Add a new function av_codec_get_tag2().

av_codec_get_tag() may return 0 both in case a codec_tag was
found and if no codec_tag was found.
The new function does not have this ambiguity.

libavformat/avformat.h

@@ -1930,6 +1930,18 @@ enum AVCodecID av_codec_get_id(const struct AVCodecTag * const *tags, unsigned i
  */
 unsigned int av_codec_get_tag(const struct AVCodecTag * const *tags, enum AVCodecID id);
 
+/**
+ * Get the codec tag for the given codec id.
+ *
+ * @param tags list of supported codec_id - codec_tag pairs, as stored
+ * in AVInputFormat.codec_tag and AVOutputFormat.codec_tag
+ * @param id codec id that should be searched for in the list
+ * @param tag A pointer to the found tag
+ * @return 0 if id was not found in tags, > 0 if it was found
+ */
+int av_codec_get_tag2(const struct AVCodecTag * const *tags, enum AVCodecID id,
+                      unsigned int *tag);
+
 int av_find_default_stream_index(AVFormatContext *s);
 
 /**

libavformat/utils.c

@@ -2583,11 +2583,26 @@ enum AVCodecID ff_get_pcm_codec_id(int bps, int flt, int be, int sflags)
 }
 
 unsigned int av_codec_get_tag(const AVCodecTag * const *tags, enum AVCodecID id)
+{
+    unsigned int tag;
+    if (!av_codec_get_tag2(tags, id, &tag))
+        return 0;
+    return tag;
+}
+
+int av_codec_get_tag2(const AVCodecTag * const *tags, enum AVCodecID id,
+                      unsigned int *tag)
 {
     int i;
     for(i=0; tags && tags[i]; i++){
-        int tag= ff_codec_get_tag(tags[i], id);
+        const AVCodecTag *codec_tags = tags[i];
-        if(tag) return tag;
+        while (codec_tags->id != AV_CODEC_ID_NONE) {
+            if (codec_tags->id == id) {
+                *tag = codec_tags->tag;
+                return 1;
+            }
+            codec_tags++;
+        }
     }
     return 0;
 }

libavformat/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 54
-#define LIBAVFORMAT_VERSION_MINOR 60
+#define LIBAVFORMAT_VERSION_MINOR 61
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \