Re: [FFmpeg-devel] [PATCH 1/8] avdovi/dovi_rpudec: handle prev_vdr_rpu_id failures

[Niklas Haas <ffmpeg@haasn.xyz>]

On Sun, 09 Jun 2024 17:05:46 +0200 Niklas Haas <ffmpeg@haasn.xyz> wrote:
> From: Niklas Haas <git@haasn.dev>
> 
> According to the spec, missing previous VDR RPU IDs do not constitute an
> error, but we should instead fallback first to VDR RPU with ID 0, and
> failing that, synthesize "neutral" metadata.
> 
> That's nontrivial though as the resulting metadata will be dependent on
> other properties of the RPU, and this case is not hit in practice so
> I'll defer it to a rainy day.
> ---
>  libavcodec/dovi_rpudec.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/libavcodec/dovi_rpudec.c b/libavcodec/dovi_rpudec.c
> index 7c7eda9d09..d1dcc3a262 100644
> --- a/libavcodec/dovi_rpudec.c
> +++ b/libavcodec/dovi_rpudec.c
> @@ -444,7 +444,12 @@ int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size,
>      if (use_prev_vdr_rpu) {
>          int prev_vdr_rpu_id = get_ue_golomb_31(gb);
>          VALIDATE(prev_vdr_rpu_id, 0, DOVI_MAX_DM_ID);
> +        if (!s->vdr[prev_vdr_rpu_id])
> +            prev_vdr_rpu_id = 0;
>          if (!s->vdr[prev_vdr_rpu_id]) {
> +            /* FIXME: Technically, the spec says that in this case we should
> +             * synthesize "neutral" vdr metadata, but easier to just error
> +             * out as this corner case is not hit in practice */
>              av_log(s->logctx, AV_LOG_ERROR, "Unknown previous RPU ID: %u\n",
>                     prev_vdr_rpu_id);
>              goto fail;
> -- 
> 2.45.1
> 

Ping for review, otherwis will merge soon as it's a lot of relatively
low-hanging fruit that fixes current deviations with the spec.
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