From 7d1bfcefe954c0548a7506a77c34367ebb88feb5 Mon Sep 17 00:00:00 2001
From: Dan Kortschak <dan@kortschak.io>
Date: Sat, 18 Aug 2018 13:36:14 +0930
Subject: [PATCH] generator: merge PTS and PCR clocks

---
 generator/mpegts_generator.go | 50 +++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 20 deletions(-)

diff --git a/generator/mpegts_generator.go b/generator/mpegts_generator.go
index 58ebd077..1f31983a 100644
--- a/generator/mpegts_generator.go
+++ b/generator/mpegts_generator.go
@@ -65,22 +65,25 @@ const (
 
 // tsGenerator encapsulates properties of an mpegts generator.
 type tsGenerator struct {
-	outputChan     chan []byte
-	nalInputChan   chan []byte
-	currentPtsTime time.Duration
-	currentPcrTime time.Duration
-	frameInterval  time.Duration
-	continuity     map[int]byte
-	isGenerating   bool
+	outputChan   chan []byte
+	nalInputChan chan []byte
+
+	clock         time.Duration
+	frameInterval time.Duration
+	ptsOffset     time.Duration
+
+	continuity map[int]byte
 }
 
 // NewTsGenerator returns an instance of the tsGenerator struct
 func NewTsGenerator(fps float64) (g *tsGenerator) {
 	return &tsGenerator{
-		outputChan:     make(chan []byte, 1),
-		nalInputChan:   make(chan []byte, 1),
-		frameInterval:  time.Duration(float64(time.Second) / fps),
-		currentPtsTime: ptsOffset,
+		outputChan:   make(chan []byte, 1),
+		nalInputChan: make(chan []byte, 1),
+
+		frameInterval: time.Duration(float64(time.Second) / fps),
+		ptsOffset:     ptsOffset,
+
 		continuity: map[int]byte{
 			patPid:   0,
 			pmtPid:   0,
@@ -147,6 +150,7 @@ func (g *tsGenerator) generate() {
 					Payload: patTable,
 				}
 				g.outputChan <- patPkt.Bytes()
+
 				// Create pmt table
 				pmtPkt := mpegts.Packet{
 					PUSI:    pusi,
@@ -156,27 +160,33 @@ func (g *tsGenerator) generate() {
 					Payload: pmtTable,
 				}
 				g.outputChan <- pmtPkt.Bytes()
+
 				// If pusi then we need to gen a pcr
 				pkt.PCR = g.pcr()
+
+				g.tick()
+
 				pusi = false
 			}
+
 			g.outputChan <- pkt.Bytes()
 		}
 	}
 }
 
-// pts retuns the next presentation timestamp.
-func (g *tsGenerator) pts() uint64 {
-	pts := uint64(g.currentPtsTime.Seconds() * ptsFreq)
-	g.currentPtsTime += g.frameInterval
-	return pts
+// tick advances the clock one frame interval.
+func (g *tsGenerator) tick() {
+	g.clock += g.frameInterval
 }
 
-// pcr returns the next program clock reference.
+// pts retuns the current presentation timestamp.
+func (g *tsGenerator) pts() uint64 {
+	return uint64((g.clock + g.ptsOffset).Seconds() * ptsFreq)
+}
+
+// pcr returns the current program clock reference.
 func (g *tsGenerator) pcr() uint64 {
-	pcr := uint64(g.currentPcrTime.Seconds() * ptsFreq)
-	g.currentPcrTime += g.frameInterval
-	return pcr
+	return uint64(g.clock.Seconds() * ptsFreq)
 }
 
 // ccFor returns the next continuity counter for pid.