[FFmpeg-devel] [PATCH] lavc/vvc: Invalidate PPSs which refer to a changed SPS

[Frank Plowman]

When the SPS associated with a particular SPS ID changes, invalidate all
the PPSs which use that SPS ID.  Fixes crashes with illegal bitstreams.
This is done in the CBS, rather than in libavcodec/vvc/ps.c like the SPS
ID reuse validation, as parts of the CBS parsing process for PPSs
depend on the SPS being referred to.

Signed-off-by: Frank Plowman <post at frankplowman.com>
---
 libavcodec/cbs_h2645.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
index c5f167334d..e2389f124e 100644
--- a/libavcodec/cbs_h2645.c
+++ b/libavcodec/cbs_h2645.c
@@ -789,9 +789,28 @@ static int cbs_h26 ## h26n ## _replace_ ## ps_var(CodedBitstreamContext *ctx, \
 }
 
 cbs_h266_replace_ps(6, VPS, vps, vps_video_parameter_set_id)
-cbs_h266_replace_ps(6, SPS, sps, sps_seq_parameter_set_id)
 cbs_h266_replace_ps(6, PPS, pps, pps_pic_parameter_set_id)
 
+static int cbs_h266_replace_sps(CodedBitstreamContext *ctx,
+                                CodedBitstreamUnit *unit)
+{
+    CodedBitstreamH266Context *priv = ctx->priv_data;
+    H266RawSPS *sps = unit->content;
+    unsigned int id = sps->sps_seq_parameter_set_id;
+    int err = ff_cbs_make_unit_refcounted(ctx, unit);
+    if (err < 0)
+        return err;
+    av_assert0(unit->content_ref);
+    if (priv->sps[id] && memcmp(priv->sps[id], unit->content_ref, sizeof(*priv->sps[id]))) {
+        for (unsigned int i = 0; i < VVC_MAX_PPS_COUNT; i++) {
+            if (priv->pps[i] && priv->pps[i]->pps_seq_parameter_set_id == id)
+                ff_refstruct_unref(&priv->pps[i]);
+        }
+    }
+    ff_refstruct_replace(&priv->sps[id], unit->content_ref);
+    return 0;
+}
+
 static int cbs_h266_replace_ph(CodedBitstreamContext *ctx,
                                CodedBitstreamUnit *unit,
                                H266RawPictureHeader *ph)
-- 
2.45.1