res_pjsip_sdp_rtp.c: Fix native formats containing formats that were not negotiated.

Outgoing PJSIP calls can result in non-negotiated formats listed in the
channel's native formats if video formats are listed in the endpoint's
configuration.  The resulting call could then use a non-negotiated format
resulting in one way audio.

* Simplified the update of session->req_caps in set_caps().  Why do
something in five steps when only one is needed?

AFS-162 #close

Review: https://reviewboard.asterisk.org/r/4000/
........

Merged revisions 423561 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@423563 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_pjsip.c

@@ -417,6 +417,11 @@ static struct ast_channel *chan_pjsip_new(struct ast_sip_session *session, int s
 	}
 
 	ast_channel_nativeformats_set(chan, caps);
+
+	/*
+	 * XXX Probably should pick the first audio codec instead
+	 * of simply the first codec.  The first codec may be video.
+	 */
 	fmt = ast_format_cap_get_format(caps, 0);
 	ast_channel_set_writeformat(chan, fmt);
 	ast_channel_set_rawwriteformat(chan, fmt);

res/res_pjsip_sdp_rtp.c

@@ -256,18 +256,26 @@ static int set_caps(struct ast_sip_session *session, struct ast_sip_session_medi
 	ast_rtp_codecs_payloads_copy(&codecs, ast_rtp_instance_get_codecs(session_media->rtp),
 				     session_media->rtp);
 
-	ast_format_cap_remove_by_type(caps, AST_MEDIA_TYPE_UNKNOWN);
-	ast_format_cap_append_from_cap(caps, session->req_caps, AST_MEDIA_TYPE_UNKNOWN);
-	ast_format_cap_remove_by_type(caps, media_type);
-	ast_format_cap_append_from_cap(caps, joint, AST_MEDIA_TYPE_UNKNOWN);
-	ast_format_cap_append_from_cap(session->req_caps, caps, AST_MEDIA_TYPE_UNKNOWN);
+	ast_format_cap_append_from_cap(session->req_caps, joint, AST_MEDIA_TYPE_UNKNOWN);
 
 	if (session->channel) {
 		struct ast_format *fmt;
 
 		ast_channel_lock(session->channel);
+		ast_format_cap_remove_by_type(caps, AST_MEDIA_TYPE_UNKNOWN);
 		ast_format_cap_append_from_cap(caps, ast_channel_nativeformats(session->channel), AST_MEDIA_TYPE_UNKNOWN);
 		ast_format_cap_remove_by_type(caps, media_type);
+
+		/*
+		 * XXX Historically we picked the "best" joint format to use
+		 * and stuck with it.  It would be nice to just append the
+		 * determined joint media capabilities to give translation
+		 * more formats to choose from when necessary.  Unfortunately,
+		 * there are some areas of the system where this doesn't work
+		 * very well. (The softmix bridge in particular is reluctant
+		 * to pick higher fidelity formats and has a problem with
+		 * asymmetric sample rates.)
+		 */
 		fmt = ast_format_cap_get_format(joint, 0);
 		ast_format_cap_append(caps, fmt, 0);