--- channels/chan_sip.c	(Asterisk 11.20.0)
+++ channels/chan_sip.c	(working copy)
@@ -12698,6 +12698,2 @@
 		break;
-	case AST_FORMAT_ILBC:
-		/* Add information about us using only 20/30 ms packetization */
-		ast_str_append(a_buf, 0, "a=fmtp:%d mode=%d\r\n", rtp_code, fmt.cur_ms);
-		break;
 	case AST_FORMAT_SIREN7:
--- main/format.c	(Asterisk 11.20.0)
+++ main/format.c	(working copy)
@@ -1051,3 +1051,3 @@
 	format_list_add_static(ast_format_set(&tmpfmt, AST_FORMAT_SPEEX16, 0), "speex16", 16000, "SpeeX 16khz", 10, 10, 60, 10, 20, 0, 0);   /*!< codec_speex.c */
-	format_list_add_static(ast_format_set(&tmpfmt, AST_FORMAT_ILBC, 0), "ilbc", 8000, "iLBC", 50, 30, 30, 30, 30, 0, 0);                 /*!< codec_ilbc.c */ /* inc=30ms - workaround */
+	format_list_add_static(ast_format_set(&tmpfmt, AST_FORMAT_ILBC, 0), "ilbc", 8000, "iLBC", 50, 30, 300, 30, 30, 0, 0);                /*!< codec_ilbc.c */
 	format_list_add_static(ast_format_set(&tmpfmt, AST_FORMAT_G726_AAL2, 0), "g726aal2", 8000, "G.726 AAL2", 40, 10, 300, 10, 20, 0, 0); /*!< codec_g726.c */