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SdpOfferAnswerHandler: Significantly reduce audio impairment.

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It was found from Chrome tracing that worker packet progression in
https://webrtc.github.io/samples/src/content/peerconnection/negotiate-timing/
during renegotiation of 100 transceivers is hindered by a multi-hundred
millisecond Invoke from the signaling to the worker thread. This
causes audio impairment.

Fix this by splitting the single Invoke into a series of Invokes,
allowing packets received during the renegotiation to be processed
between the worker invocations.

Experimental data of negotiation from 1 to 100 video transceivers

WebRtcDistinctWorkerThread OFF, before change:
4415.60 milliseconds, audio impairment 29760
4216.00 milliseconds, audio impairment 25560
4298.40 milliseconds, audio impairment 25440

WebRtcDistinctWorkerThread OFF, after change:
4258.70 milliseconds, audio impairment 26280
4255.50 milliseconds, audio impairment 25920
4363.10 milliseconds, audio impairment 25200

WebRtcDistinctWorkerThread ON, before change:
4407.80 milliseconds, audio impairment 24840
4541.00 milliseconds, audio impairment 26160
4377.80 milliseconds, audio impairment 17040

WebRtcDistinctWorkerThread ON, after change:
4364.80 milliseconds, audio impairment 0
4174.30 milliseconds, audio impairment 0
4309.00 milliseconds, audio impairment 0

We should reconsider this split after lazy decoders and decoder stream
projects have shipped, see
- bugs.webrtc.org/12462
- crbug.com/1157227
- crbug.com/1187289

Bug: webrtc:12840, webrtc:12462, chromium:1157227, chromium:1187289
Change-Id: I8e3b3943bd76f09da74b457690799415335b51f5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/221103
Commit-Queue: Markus Handell <handellm@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34202}
This commit is contained in:
Markus Handell 2021-06-02 16:17:35 +02:00 committed by WebRTC LUCI CQ
parent 7444b19833
commit bd933ee29a
1 changed files with 16 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
pc/sdp_offer_answer.cc
View File

@ -4213,18 +4213,25 @@ RTCError SdpOfferAnswerHandler::PushdownMediaDescription(
channels.push_back(std::make_pair(channel, content_desc));
}
if (!channels.empty()) {
// This for-loop of invokes helps audio impairment during re-negotiations.
// One of the causes is that downstairs decoder creation is synchronous at the
// moment, and that a decoder is created for each codec listed in the SDP.
//
// TODO(bugs.webrtc.org/12840): consider merging the invokes again after
// these projects have shipped:
// - bugs.webrtc.org/12462
// - crbug.com/1157227
// - crbug.com/1187289
for (const auto& entry : channels) {
RTCError error =
pc_->worker_thread()->Invoke<RTCError>(RTC_FROM_HERE, [&]() {
std::string error;
for (const auto& entry : channels) {
bool success =
(source == cricket::CS_LOCAL)
? entry.first->SetLocalContent(entry.second, type, &error)
: entry.first->SetRemoteContent(entry.second, type, &error);
if (!success) {
LOG_AND_RETURN_ERROR(RTCErrorType::INVALID_PARAMETER, error);
}
bool success =
(source == cricket::CS_LOCAL)
? entry.first->SetLocalContent(entry.second, type, &error)
: entry.first->SetRemoteContent(entry.second, type, &error);
if (!success) {
LOG_AND_RETURN_ERROR(RTCErrorType::INVALID_PARAMETER, error);
}
return RTCError::OK();
});