WebRTC: Fix NACK recovered packets not being added to receive queue. v7.0.78 (#4467)

Fixes a bug in WebRTC NACK packet recovery mechanism where recovered
packets were being discarded instead of processed.

In `SrsRtcRecvTrack::on_nack()`, when a retransmitted packet arrived
(found in NACK receiver), the method would:
1. ✅ Remove the packet from NACK receiver (correct)
2. ❌ Return early without adding the packet to RTP queue (BUG)

This caused recovered packets to be lost, defeating the purpose of the
NACK mechanism and potentially causing media quality issues.

Restructured the control flow in `on_nack()` to ensure both new and
recovered packets reach the packet insertion logic:

- **Before**: Early return for recovered packets → packets discarded
- **After**: Conditional NACK management + unified packet processing →
all packets queued

Closes #3820

---------

Co-authored-by: Haibo Chen <[email protected]>
Co-authored-by: OSSRS-AI <[email protected]>

Author: 3 people

trunk/configure

@@ -50,7 +50,6 @@ if [[ $SRS_GENERATE_OBJS == YES ]]; then exit 0; fi
 #####################################################################################
 # ubuntu echo in Makefile cannot display color, use bash instead
 SRS_BUILD_SUMMARY="_srs_build_summary.sh"
-
 # utest make entry, (cd utest; make)
 SrsUtestMakeEntry="@echo -e \"ignore utest for it's disabled\""
 if [[ $SRS_UTEST == YES ]]; then SrsUtestMakeEntry="\$(MAKE)\$(JOBS) -C ${SRS_OBJS}/${SRS_PLATFORM}/utest"; fi
@@ -379,7 +378,7 @@ if [[ $SRS_UTEST == YES ]]; then
         "srs_utest_mp4" "srs_utest_service" "srs_utest_app" "srs_utest_rtc" "srs_utest_config2"
         "srs_utest_protocol" "srs_utest_protocol2" "srs_utest_kernel2" "srs_utest_protocol3"
         "srs_utest_st" "srs_utest_rtc2" "srs_utest_rtc3" "srs_utest_fmp4" "srs_utest_source_lock"
-        "srs_utest_stream_token")
+        "srs_utest_stream_token" "srs_utest_rtc_recv_track")
     # Always include SRT utest
     MODULE_FILES+=("srs_utest_srt")
     if [[ $SRS_GB28181 == YES ]]; then

trunk/doc/CHANGELOG.md

@@ -7,6 +7,7 @@ The changelog for SRS.
 <a name="v7-changes"></a>
 
 ## SRS 7.0 Changelog
+* v7.0, 2025-09-04, Merge [#4467](https://github.com/ossrs/srs/pull/4467): WebRTC: Fix NACK recovered packets not being added to receive queue. v7.0.78 (#4467)
 * v7.0, 2025-09-03, Merge [#4469](https://github.com/ossrs/srs/pull/4469): Upgrade HTTP parser from http-parser to llhttp. v7.0.77 (#4469)
 * v7.0, 2025-09-03, Merge [#4470](https://github.com/ossrs/srs/pull/4470): RTX: Fix race condition for timer. v7.0.76 (#4470)
 * v7.0, 2025-09-02, Merge [#4466](https://github.com/ossrs/srs/pull/4466): AI: GB28181: Remove embedded SIP server and enforce external SIP usage. v7.0.75 (#4466)

trunk/src/app/srs_app_rtc_source.cpp

@@ -3168,24 +3168,26 @@ srs_error_t SrsRtcRecvTrack::on_nack(SrsRtpPacket **ppkt)
     SrsRtpPacket *pkt = *ppkt;
     uint16_t seq = pkt->header.get_sequence();
     SrsRtpNackInfo *nack_info = nack_receiver_->find(seq);
+
     if (nack_info) {
         // seq had been received.
         nack_receiver_->remove(seq);
 #ifdef SRS_NACK_DEBUG_DROP_ENABLED
         srs_trace("NACK: recovered seq=%u", seq);
 #endif
-        return err;
-    }
-
-    // insert check nack list
-    uint16_t nack_first = 0, nack_last = 0;
-    if (!rtp_queue_->update(seq, nack_first, nack_last)) {
-        srs_warn("NACK: too old seq %u, range [%u, %u]", seq, rtp_queue_->begin, rtp_queue_->end);
-    }
-    if (srs_rtp_seq_distance(nack_first, nack_last) > 0) {
-        srs_trace("NACK: update seq=%u, nack range [%u, %u]", seq, nack_first, nack_last);
-        nack_receiver_->insert(nack_first, nack_last);
-        nack_receiver_->check_queue_size();
+    } else {
+        // insert check nack list
+        uint16_t nack_first = 0, nack_last = 0;
+        if (!rtp_queue_->update(seq, nack_first, nack_last)) {
+            srs_warn("NACK: too old seq %u, range [%u, %u]", seq, rtp_queue_->begin,
+                     rtp_queue_->end);
+        }
+        if (srs_rtp_seq_distance(nack_first, nack_last) > 0) {
+            srs_trace("NACK: update seq=%u, nack range [%u, %u]", seq, nack_first,
+                      nack_last);
+            nack_receiver_->insert(nack_first, nack_last);
+            nack_receiver_->check_queue_size();
+        }
     }
 
     // insert into video_queue and audio_queue

trunk/src/core/srs_core_version7.hpp

@@ -9,6 +9,6 @@
 
 #define VERSION_MAJOR 7
 #define VERSION_MINOR 0
-#define VERSION_REVISION 77
+#define VERSION_REVISION 78
 
 #endif