool
Documentation drawn from US Patent 10,701,399 B2 and ETSI GS CCM 001
Signed-off-by: Niklas Haas <git@haasn.dev>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Niklas Haas
Andreas Rheinhardt