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Fix transport-wide CC feedback when simulcast SSRCs are missing #2908

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merged 3 commits into from
Mar 2, 2022
Merged

Fix transport-wide CC feedback when simulcast SSRCs are missing #2908

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0da3558
Transport-wide CC feedback reports no longer use an SSRC of zero if t…
OxleyS Mar 1, 2022
d94d283
Expanded the SSRC candidate list for TWCC feedback to all video mediu…
OxleyS Mar 2, 2022
198cb2b
Styling cleanup for peer SSRC selection for TWCC.
OxleyS Mar 2, 2022
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26 changes: 22 additions & 4 deletions src/ice.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3979,6 +3979,7 @@ static gboolean janus_ice_outgoing_transport_wide_cc_feedback(gpointer user_data
janus_ice_handle *handle = (janus_ice_handle *)user_data;
janus_ice_peerconnection *pc = handle->pc;

guint32 ssrc_peer = 0;
janus_ice_peerconnection_medium *medium = NULL;
if(pc) {
/* Find inbound video medium */
Expand All @@ -3989,14 +3990,31 @@ static gboolean janus_ice_outgoing_transport_wide_cc_feedback(gpointer user_data
while (g_hash_table_iter_next(&iter, NULL, &value)) {
janus_ice_peerconnection_medium *m = value;
if(m && m->type == JANUS_MEDIA_VIDEO && m->recv) {
medium = m;
break;
/* If a medium (or simulcast layer, if applicable) has not received data, its SSRC may be unknown. */
/* Pick the first valid SSRC we find across all considered mediums */
int i = 0;
for(i = 0; i < 3; i++) {
if(m->ssrc_peer[i] != 0)
break;
}

/* Stop if we found a valid SSRC/medium to use */
if(i < 3) {
ssrc_peer = m->ssrc_peer[i];
medium = m;
break;
}
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I think this could be simplified as

int i = 0;
for(i=0; i<3; i++) {
	if(m->ssrc_peer[i] > 0) {
		medium = m;
		ssrc_peer = m->ssrc_peer[i];
		break;
	}
}
if(medium && ssrc_peer)
	break;

as I feel the second check is a bit more "awkward" (and possibly error prone should we decide to increase the number of substreams in the future), and the whole block could be made more compact.

}
}
janus_mutex_unlock(&handle->mutex);
}

if(pc && pc->do_transport_wide_cc && medium) {
if(!medium) {
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Just as a small nit and personal preference in terms of code style, we typically use if(medium == NULL) for checks like that.

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I found instances of both styles in the code base and wasn't sure which to use. Is there a coding style document I could refer to in the future?

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You're 100% right, and apologies for the confusion: that's mainly because of the many contributions we've received so far (and of which I'm grateful for of course), where we haven't always enforced a specific code style. Unfortunately we don't have a reference for that, and I'm not really sure we'll prepare one: even @atoppi and I write things a bit differently 😆 These are small nits that can be ascribed to my excessive pedantry on the matter, so no need to concern too much on that!

JANUS_LOG(LOG_HUGE, "No medium with a valid peer SSRC found for transport-wide CC feedback\n");
return G_SOURCE_CONTINUE;
}

if(pc && pc->do_transport_wide_cc) {
/* Create a transport wide feedback message */
size_t size = 1300;
char rtcpbuf[1300];
Expand Down Expand Up @@ -4065,7 +4083,7 @@ static gboolean janus_ice_outgoing_transport_wide_cc_feedback(gpointer user_data
guint8 feedback_packet_count = pc->transport_wide_cc_feedback_count++;
/* Create RTCP packet */
int len = janus_rtcp_transport_wide_cc_feedback(rtcpbuf, size,
medium->ssrc, medium->ssrc_peer[0], feedback_packet_count, packets_to_process);
medium->ssrc, ssrc_peer, feedback_packet_count, packets_to_process);
/* Enqueue it, we'll send it later */
if(len > 0) {
janus_plugin_rtcp rtcp = { .mindex = medium->mindex, .video = TRUE, .buffer = rtcpbuf, .length = len };
Expand Down