[FFmpeg-devel] [PATCH] avcodec/av1: fixed an vaapi decoding corruption issue

[Ruijing Dong]

 [problem]
 When decoding an av1 bitstream, it shows image corruption
 in the middle of the bitstream around key frames.

 [analysis]
 In av1_spec.pdf page 38/669, there is a sentence below:

 if ( frame_type == KEY_FRAME && show_frame ) {
    for ( i = 0; i < NUM_REF_FRAMES; i++) {
       RefValid[ i ] = 0
       ......
    }
    ......
 }

 This shows that the condition of invalidating current
 DPB frames should be the coming frame_type is KEY_FRAME plus
 show_frame is equal to 1. Otherwise, some of the frames
 in sequence after KEY_FRAME still refer to the reference frames
 before KEY_FRAME, and if these before KEY_FRAME reference
 frames were invalidated, these frames could not find their
 reference frames, and it could cause image corruption.

 [solution]
 Add show_frame flag as another condition to co-determine
 when to invalidate DPB reference frames.

 Mesa fix is in https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19386

cc: Fei Wang <fei.w.wang at intel.com>
Signed-off-by: Ruijing Dong <ruijing.dong at amd.com>
---
 libavcodec/vaapi_av1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/vaapi_av1.c b/libavcodec/vaapi_av1.c
index 63374c31c9..d0339b2705 100644
--- a/libavcodec/vaapi_av1.c
+++ b/libavcodec/vaapi_av1.c
@@ -274,7 +274,7 @@ static int vaapi_av1_start_frame(AVCodecContext *avctx,
     };
 
     for (int i = 0; i < AV1_NUM_REF_FRAMES; i++) {
-        if (pic_param.pic_info_fields.bits.frame_type == AV1_FRAME_KEY)
+        if (pic_param.pic_info_fields.bits.frame_type == AV1_FRAME_KEY && frame_header->show_frame)
             pic_param.ref_frame_map[i] = VA_INVALID_ID;
         else
             pic_param.ref_frame_map[i] = ctx->ref_tab[i].valid ?
-- 
2.25.1