Use time.Ticker in play-from-disk

time.Sleep is not precise, instead use a ticker.

Relates to golang/go#44343

Co-authored-by: Twometer <twometer@outlook.de>

examples/play-from-disk-renegotation/main.go

@@ -167,15 +167,18 @@ func writeVideoToTrack(t *webrtc.TrackLocalStaticSample) {
 
 	// Send our video file frame at a time. Pace our sending so we send it at the same speed it should be played back as.
 	// This isn't required since the video is timestamped, but we will such much higher loss if we send all at once.
-	sleepTime := time.Millisecond * time.Duration((float32(header.TimebaseNumerator)/float32(header.TimebaseDenominator))*1000)
-	for {
+	//
+	// It is important to use a time.Ticker instead of time.Sleep because
+	// * avoids accumulating skew, just calling time.Sleep didn't compensate for the time spent parsing the data
+	// * works around latency issues with Sleep (see https://github.com/golang/go/issues/44343)
+	ticker := time.NewTicker(time.Millisecond * time.Duration((float32(header.TimebaseNumerator)/float32(header.TimebaseDenominator))*1000))
+	for ; true; <-ticker.C {
 		frame, _, err := ivf.ParseNextFrame()
 		if err != nil {
 			fmt.Printf("Finish writing video track: %s ", err)
 			return
 		}
 
-		time.Sleep(sleepTime)
 		if err = t.WriteSample(media.Sample{Data: frame, Duration: time.Second}); err != nil {
 			fmt.Printf("Finish writing video track: %s ", err)
 			return

examples/play-from-disk/README.md

@@ -1,6 +1,8 @@
 # play-from-disk
 play-from-disk demonstrates how to send video and/or audio to your browser from files saved to disk.
 
+For an example of playing H264 from disk see [play-from-disk-h264](https://github.com/pion/example-webrtc-applications/tree/master/play-from-disk-h264)
+
 ## Instructions
 ### Create IVF named `output.ivf` that contains a VP8 track and/or `output.ogg` that contains a Opus track
 ```

examples/play-from-disk/main.go

@@ -17,8 +17,9 @@ import (
 )
 
 const (
-	audioFileName = "output.ogg"
-	videoFileName = "output.ivf"
+	audioFileName   = "output.ogg"
+	videoFileName   = "output.ivf"
+	oggPageDuration = time.Millisecond * 20
 )
 
 func main() {
@@ -93,8 +94,12 @@ func main() {
 
 			// Send our video file frame at a time. Pace our sending so we send it at the same speed it should be played back as.
 			// This isn't required since the video is timestamped, but we will such much higher loss if we send all at once.
-			sleepTime := time.Millisecond * time.Duration((float32(header.TimebaseNumerator)/float32(header.TimebaseDenominator))*1000)
-			for {
+			//
+			// It is important to use a time.Ticker instead of time.Sleep because
+			// * avoids accumulating skew, just calling time.Sleep didn't compensate for the time spent parsing the data
+			// * works around latency issues with Sleep (see https://github.com/golang/go/issues/44343)
+			ticker := time.NewTicker(time.Millisecond * time.Duration((float32(header.TimebaseNumerator)/float32(header.TimebaseDenominator))*1000))
+			for ; true; <-ticker.C {
 				frame, _, ivfErr := ivf.ParseNextFrame()
 				if ivfErr == io.EOF {
 					fmt.Printf("All video frames parsed and sent")
@@ -105,7 +110,6 @@ func main() {
 					panic(ivfErr)
 				}
 
-				time.Sleep(sleepTime)
 				if ivfErr = videoTrack.WriteSample(media.Sample{Data: frame, Duration: time.Second}); ivfErr != nil {
 					panic(ivfErr)
 				}
@@ -155,7 +159,12 @@ func main() {
 
 			// Keep track of last granule, the difference is the amount of samples in the buffer
 			var lastGranule uint64
-			for {
+
+			// It is important to use a time.Ticker instead of time.Sleep because
+			// * avoids accumulating skew, just calling time.Sleep didn't compensate for the time spent parsing the data
+			// * works around latency issues with Sleep (see https://github.com/golang/go/issues/44343)
+			ticker := time.NewTicker(oggPageDuration)
+			for ; true; <-ticker.C {
 				pageData, pageHeader, oggErr := ogg.ParseNextPage()
 				if oggErr == io.EOF {
 					fmt.Printf("All audio pages parsed and sent")
@@ -174,8 +183,6 @@ func main() {
 				if oggErr = audioTrack.WriteSample(media.Sample{Data: pageData, Duration: sampleDuration}); oggErr != nil {
 					panic(oggErr)
 				}
-
-				time.Sleep(sampleDuration)
 			}
 		}()
 	}