lavc: add avcodec_get_type() for mapping codec_id -> type.

libavcodec/utils.c

@@ -1301,3 +1301,17 @@ int avcodec_thread_init(AVCodecContext *s, int thread_count)
     return ff_thread_init(s);
 }
 #endif
+
+enum AVMediaType avcodec_get_type(enum CodecID codec_id)
+{
+    if (codec_id <= CODEC_ID_NONE)
+        return AVMEDIA_TYPE_UNKNOWN;
+    else if (codec_id < CODEC_ID_FIRST_AUDIO)
+        return AVMEDIA_TYPE_VIDEO;
+    else if (codec_id < CODEC_ID_FIRST_SUBTITLE)
+        return AVMEDIA_TYPE_AUDIO;
+    else if (codec_id < CODEC_ID_FIRST_UNKNOWN)
+        return AVMEDIA_TYPE_SUBTITLE;
+
+    return AVMEDIA_TYPE_UNKNOWN;
+}