乱序重排和B帧处理

common/dtsestimator.go

@@ -0,0 +1,52 @@
+package common
+
+// DTSEstimator is a DTS estimator.
+type DTSEstimator struct {
+	prevDTS     uint32
+	prevPTS     uint32
+	prevPrevPTS uint32
+	dts         func(uint32) uint32
+}
+
+func (d *DTSEstimator) _dts(pts uint32) uint32 {
+	// P or I frame
+	if pts > d.prevPTS {
+		// previous frame was B
+		// use the DTS of the previous frame
+		if d.prevPTS < d.prevPrevPTS {
+			return d.prevPTS
+		}
+
+		// previous frame was P or I
+		// use two frames ago plus a small quantity
+		// to avoid non-monotonous DTS with B-frames
+		return d.prevPrevPTS + 1
+	}
+
+	// B Frame
+	// increase by a small quantity
+	return d.prevDTS + 1
+}
+
+// NewDTSEstimator allocates a DTSEstimator.
+func NewDTSEstimator() *DTSEstimator {
+	result := &DTSEstimator{}
+	result.dts = func(pts uint32) uint32 {
+		if pts > 0 {
+			result.dts = result._dts
+		}
+		return pts
+	}
+	return result
+}
+
+// Feed provides PTS to the estimator, and returns the estimated DTS.
+func (d *DTSEstimator) Feed(pts uint32) uint32 {
+	dts := d.dts(pts)
+
+	d.prevPrevPTS = d.prevPTS
+	d.prevPTS = pts
+	d.prevDTS = dts
+
+	return dts
+}