lavc: mark bitmap based subtitles codecs as such.

libavcodec/avcodec.h

@@ -540,6 +540,10 @@ typedef struct AVCodecDescriptor {
  * Codec supports lossless compression. Audio and video codecs only.
  */
 #define AV_CODEC_PROP_LOSSLESS      (1 << 2)
+/**
+ * Subtitle codec is bitmap based
+ */
+#define AV_CODEC_PROP_BITMAP_SUB    (1 << 16)
 
 #if FF_API_OLD_DECODE_AUDIO
 /* in bytes */

libavcodec/codec_desc.c

@@ -2371,12 +2371,14 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .type      = AVMEDIA_TYPE_SUBTITLE,
         .name      = "dvd_subtitle",
         .long_name = NULL_IF_CONFIG_SMALL("DVD subtitles"),
+        .props     = AV_CODEC_PROP_BITMAP_SUB,
     },
     {
         .id        = AV_CODEC_ID_DVB_SUBTITLE,
         .type      = AVMEDIA_TYPE_SUBTITLE,
         .name      = "dvb_subtitle",
         .long_name = NULL_IF_CONFIG_SMALL("DVB subtitles"),
+        .props     = AV_CODEC_PROP_BITMAP_SUB,
     },
     {
         .id        = AV_CODEC_ID_TEXT,
@@ -2389,6 +2391,7 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .type      = AVMEDIA_TYPE_SUBTITLE,
         .name      = "xsub",
         .long_name = NULL_IF_CONFIG_SMALL("XSUB"),
+        .props     = AV_CODEC_PROP_BITMAP_SUB,
     },
     {
         .id        = AV_CODEC_ID_SSA,
@@ -2407,6 +2410,7 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .type      = AVMEDIA_TYPE_SUBTITLE,
         .name      = "hdmv_pgs_subtitle",
         .long_name = NULL_IF_CONFIG_SMALL("HDMV Presentation Graphic Stream subtitles"),
+        .props     = AV_CODEC_PROP_BITMAP_SUB,
     },
     {
         .id        = AV_CODEC_ID_DVB_TELETEXT,

libavcodec/utils.c

@@ -1872,7 +1872,7 @@ int avcodec_decode_subtitle2(AVCodecContext *avctx, AVSubtitle *sub,
             sub->pts = av_rescale_q(avpkt->pts,
                                     avctx->pkt_timebase, AV_TIME_BASE_Q);
         ret = avctx->codec->decode(avctx, sub, got_sub_ptr, &tmp);
-        sub->format = sub->num_rects && sub->rects[0]->ass;
+        sub->format = !(avctx->codec_descriptor->props & AV_CODEC_PROP_BITMAP_SUB);
 
         avctx->pkt = NULL;
         if (did_split) {