On 03/02/2024 15:46, Nuo Mi wrote:
On Sat, Feb 3, 2024 at 9:54 PM Frank Plowman <p...@frankplowman.com> wrote:

On 02/02/2024 14:39, Nuo Mi wrote:
On Thu, Feb 1, 2024 at 10:01 PM <p...@frankplowman.com> wrote:

From: Frank Plowman <p...@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 <p...@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.

I wrote it like this so that the avpriv_report_missing_feature is where
the feature would need to be, helping readability and searchability.

We need to make changes to both the cbs and the decoder for subpic support.
pps_slice_map is not the first place.

There is nothing strictly missing in the CBS, only the derivation of NumSlicesInSub needs to be moved which is quite subtle; I think the putting the error in the parameter set parser is clearer.

How is the patch below as an alternative?

diff --git a/libavcodec/vvc/vvc_ps.c b/libavcodec/vvc/vvc_ps.c
index 2cf156b323..4ef8f9f9b9 100644
--- a/libavcodec/vvc/vvc_ps.c
+++ b/libavcodec/vvc/vvc_ps.c
@@ -413,13 +413,20 @@ static void pps_no_rect_slice(VVCPPS* pps)

 static int pps_slice_map(VVCPPS *pps)
 {
+    const H266RawPPS* r = pps->r;
+
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)
+    if (pps->r->pps_rect_slice_flag) {
+        if (r->pps_single_slice_per_subpic_flag) {
+ avpriv_report_missing_feature(NULL, "pps_single_slice_per_subpic_flag");
+            return AVERROR_PATCHWELCOME;
+        }
+
         pps_rect_slice(pps);
-    else
+    } else
         pps_no_rect_slice(pps);

     return 0;
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