pjsip: Extend 'asymmetric_rtp_codec' option to include us changing.

PJSIP support in Asterisk differs from chan_sip in that it
allows media to be sent as-is without transcoding provided
the codecs were negotiated in the SDP. This is allowed
according to the RFC. Support for this differs quite a lot
though and some endpoints do not handle it well.

This change extends the 'asymmetric_rtp_codec' option to
also cover this case. When set to no (the default) the code
behaves as chan_sip does - the best codec is selected and
we will only ever send that, unless we change what we are
sending if the remote side changes. When set to yes we
will send media as-is without transcoding if the codec
has been negotiated in the SDP.

ASTERISK-26996

Change-Id: Ib1647f6902a0843e8c435946f831c2159e8d1d51

diff --git a/CHANGES b/CHANGES
index 709d6c92ae66e67bfb13eaa2d664baeab6ec6e4a..05a34b437439a0e23f5a8870599055eab42f4d13 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -25,6 +25,12 @@ chan_pjsip
    function any contact which is considered unreachable due to qualify being
    enabled will no longer be called.
 
+ * The asymmetric_rtp_codec option now also controls whether chan_pjsip will
+   send media as-is without transcoding if the codec has been negotiated in the
+   SDP. If set to "no" then Asterisk will only ever send the preferred codec
+   from the SDP, unless the remote side sends a different codec and we will
+   switch to match.
+
 ------------------------------------------------------------------------------
 --- Functionality changes from Asterisk 14.4.0 to Asterisk 14.5.0 ------------
 ------------------------------------------------------------------------------

diff --git a/channels/chan_pjsip.c b/channels/chan_pjsip.c
index 851c9135a3486ef358732e6bf62471046038bb08..48778ef9de411f91e6adf7093b8d613eb1aed9d4 100644 (file)
--- a/channels/chan_pjsip.c
+++ b/channels/chan_pjsip.c
@@ -737,11 +737,24 @@ static struct ast_frame *chan_pjsip_read(struct ast_channel *ast)
 
        if (!session->endpoint->asymmetric_rtp_codec &&
                ast_format_cmp(ast_channel_rawwriteformat(ast), f->subclass.format) == AST_FORMAT_CMP_NOT_EQUAL) {
-               /* For maximum compatibility we ensure that the write format matches that of the received media */
+               struct ast_format_cap *caps;
+
+               /* For maximum compatibility we ensure that the formats match that of the received media */
                ast_debug(1, "Oooh, got a frame with format of %s on channel '%s' when we're sending '%s', switching to match\n",
                        ast_format_get_name(f->subclass.format), ast_channel_name(ast),
                        ast_format_get_name(ast_channel_rawwriteformat(ast)));
+
+               caps = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT);
+               if (caps) {
+                       ast_format_cap_append_from_cap(caps, ast_channel_nativeformats(ast), AST_MEDIA_TYPE_UNKNOWN);
+                       ast_format_cap_remove_by_type(caps, AST_MEDIA_TYPE_AUDIO);
+                       ast_format_cap_append(caps, f->subclass.format, 0);
+                       ast_channel_nativeformats_set(ast, caps);
+                       ao2_ref(caps, -1);
+               }
+
                ast_set_write_format_path(ast, ast_channel_writeformat(ast), f->subclass.format);
+               ast_set_read_format_path(ast, ast_channel_readformat(ast), f->subclass.format);
 
                if (ast_channel_is_bridged(ast)) {
                        ast_channel_set_unbridged_nolock(ast, 1);

diff --git a/res/res_pjsip_sdp_rtp.c b/res/res_pjsip_sdp_rtp.c
index 6f94b0f4ac118a3774e52e16cad4c0b28965f76f..5ae108f76feb7989e60274ea4a53ea19f65c3a11 100644 (file)
--- a/res/res_pjsip_sdp_rtp.c
+++ b/res/res_pjsip_sdp_rtp.c
@@ -411,7 +411,24 @@ static int set_caps(struct ast_sip_session *session,
                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);
-               ast_format_cap_append_from_cap(caps, joint, media_type);
+
+               /*
+                * If we don't allow the sending codec to be changed on our side
+                * then get the best codec from the joint capabilities of the media
+                * type and use only that. This ensures the core won't start sending
+                * out a format that we aren't currently sending.
+                */
+               if (!session->endpoint->asymmetric_rtp_codec) {
+                       struct ast_format *best;
+
+                       best = ast_format_cap_get_best_by_type(joint, media_type);
+                       if (best) {
+                               ast_format_cap_append(caps, best, ast_format_cap_get_framing(joint));
+                               ao2_ref(best, -1);
+                       }
+               } else {
+                       ast_format_cap_append_from_cap(caps, joint, media_type);
+               }
 
                /*
                 * Apply the new formats to the channel, potentially changing