muxer: fix discontinuity in part ID (#107)

(bluenviron/mediamtx#2317) this prevented Low-Latency HLS from running smoothly on Safari
bluenviron · Nov 10, 2023 · e7092f1 · e7092f1
1 parent 006854b
commit e7092f1
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Showing 4 changed files with 38 additions and 24 deletions.
diff --git a/muxer_segment_fmp4.go b/muxer_segment_fmp4.go
@@ -19,7 +19,8 @@ type muxerSegmentFMP4 struct {
 	audioTimeScale uint32
 	prefix         string
 	forceSwitched  bool
-	genPartID      func() uint64
+	takePartID     func() uint64
+	givePartID     func()
 	publishPart    func(*muxerPart)
 
 	name        string
@@ -42,7 +43,8 @@ func newMuxerSegmentFMP4(
 	prefix string,
 	forceSwitched bool,
 	factory storage.Factory,
-	genPartID func() uint64,
+	takePartID func() uint64,
+	givePartID func(),
 	publishPart func(*muxerPart),
 ) (*muxerSegmentFMP4, error) {
 	s := &muxerSegmentFMP4{
@@ -56,7 +58,8 @@ func newMuxerSegmentFMP4(
 		audioTimeScale: audioTimeScale,
 		prefix:         prefix,
 		forceSwitched:  forceSwitched,
-		genPartID:      genPartID,
+		takePartID:     takePartID,
+		givePartID:     givePartID,
 		publishPart:    publishPart,
 		name:           segmentName(prefix, id, true),
 	}
@@ -73,7 +76,7 @@ func newMuxerSegmentFMP4(
 		s.audioTrack,
 		s.audioTimeScale,
 		prefix,
-		s.genPartID(),
+		s.takePartID(),
 		s.storage.NewPart(),
 	)
 
@@ -111,9 +114,12 @@ func (s *muxerSegmentFMP4) finalize(nextDTS time.Duration) error {
 			return err
 		}
 
-		s.publishPart(s.currentPart)
 		s.parts = append(s.parts, s.currentPart)
+		s.publishPart(s.currentPart)
+	} else {
+		s.givePartID()
 	}
+
 	s.currentPart = nil
 
 	s.storage.Finalize()
@@ -153,7 +159,7 @@ func (s *muxerSegmentFMP4) writeVideo(
 			s.audioTrack,
 			s.audioTimeScale,
 			s.prefix,
-			s.genPartID(),
+			s.takePartID(),
 			s.storage.NewPart(),
 		)
 	}
@@ -191,7 +197,7 @@ func (s *muxerSegmentFMP4) writeAudio(
 			s.audioTrack,
 			s.audioTimeScale,
 			s.prefix,
-			s.genPartID(),
+			s.takePartID(),
 			s.storage.NewPart(),
 		)
 	}

diff --git a/muxer_segmenter_fmp4.go b/muxer_segmenter_fmp4.go
@@ -159,18 +159,22 @@ func (m *muxerSegmenterFMP4) close() {
 	}
 }
 
-func (m *muxerSegmenterFMP4) genSegmentID() uint64 {
+func (m *muxerSegmenterFMP4) takeSegmentID() uint64 {
 	id := m.nextSegmentID
 	m.nextSegmentID++
 	return id
 }
 
-func (m *muxerSegmenterFMP4) genPartID() uint64 {
+func (m *muxerSegmenterFMP4) takePartID() uint64 {
 	id := m.nextPartID
 	m.nextPartID++
 	return id
 }
 
+func (m *muxerSegmenterFMP4) givePartID() {
+	m.nextPartID--
+}
+
 // iPhone iOS fails if part durations are less than 85% of maximum part duration.
 // find a part duration that is compatible with all received sample durations
 func (m *muxerSegmenterFMP4) adjustPartDuration(sampleDuration time.Duration) {
@@ -322,7 +326,7 @@ func (m *muxerSegmenterFMP4) writeVideo(
 		var err error
 		m.currentSegment, err = newMuxerSegmentFMP4(
 			m.lowLatency,
-			m.genSegmentID(),
+			m.takeSegmentID(),
 			sample.ntp,
 			sample.dts,
 			m.segmentMaxSize,
@@ -332,7 +336,8 @@ func (m *muxerSegmenterFMP4) writeVideo(
 			m.prefix,
 			false,
 			m.factory,
-			m.genPartID,
+			m.takePartID,
+			m.givePartID,
 			m.publishPart,
 		)
 		if err != nil {
@@ -365,7 +370,7 @@ func (m *muxerSegmenterFMP4) writeVideo(
 
 		m.currentSegment, err = newMuxerSegmentFMP4(
 			m.lowLatency,
-			m.genSegmentID(),
+			m.takeSegmentID(),
 			m.nextVideoSample.ntp,
 			m.nextVideoSample.dts,
 			m.segmentMaxSize,
@@ -375,7 +380,8 @@ func (m *muxerSegmenterFMP4) writeVideo(
 			m.prefix,
 			forceSwitch,
 			m.factory,
-			m.genPartID,
+			m.takePartID,
+			m.givePartID,
 			m.publishPart,
 		)
 		if err != nil {
@@ -455,7 +461,7 @@ func (m *muxerSegmenterFMP4) writeAudio(ntp time.Time, dts time.Duration, au []b
 			var err error
 			m.currentSegment, err = newMuxerSegmentFMP4(
 				m.lowLatency,
-				m.genSegmentID(),
+				m.takeSegmentID(),
 				sample.ntp,
 				sample.dts,
 				m.segmentMaxSize,
@@ -465,7 +471,8 @@ func (m *muxerSegmenterFMP4) writeAudio(ntp time.Time, dts time.Duration, au []b
 				m.prefix,
 				false,
 				m.factory,
-				m.genPartID,
+				m.takePartID,
+				m.givePartID,
 				m.publishPart,
 			)
 			if err != nil {
@@ -501,7 +508,7 @@ func (m *muxerSegmenterFMP4) writeAudio(ntp time.Time, dts time.Duration, au []b
 
 		m.currentSegment, err = newMuxerSegmentFMP4(
 			m.lowLatency,
-			m.genSegmentID(),
+			m.takeSegmentID(),
 			m.nextAudioSample.ntp,
 			m.nextAudioSample.dts,
 			m.segmentMaxSize,
@@ -511,7 +518,8 @@ func (m *muxerSegmenterFMP4) writeAudio(ntp time.Time, dts time.Duration, au []b
 			m.prefix,
 			false,
 			m.factory,
-			m.genPartID,
+			m.takePartID,
+			m.givePartID,
 			m.publishPart,
 		)
 		if err != nil {

diff --git a/muxer_segmenter_mpegts.go b/muxer_segmenter_mpegts.go
@@ -91,7 +91,7 @@ func (m *muxerSegmenterMPEGTS) close() {
 	}
 }
 
-func (m *muxerSegmenterMPEGTS) genSegmentID() uint64 {
+func (m *muxerSegmenterMPEGTS) takeSegmentID() uint64 {
 	id := m.nextSegmentID
 	m.nextSegmentID++
 	return id
@@ -142,7 +142,7 @@ func (m *muxerSegmenterMPEGTS) writeH26x(
 
 		// create first segment
 		m.currentSegment, err = newMuxerSegmentMPEGTS(
-			m.genSegmentID(),
+			m.takeSegmentID(),
 			ntp,
 			m.segmentMaxSize,
 			m.writerVideoTrack,
@@ -176,7 +176,7 @@ func (m *muxerSegmenterMPEGTS) writeH26x(
 			}
 
 			m.currentSegment, err = newMuxerSegmentMPEGTS(
-				m.genSegmentID(),
+				m.takeSegmentID(),
 				ntp,
 				m.segmentMaxSize,
 				m.writerVideoTrack,
@@ -214,7 +214,7 @@ func (m *muxerSegmenterMPEGTS) writeMPEG4Audio(ntp time.Time, pts time.Duration,
 			// create first segment
 			var err error
 			m.currentSegment, err = newMuxerSegmentMPEGTS(
-				m.genSegmentID(),
+				m.takeSegmentID(),
 				ntp,
 				m.segmentMaxSize,
 				m.writerVideoTrack,
@@ -240,7 +240,7 @@ func (m *muxerSegmenterMPEGTS) writeMPEG4Audio(ntp time.Time, pts time.Duration,
 			}
 
 			m.currentSegment, err = newMuxerSegmentMPEGTS(
-				m.genSegmentID(),
+				m.takeSegmentID(),
 				ntp,
 				m.segmentMaxSize,
 				m.writerVideoTrack,

diff --git a/muxer_test.go b/muxer_test.go
@@ -291,10 +291,10 @@ func TestMuxerVideoAudio(t *testing.T) {
 						`#EXTINF:4.00000,\n` +
 						`(.*?_seg7\.mp4)\n` +
 						`#EXT-X-PROGRAM-DATE-TIME:2010-01-01T01:01:06Z\n` +
-						`#EXT-X-PART:DURATION=1.00000,URI="(.*?_part3\.mp4)",INDEPENDENT=YES\n` +
+						`#EXT-X-PART:DURATION=1.00000,URI="(.*?_part2\.mp4)",INDEPENDENT=YES\n` +
 						`#EXTINF:1.00000,\n` +
 						`(.*?_seg8\.mp4)\n` +
-						`#EXT-X-PRELOAD-HINT:TYPE=PART,URI="(.*?_part4\.mp4)"\n$`)
+						`#EXT-X-PRELOAD-HINT:TYPE=PART,URI="(.*?_part3\.mp4)"\n$`)
 				require.Regexp(t, re, string(byts))
 				ma := re.FindStringSubmatch(string(byts))