--- movenc.c	2015-03-16 14:25:54.000000000 -0500
+++ movenc_amr.c	2015-03-20 11:01:44.000000000 -0500
@@ -1133,7 +1133,13 @@
     else if (track->enc->codec_id == AV_CODEC_ID_MOV_TEXT)  tag = MKTAG('t','x','3','g');
     else if (track->enc->codec_id == AV_CODEC_ID_VC1)       tag = MKTAG('v','c','-','1');
     else if (track->enc->codec_type == AVMEDIA_TYPE_VIDEO)  tag = MKTAG('m','p','4','v');
-    else if (track->enc->codec_type == AVMEDIA_TYPE_AUDIO)  tag = MKTAG('m','p','4','a');
+    else if (track->enc->codec_type == AVMEDIA_TYPE_AUDIO)
+    {
+      if (track->enc->codec_id == AV_CODEC_ID_AMR_NB)       tag = MKTAG('s','a','m','r');
+      else if (track->enc->codec_id == AV_CODEC_ID_AMR_WB)  tag = MKTAG('s','a','w','b');
+      else
+        tag = MKTAG('m','p','4','a');
+    }
     else if (track->enc->codec_id == AV_CODEC_ID_DVD_SUBTITLE)  tag = MKTAG('m','p','4','s');
 
     return tag;

--- isom.c	2015-03-16 14:25:54.000000000 -0500
+++ isom_amr.c	2015-03-20 10:59:44.000000000 -0500
@@ -64,6 +64,8 @@
     { AV_CODEC_ID_QCELP       , 0xE1 },
     { AV_CODEC_ID_MPEG4SYSTEMS, 0x01 },
     { AV_CODEC_ID_MPEG4SYSTEMS, 0x02 },
+    { AV_CODEC_ID_AMR_NB,          MKTAG('s', 'a', 'm', 'r') }, /* AMR-NB 3gp */
+    { AV_CODEC_ID_AMR_WB,          MKTAG('s', 'a', 'w', 'b') }, /* AMR-WB 3gp */
     { AV_CODEC_ID_NONE        ,    0 },
 };