avformat/matroskaenc: Hoist check out of loop

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/matroskaenc.c

@@ -1877,9 +1877,13 @@ static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,
 
         // look for a codec ID string specific to mkv to use,
         // if none are found, use AVI codes
-        if (par->codec_id != AV_CODEC_ID_RAWVIDEO || par->codec_tag) {
+        if (par->codec_id == AV_CODEC_ID_FFV1) {
+            /* FFV1 is actually supported natively in Matroska,
+             * yet we use the VfW way to mux it for compatibility
+             * with old demuxers. (FIXME: Are they really important?) */
+        } else if (par->codec_id != AV_CODEC_ID_RAWVIDEO || par->codec_tag) {
             for (j = 0; ff_mkv_codec_tags[j].id != AV_CODEC_ID_NONE; j++) {
-                if (ff_mkv_codec_tags[j].id == par->codec_id && par->codec_id != AV_CODEC_ID_FFV1) {
+                if (ff_mkv_codec_tags[j].id == par->codec_id) {
                     put_ebml_string(pb, MATROSKA_ID_CODECID, ff_mkv_codec_tags[j].str);
                     native_id = 1;
                     break;