VAAPI: do not run out of pictures

Fix for commit-id: 5240dc3b
The previous commit caused the vout to deplete its picture pool.

modules/codec/avcodec/video.c

@@ -754,8 +754,7 @@ picture_t *DecodeVideo( decoder_t *p_dec, block_t **pp_block )
         if( p_sys->p_va && p_sys->p_ff_pic->opaque )
         {
             p_pic = (picture_t *)p_sys->p_ff_pic->opaque;
-            if( p_pic->format.i_chroma != VLC_CODEC_VAAPI_SURFACE )
-                decoder_LinkPicture( p_dec, p_pic );
+            if( p_pic ) decoder_LinkPicture( p_dec, p_pic );
 
             /* Fill p_picture_t from AVVideoFrame and do chroma conversion
              * if needed */
@@ -1016,7 +1015,6 @@ static int ffmpeg_GetFrameBuf( struct AVCodecContext *p_context,
         if( p_pic && ( p_pic->format.i_chroma == VLC_CODEC_VAAPI_SURFACE ) )
         {
             p_ff_pic->opaque = (void*)p_pic;
-            decoder_LinkPicture( p_dec, p_pic );
             vlc_va_Put( p_sys->p_va, p_ff_pic, p_pic );
         }
         else
@@ -1157,7 +1155,7 @@ static void ffmpeg_ReleaseFrameBuf( struct AVCodecContext *p_context,
     if( p_sys->p_va )
     {
         picture_t *p_pic = (picture_t*)p_ff_pic->opaque;
-        if( p_pic && p_pic->format.i_chroma == VLC_CODEC_VAAPI_SURFACE )
+        if( p_pic )
            decoder_UnlinkPicture( p_dec, p_pic );
         else
             vlc_va_Release( p_sys->p_va, p_ff_pic );
@@ -1174,8 +1172,8 @@ static void ffmpeg_ReleaseFrameBuf( struct AVCodecContext *p_context,
     else
     {
         picture_t *p_pic = (picture_t*)p_ff_pic->opaque;
-
-        decoder_UnlinkPicture( p_dec, p_pic );
+        if( p_pic )
+            decoder_UnlinkPicture( p_dec, p_pic );
     }
     for( int i = 0; i < 4; i++ )
         p_ff_pic->data[i] = NULL;