On Sat, Apr 6, 2024 at 9:46 PM Frank Plowman <p...@frankplowman.com> wrote:
> Key line from the spec is:
>
> "All SPS NAL units with a particular value of sps_seq_parameter_set_id
> in a CVS shall have the same content."
>
> Prior to this patch, the VVC decoder's behaviour on encountering a
> duplicated SPS ID (within the entire bitstream, not restricted to
> a CVS) was simply to replace the entry in the SPS lookup table with the
> new data. Illegal bitstreams with multiple SPSs in the same CVS sharing
> an ID but differing elsewhere could cause all manner of issues.
>
> The patch tracks which SPS IDs have been used in the given CVS using the
> new sps_id_used field of VVCParamSets. If it encounters an SPS with an
> ID already in use and whose content differs from the previous SPS, it
> throws an AVERROR_INVALIDDATA.
>
> Signed-off-by: Frank Plowman <p...@frankplowman.com>
> ---
> Changes since v1:
> * Track which SPS IDs are in use using a bit field rather than a bool
> array.
> * Move sps_id_used to the end of VVCParamSets.
> * Style: remove blank line & add braces for clarity.
>
Pushed.
Thank you, Frank
>
> libavcodec/vvc/vvc_ps.c | 28 ++++++++++++++++++++--------
> libavcodec/vvc/vvc_ps.h | 2 ++
> 2 files changed, 22 insertions(+), 8 deletions(-)
>
> diff --git a/libavcodec/vvc/vvc_ps.c b/libavcodec/vvc/vvc_ps.c
> index 301fa16400..7e967180d2 100644
> --- a/libavcodec/vvc/vvc_ps.c
> +++ b/libavcodec/vvc/vvc_ps.c
> @@ -219,14 +219,22 @@ fail:
> return NULL;
> }
>
> -static int decode_sps(VVCParamSets *ps, const H266RawSPS *rsps, void
> *log_ctx)
> +static int decode_sps(VVCParamSets *ps, const H266RawSPS *rsps, void
> *log_ctx, int is_clvss)
> {
> const int sps_id = rsps->sps_seq_parameter_set_id;
> const VVCSPS *old_sps = ps->sps_list[sps_id];
> const VVCSPS *sps;
>
> - if (old_sps && old_sps->r == rsps)
> - return 0;
> + if (is_clvss) {
> + ps->sps_id_used = 0;
> + }
> +
> + if (old_sps) {
> + if (old_sps->r == rsps || !memcmp(old_sps->r, rsps,
> sizeof(*old_sps->r)))
> + return 0;
> + else if (ps->sps_id_used & (1 << sps_id))
> + return AVERROR_INVALIDDATA;
> + }
>
> sps = sps_alloc(rsps, log_ctx);
> if (!sps)
> @@ -234,6 +242,7 @@ static int decode_sps(VVCParamSets *ps, const
> H266RawSPS *rsps, void *log_ctx)
>
> ff_refstruct_unref(&ps->sps_list[sps_id]);
> ps->sps_list[sps_id] = sps;
> + ps->sps_id_used |= (1 << sps_id);
>
> return 0;
> }
> @@ -610,7 +619,7 @@ static int decode_pps(VVCParamSets *ps, const
> H266RawPPS *rpps)
> return ret;
> }
>
> -static int decode_ps(VVCParamSets *ps, const CodedBitstreamH266Context
> *h266, void *log_ctx)
> +static int decode_ps(VVCParamSets *ps, const CodedBitstreamH266Context
> *h266, void *log_ctx, int is_clvss)
> {
> const H266RawPictureHeader *ph = h266->ph;
> const H266RawPPS *rpps;
> @@ -628,7 +637,7 @@ static int decode_ps(VVCParamSets *ps, const
> CodedBitstreamH266Context *h266, vo
> if (!rsps)
> return AVERROR_INVALIDDATA;
>
> - ret = decode_sps(ps, rsps, log_ctx);
> + ret = decode_sps(ps, rsps, log_ctx, is_clvss);
> if (ret < 0)
> return ret;
>
> @@ -867,13 +876,16 @@ int ff_vvc_decode_frame_ps(VVCFrameParamSets *fps,
> struct VVCContext *s)
> int ret = 0;
> VVCParamSets *ps = &s->ps;
> const CodedBitstreamH266Context *h266 = s->cbc->priv_data;
> + int is_clvss;
> +
> + decode_recovery_flag(s);
> + is_clvss = IS_CLVSS(s);
>
> - ret = decode_ps(ps, h266, s->avctx);
> + ret = decode_ps(ps, h266, s->avctx, is_clvss);
> if (ret < 0)
> return ret;
>
> - decode_recovery_flag(s);
> - ret = decode_frame_ps(fps, ps, h266, s->poc_tid0, IS_CLVSS(s));
> + ret = decode_frame_ps(fps, ps, h266, s->poc_tid0, is_clvss);
> decode_recovery_poc(s, &fps->ph);
> return ret;
> }
> diff --git a/libavcodec/vvc/vvc_ps.h b/libavcodec/vvc/vvc_ps.h
> index f60d8b81c6..710673ebed 100644
> --- a/libavcodec/vvc/vvc_ps.h
> +++ b/libavcodec/vvc/vvc_ps.h
> @@ -214,6 +214,8 @@ typedef struct VVCParamSets {
> const VVCALF *alf_list[VVC_MAX_ALF_COUNT]; ///<
> RefStruct reference
> const H266RawAPS *lmcs_list[VVC_MAX_LMCS_COUNT]; ///<
> RefStruct reference
> const VVCScalingList *scaling_list[VVC_MAX_SL_COUNT]; ///<
> RefStruct reference
> + // Bit field of SPS IDs used in the current CVS
> + uint16_t sps_id_used;
> } VVCParamSets;
>
> typedef struct VVCFrameParamSets {
> --
> 2.44.0
>
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