avcodec: allocate more hardware surfaces for threaded decoding

The number of threads impacts the number of surfaces that should be
allocated by the HW acceleration backend. If not enough surfaces are
allocated, the VAAPI and DXVA modules returned the oldest surface
currently in used. This technique can cause many visual glitches with
some samples. The number of allocated surfaces now scales with the
number of threads used by avcodec.

Fix #9887
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

modules/codec/avcodec/dxva2.c

@@ -283,6 +283,8 @@ struct vlc_va_sys_t
     int          surface_height;
     vlc_fourcc_t surface_chroma;
 
+    int          thread_count;
+
     vlc_va_surface_t surface[VA_DXVA2_MAX_SURFACE_COUNT];
     LPDIRECT3DSURFACE9 hw_surface[VA_DXVA2_MAX_SURFACE_COUNT];
 };
@@ -541,6 +543,8 @@ static int Open(vlc_va_t *external, AVCodecContext *ctx,
         goto error;
     }
 
+    va->thread_count = ctx->thread_count;
+
     /* TODO print the hardware name/vendor for debugging purposes */
     external->description = DxDescribe(va);
     external->pix_fmt = PIX_FMT_DXVA2_VLD;
@@ -859,7 +863,7 @@ static int DxCreateVideoDecoder(vlc_va_dxva2_t *va,
     int surface_count;
     switch (codec_id) {
     case AV_CODEC_ID_H264:
-        surface_count = 16 + 1;
+        surface_count = 16 + va->thread_count + 2;
         break;
     default:
         surface_count = 2 + 1;

modules/codec/avcodec/vaapi.c

@@ -96,7 +96,7 @@ struct vlc_va_sys_t
 };
 
 /* */
-static int Open( vlc_va_t *va, int i_codec_id )
+static int Open( vlc_va_t *va, int i_codec_id, int i_thread_count )
 {
     vlc_va_sys_t *sys = calloc( 1, sizeof(*sys) );
     if ( unlikely(sys == NULL) )
@@ -129,8 +129,8 @@ static int Open( vlc_va_t *va, int i_codec_id )
         break;
     case AV_CODEC_ID_H264:
         i_profile = VAProfileH264High;
-        i_surface_count = 16+1;
-        break;
+        i_surface_count = 16 + i_thread_count + 2;
+        break;;
     default:
         return VLC_EGENERIC;
     }
@@ -552,7 +552,7 @@ static int Create( vlc_va_t *p_va, AVCodecContext *ctx,
 
     (void) fmt;
 
-    int err = Open( p_va, ctx->codec_id );
+    int err = Open( p_va, ctx->codec_id, ctx->thread_count );
     if( err )
         return err;