rtmp播放时，取相对时间戳逻辑确保时间戳同步

src/Common/Stamp.cpp

@@ -42,7 +42,40 @@ void Stamp::setPlayBack(bool playback) {
     _playback = playback;
 }
 
+void Stamp::makeRelation(Stamp &other){
+    _related = &other;
+}
+
 void Stamp::revise(int64_t dts, int64_t pts, int64_t &dts_out, int64_t &pts_out,bool modifyStamp) {
+    revise_l(dts,pts,dts_out,pts_out,modifyStamp);
+    if(modifyStamp || _playback){
+        //自动生成时间戳或回放，不需要做音视频同步
+        return;
+    }
+
+    if(_related && _related->_last_dts){
+        //音视频dts当前时间差
+        int64_t dts_diff = _last_dts - _related->_last_dts;
+        if(ABS(dts_diff) < 5000){
+            //如果绝对时间戳小于5秒，那么说明他们的起始时间戳是一致的，那么强制同步
+            _last_relativeStamp = _relativeStamp;
+            _relativeStamp = _related->_relativeStamp + dts_diff;
+            dts_out += dts_diff;
+            pts_out += dts_diff;
+//            DebugL << "音视频同步事件差:" << dts_diff;
+        }
+        //下次不用再强制同步
+        _related = nullptr;
+    }
+
+    if(dts_out < 0){
+        //相对时间戳小于0，那么说明是同步时间戳导致的,在这个过渡期内，我们一直返回上次的结果(目的是为了防止时间戳回退)
+        pts_out = _last_relativeStamp + (pts_out - dts_out);
+        dts_out = _last_relativeStamp;
+    }
+}
+
+void Stamp::revise_l(int64_t dts, int64_t pts, int64_t &dts_out, int64_t &pts_out,bool modifyStamp) {
     if(!pts){
         //没有播放时间戳,使其赋值为解码时间戳
         pts = dts;
@@ -53,6 +86,7 @@ void Stamp::revise(int64_t dts, int64_t pts, int64_t &dts_out, int64_t &pts_out,
         dts_out = dts;
         pts_out = pts;
         _relativeStamp = dts_out;
+        _last_dts = dts;
         return;
     }
 
@@ -62,6 +96,7 @@ void Stamp::revise(int64_t dts, int64_t pts, int64_t &dts_out, int64_t &pts_out,
     if(_last_dts != dts){
         //时间戳发生变更
         if(modifyStamp){
+            //内部自己生产时间戳
             _relativeStamp = _ticker.elapsedTime();
         }else{
             _relativeStamp += deltaStamp(dts);

src/Common/Stamp.h

@@ -32,6 +32,7 @@ public:
 private:
     int64_t _last_stamp = 0;
 };
+
 //该类解决时间戳回环、回退问题
 //计算相对时间戳或者产生平滑时间戳
 class Stamp : public DeltaStamp{
@@ -66,14 +67,25 @@ public:
      * @param playback 是否为回放模式
      */
     void setPlayBack(bool playback = true);
+
+    /**
+     * 产生关联,用于音视频同步用
+     */
+    void makeRelation(Stamp &other);
+
+private:
+    void revise_l(int64_t dts, int64_t pts, int64_t &dts_out, int64_t &pts_out,bool modifyStamp = false);
 private:
     int64_t _relativeStamp = 0;
-    int64_t _last_dts = -1;
+    int64_t _last_relativeStamp = 0;
+    int64_t _last_dts = 0;
     SmoothTicker _ticker;
     bool _playback = false;
+    Stamp *_related = nullptr;
 };
 
-
+//dts生成器，
+//pts排序后就是dts
 class DtsGenerator{
 public:
     DtsGenerator() = default;
@@ -90,8 +102,6 @@ private:
     int _sorter_max_size = 0;
     int _count_sorter_max_size = 0;
     set<uint32_t> _pts_sorter;
-
-
 };
 
 }//namespace mediakit

src/Rtmp/FlvMuxer.cpp

@@ -50,6 +50,9 @@ void FlvMuxer::start(const EventPoller::Ptr &poller,const RtmpMediaSource::Ptr &
         }
         strongSelf->onDetach();
     });
+
+    //音频同步于视频
+    _stamp[0].makeRelation( _stamp[1]);
     _ring_reader->setReadCB([weakSelf](const RtmpMediaSource::RingDataType &pkt){
         auto strongSelf = weakSelf.lock();
         if(!strongSelf){

src/Rtmp/RtmpSession.cpp

@@ -266,6 +266,8 @@ void RtmpSession::sendPlayResponse(const string &err,const RtmpMediaSource::Ptr
         onSendMedia(pkt);
     });
 
+    //音频同步于视频
+    _stamp[0].makeRelation( _stamp[1]);
     _pRingReader = src->getRing()->attach(getPoller());
     weak_ptr<RtmpSession> weakSelf = dynamic_pointer_cast<RtmpSession>(shared_from_this());
     _pRingReader->setReadCB([weakSelf](const RtmpMediaSource::RingDataType &pkt) {