Re: [FFmpeg-devel] [PATCH] lavc/vvc: Error pps_single_slice_per_subpic_flag

[Nuo Mi <nuomi2021@gmail.com>]

On Thu, Feb 1, 2024 at 10:01 PM <post@frankplowman.com> wrote:

> From: Frank Plowman <post@frankplowman.com>
>
> pps_single_slice_per_subpic_flag is not yet supported.  Support is WIP,
> but in the meantime throw an error when trying to decode a bitstream
> with it set, avoiding an out-of-bounds array access.
>
> Fixes: out-of-bounds array access for conformance bitstreams
> SUBPIC_C_ERICSSON_1, SUBPIC_D_ERICSSON_1, MNUT_A_Nokia_4 and
> MNUT_B_Nokia_3.
>
> Signed-off-by: Frank Plowman <post@frankplowman.com>
> ---
>  libavcodec/vvc/vvc_ps.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/libavcodec/vvc/vvc_ps.c b/libavcodec/vvc/vvc_ps.c
> index 2cf156b323..bd81d70e71 100644
> --- a/libavcodec/vvc/vvc_ps.c
> +++ b/libavcodec/vvc/vvc_ps.c
> @@ -381,11 +381,16 @@ static void pps_multi_tiles_slice(VVCPPS *pps, const
> int tile_idx, const int i,
>      }
>  }
>
> -static void pps_rect_slice(VVCPPS* pps)
> +static int pps_rect_slice(VVCPPS* pps)
>  {
>      const H266RawPPS* r = pps->r;
>      int tile_idx = 0, off = 0;
>
> +    if (r->pps_single_slice_per_subpic_flag) {
> +        avpriv_report_missing_feature(NULL,
> "pps_single_slice_per_subpic_flag");
> +        return AVERROR_PATCHWELCOME;
> +    }
> +
>      for (int i = 0; i < r->pps_num_slices_in_pic_minus1 + 1; i++) {
>          if (!r->pps_slice_width_in_tiles_minus1[i] &&
>              !r->pps_slice_height_in_tiles_minus1[i]) {
> @@ -396,9 +401,11 @@ static void pps_rect_slice(VVCPPS* pps)
>          }
>          tile_idx = next_tile_idx(tile_idx, i, r);
>      }
> +
> +    return 0;
>  }
>
> -static void pps_no_rect_slice(VVCPPS* pps)
> +static int pps_no_rect_slice(VVCPPS* pps)
>  {
>      const H266RawPPS* r = pps->r;
>      int ctu_x, ctu_y, off = 0;
> @@ -409,20 +416,24 @@ static void pps_no_rect_slice(VVCPPS* pps)
>              pps_add_ctus(pps, &off, ctu_x, ctu_y,
> r->col_width_val[tile_x], r->row_height_val[tile_y]);
>          }
>      }
> +
> +    return 0;
>  }
>
>  static int pps_slice_map(VVCPPS *pps)
>  {
> +    int ret;
> +
>      pps->ctb_addr_in_slice = av_calloc(pps->ctb_count,
> sizeof(*pps->ctb_addr_in_slice));
>      if (!pps->ctb_addr_in_slice)
>          return AVERROR(ENOMEM);
>
>      if (pps->r->pps_rect_slice_flag)
> -        pps_rect_slice(pps);
> +        ret = pps_rect_slice(pps);
>      else
> -        pps_no_rect_slice(pps);
> +        ret = pps_no_rect_slice(pps);
>
> -    return 0;
> +    return ret;
>  }
>
Thank you Frank. This changed  too much code.
How about we only check the sps_num_subpics_minus1 in decode_sps.

>
>  static void pps_ref_wraparound_offset(VVCPPS *pps, const VVCSPS *sps)
> --
> 2.43.0
>
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