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

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Niklas Haas:
> From: Niklas Haas <git@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.

> +    return value;
> +}
> +
>  #define VALIDATE(VAR, MIN, MAX)                                                 \
>      do {                                                                        \
>          if (VAR < MIN || VAR > MAX) {                                           \
> @@ -200,9 +212,59 @@ int ff_dovi_rpu_parse(DOVIContext *s, const uint8_t *rpu, size_t rpu_size)
>      if ((ret = init_get_bits8(gb, rpu, rpu_size)) < 0)
>          return ret;
>  
> -    /* RPU header, common values */
> -    nal_prefix = get_bits(gb, 8);
> -    VALIDATE(nal_prefix, 25, 25);
> +    /* Container header */
> +    if (s->dv_profile == 10 /* dav1.10 */) {
> +        /* DV inside AV1 re-uses EMDF container, parse header */
> +        int emdf_version, key_id, emdf_payload_id, emdf_payload_size, smploffste;
> +        emdf_version = get_bits(gb, 2);
> +        if (emdf_version == 3)
> +            emdf_version += get_variable_bits(gb, 2);
> +        key_id = get_bits(gb, 3);
> +        if (key_id == 7)
> +            key_id += get_variable_bits(gb, 3);
> +        emdf_payload_id = get_bits(gb, 5);
> +        if (emdf_payload_id == 0x1F)
> +            emdf_payload_id += get_variable_bits(gb, 5);
> +
> +        /* Magic values taken from amlogic and rockchip drivers, and also
> +         * match values found in practice (and validated in hardware) */
> +        VALIDATE(key_id, 6, 6);
> +        VALIDATE(emdf_payload_id, 256, 256);
> +
> +        /* Note: In theory, there could be multiple payloads, and we should
> +         * skip over the unused payloads until we find the one we're interested
> +         * in. But this capability does not seem to be used in practice, so
> +         * the DV-specific usage of EMDF probably requires only one payload
> +         * per T.35 OBU */
> +
> +        /* Skip emdf_payload_config() */
> +        if ((smploffste = get_bits1(gb)))
> +            skip_bits(gb, 11 + 1);
> +        if (get_bits1(gb)) /* duratione */
> +            get_variable_bits(gb, 11);
> +        if (get_bits1(gb)) /* groupide */
> +            get_variable_bits(gb, 2);
> +        if (get_bits1(gb)) /* codecdatae */
> +            skip_bits(gb, 8);
> +        if (!get_bits1(gb)) { /* discard_unknown_payload */
> +            int payload_frame_aligned;
> +            if (!smploffste) {
> +                if ((payload_frame_aligned = get_bits1(gb)))
> +                    skip_bits(gb, 1 + 1);
> +            }
> +            if (smploffste || payload_frame_aligned)
> +                skip_bits(gb, 5 + 2);
> +        }
> +
> +        emdf_payload_size = get_variable_bits(gb, 8);
> +        if (emdf_payload_size * 8 > get_bits_left(gb))
> +            return AVERROR_INVALIDDATA;
> +    } else {
> +        nal_prefix = get_bits(gb, 8);
> +        VALIDATE(nal_prefix, 25, 25);
> +    }
> +
> +    /* RPU header */
>      rpu_type = get_bits(gb, 6);
>      if (rpu_type != 2) {
>          av_log(s->logctx, AV_LOG_WARNING, "Unrecognized RPU type "

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