[FFmpeg-devel] [PATCH 1/3] avutil: Add Dolby Vision RPU side data type

[Jan Ekström]

On Thu, Oct 21, 2021 at 4:49 PM Derek Buitenhuis
<derek.buitenhuis at gmail.com> wrote:
>
> Signed-off-by: Derek Buitenhuis <derek.buitenhuis at gmail.com>
> ---
> All known encoders, etc. expect RPUs in this format, to my knowledge.
> (There is no spec for parsing the RPUs, even privately, and not a single
> piece of software that would benefit from that

DoVi Profile 5 and 7 rendering requires the data within these RPU
entities, AFAIK (as it contains various values to correctly configure
the custom color space). So software such as libplacebo where haasn
has made efforts towards implementing the non-standard color space
utilized would benefit from having the contents.

So while there clearly are two separate use cases, I would note that
saying "nothing would see any use from the bytes within these
structures" is maybe a bit disingenuous.

The two use cases being:
1. Just re-encoding the content. The contents of these RPU buffers
being unrelated and only passthrough is necessary.
2. Trying to gather the information of these metadata units regarding
interpretation of the received image.

Both are clearly valid use cases, and we should IMHO support both, at
least on the AVFrame level. Not that I mean that you should implement
the parsing of these metadata units, since it is clear you want to
keep away from that part of the work :) .

> - and it is a legal minefield
> which I am not going to touch.)

While with this I agree with completely. Or at least given the D
company's track record :P . That said, just parsing the metadata units
is probably much less of a swamp than actually trying to utilize the
metadata to properly render Profile 5 or 7 video.

For the record, there are at least two known to me OSS implementations
of RPU parsing/writing, one being made in Java and the other being
made in Rust.

Jan