generator: clean up time

generator/mpegts_generator.go

@@ -29,6 +29,8 @@ LICENSE
 package generator
 
 import (
+	"time"
+
 	"bitbucket.org/ausocean/av/mpegts"
 	"bitbucket.org/ausocean/av/pes"
 )
@@ -56,7 +58,8 @@ const (
 	pmtPid    = 4096
 	videoPid  = 256
 	streamID  = 0xe0
-	ptsOffset = 0.7
+	ptsOffset = 700 * time.Millisecond
+	ptsFreq   = 90000 // Hz
 	maxCC     = 0xf
 )
 
@@ -64,9 +67,9 @@ const (
 type tsGenerator struct {
 	outputChan     chan []byte
 	nalInputChan   chan []byte
-	currentPtsTime float64
-	currentPcrTime float64
-	fps            float64
+	currentPtsTime time.Duration
+	currentPcrTime time.Duration
+	frameInterval  time.Duration
 	continuity     map[int]byte
 	isGenerating   bool
 }
@@ -76,7 +79,7 @@ func NewTsGenerator(fps float64) (g *tsGenerator) {
 	return &tsGenerator{
 		outputChan:     make(chan []byte, 1),
 		nalInputChan:   make(chan []byte, 1),
-		fps:            fps,
+		frameInterval:  time.Duration(float64(time.Second) / fps),
 		currentPtsTime: ptsOffset,
 		continuity: map[int]byte{
 			patPid:   0,
@@ -164,15 +167,15 @@ func (g *tsGenerator) generate() {
 
 // pts retuns the next presentation timestamp.
 func (g *tsGenerator) pts() uint64 {
-	pts := uint64(g.currentPtsTime * 90000) // FIXME(kortschak): Name this magic number.
-	g.currentPtsTime += 1 / g.fps
+	pts := uint64(g.currentPtsTime.Seconds() * ptsFreq)
+	g.currentPtsTime += g.frameInterval
 	return pts
 }
 
 // pcr returns the next program clock reference.
 func (g *tsGenerator) pcr() uint64 {
-	pcr := uint64(g.currentPcrTime * 90000) // FIXME(kortschak): Name this magic number.
-	g.currentPcrTime += 1 / g.fps
+	pcr := uint64(g.currentPcrTime.Seconds() * ptsFreq)
+	g.currentPcrTime += g.frameInterval
 	return pcr
 }