riff: add comment for g721,g723 codec tags

Signed-off-by: Piotr Bandurski <ami_stuff@o2.pl>

libavformat/riff.c

@@ -450,8 +450,8 @@ const AVCodecTag ff_codec_wav_tags[] = {
     { AV_CODEC_ID_AMR_NB,          0x0038 },  /* rogue format number */
     { AV_CODEC_ID_G723_1,          0x0042 },
     { AV_CODEC_ID_ADPCM_G726,      0x0045 },
-    { AV_CODEC_ID_ADPCM_G726,      0x0014 },
-    { AV_CODEC_ID_ADPCM_G726,      0x0040 },
+    { AV_CODEC_ID_ADPCM_G726,      0x0014 },  /* g723 Antex */
+    { AV_CODEC_ID_ADPCM_G726,      0x0040 },  /* g721 Antex */
     { AV_CODEC_ID_MP2,             0x0050 },
     { AV_CODEC_ID_MP3,             0x0055 },
     { AV_CODEC_ID_AMR_NB,          0x0057 },