flvdec: Don't export metadata entries that aren't proper metadata

This avoids writing these entries doubly if transcoding from
flv to flv, since the muxer blindly writes any and all metadata
keys set, in addition to the fixed fields that the muxer
always writes.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/flvdec.c

@@ -296,6 +296,20 @@ static int amf_parse_object(AVFormatContext *s, AVStream *astream, AVStream *vst
                 acodec->bit_rate = num_val * 1024.0;
         }
 
+        if (!strcmp(key, "duration")        ||
+            !strcmp(key, "filesize")        ||
+            !strcmp(key, "width")           ||
+            !strcmp(key, "height")          ||
+            !strcmp(key, "videodatarate")   ||
+            !strcmp(key, "framerate")       ||
+            !strcmp(key, "videocodecid")    ||
+            !strcmp(key, "audiodatarate")   ||
+            !strcmp(key, "audiosamplerate") ||
+            !strcmp(key, "audiosamplesize") ||
+            !strcmp(key, "stereo")          ||
+            !strcmp(key, "audiocodecid"))
+            return 0;
+
         if(amf_type == AMF_DATA_TYPE_BOOL) {
             av_strlcpy(str_val, num_val > 0 ? "true" : "false", sizeof(str_val));
             av_dict_set(&s->metadata, key, str_val, 0);