avformat/utils: Slightly un-clutter code in determinable_frame_size() by using a switch

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/utils.c

@@ -894,12 +894,13 @@ int ff_read_packet(AVFormatContext *s, AVPacket *pkt)
 
 static int determinable_frame_size(AVCodecContext *avctx)
 {
-    if (/*avctx->codec_id == AV_CODEC_ID_AAC ||*/
-        avctx->codec_id == AV_CODEC_ID_MP1 ||
-        avctx->codec_id == AV_CODEC_ID_MP2 ||
-        avctx->codec_id == AV_CODEC_ID_MP3/* ||
-        avctx->codec_id == AV_CODEC_ID_CELT*/)
+    switch(avctx->codec_id) {
+    case AV_CODEC_ID_MP1:
+    case AV_CODEC_ID_MP2:
+    case AV_CODEC_ID_MP3:
         return 1;
+    }
+
     return 0;
 }