From 7f081b417868f5215df4405a4b354256ec702e2b Mon Sep 17 00:00:00 2001
From: "jinxue.cgh" <jinxue.cgh@alibaba-inc.com>
Date: Wed, 23 Dec 2020 15:13:21 +0800
Subject: [PATCH] RTC: Refine TWCC from 200ms to 50ms

---
 trunk/src/app/srs_app_log.hpp      |  1 +
 trunk/src/app/srs_app_rtc_conn.cpp | 18 +++++++++++++++++-
 trunk/src/app/srs_app_rtc_conn.hpp |  1 +
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/trunk/src/app/srs_app_log.hpp b/trunk/src/app/srs_app_log.hpp
index 5ae58059a..e6b82c4eb 100644
--- a/trunk/src/app/srs_app_log.hpp
+++ b/trunk/src/app/srs_app_log.hpp
@@ -38,6 +38,7 @@
 #define TAG_DTLS_ALERT "DTLS_ALERT"
 #define TAG_DTLS_HANG "DTLS_HANG"
 #define TAG_RESOURCE_UNSUB "RESOURCE_UNSUB"
+#define TAG_LARGE_TIMER "LARGE_TIMER"
 
 // Use memory/disk cache and donot flush when write log.
 // it's ok to use it without config, which will log to console, and default trace level.
diff --git a/trunk/src/app/srs_app_rtc_conn.cpp b/trunk/src/app/srs_app_rtc_conn.cpp
index 36724d557..dc9b46fa6 100644
--- a/trunk/src/app/srs_app_rtc_conn.cpp
+++ b/trunk/src/app/srs_app_rtc_conn.cpp
@@ -59,6 +59,7 @@ using namespace std;
 #include <srs_protocol_utility.hpp>
 
 #define SRS_TICKID_RTCP 0
+#define SRS_TICKID_TWCC 2
 
 ISrsRtcTransport::ISrsRtcTransport()
 {
@@ -908,7 +909,7 @@ srs_error_t SrsRtcPlayStream::do_request_keyframe(uint32_t ssrc, SrsContextId ci
 
 SrsRtcPublishStream::SrsRtcPublishStream(SrsRtcConnection* session, const SrsContextId& cid)
 {
-    timer_ = new SrsHourGlass(this, 200 * SRS_UTIME_MILLISECONDS);
+    timer_ = new SrsHourGlass(this, 10 * SRS_UTIME_MILLISECONDS);
 
     cid_ = cid;
     is_started = false;
@@ -927,6 +928,7 @@ SrsRtcPublishStream::SrsRtcPublishStream(SrsRtcConnection* session, const SrsCon
     twcc_fb_count_ = 0;
     
     pli_worker_ = new SrsRtcPLIWorker(this);
+    last_time_send_twcc_ = 0;
 }
 
 SrsRtcPublishStream::~SrsRtcPublishStream()
@@ -1000,6 +1002,10 @@ srs_error_t SrsRtcPublishStream::start()
         return err;
     }
 
+    if ((err = timer_->tick(SRS_TICKID_TWCC, 50 * SRS_UTIME_MILLISECONDS)) != srs_success) {
+        return srs_error_wrap(err, "twcc tick");
+    }
+
     if ((err = timer_->tick(SRS_TICKID_RTCP, 200 * SRS_UTIME_MILLISECONDS)) != srs_success) {
         return srs_error_wrap(err, "rtcp tick");
     }
@@ -1297,6 +1303,14 @@ srs_error_t SrsRtcPublishStream::send_periodic_twcc()
 {
     srs_error_t err = srs_success;
 
+    if (last_time_send_twcc_) {
+        srs_utime_t duration = srs_duration(last_time_send_twcc_, srs_get_system_time());
+        if (duration > 80 * SRS_UTIME_MILLISECONDS) {
+            srs_warn2(TAG_LARGE_TIMER, "send_twcc interval exceeded  %dms > 100ms", srsu2msi(duration));
+        }
+    }
+    last_time_send_twcc_ = srs_get_system_time();
+
     if (!rtcp_twcc_.need_feedback()) {
         return err;
     }
@@ -1457,7 +1471,9 @@ srs_error_t SrsRtcPublishStream::notify(int type, srs_utime_t interval, srs_utim
             srs_warn("XR err %s", srs_error_desc(err).c_str());
             srs_freep(err);
         }
+    }
 
+    if (type == SRS_TICKID_TWCC) {
         // We should not depends on the received packet,
         // instead we should send feedback every Nms.
         if ((err = send_periodic_twcc()) != srs_success) {
diff --git a/trunk/src/app/srs_app_rtc_conn.hpp b/trunk/src/app/srs_app_rtc_conn.hpp
index 65509b7d0..e04c9671e 100644
--- a/trunk/src/app/srs_app_rtc_conn.hpp
+++ b/trunk/src/app/srs_app_rtc_conn.hpp
@@ -341,6 +341,7 @@ private:
     SrsRtcpTWCC rtcp_twcc_;
     SrsRtpExtensionTypes extension_types_;
     bool is_started;
+    srs_utime_t last_time_send_twcc_;
 public:
     SrsRtcPublishStream(SrsRtcConnection* session, const SrsContextId& cid);
     virtual ~SrsRtcPublishStream();