hls: fix blocking playlists

when hlsVariant is lowLatency and hlsSegmentCount is not 7, segment IDs
where assigned erroneously.

internal/hls/muxer_test.go

@@ -173,10 +173,10 @@ func TestMuxerVideoAudio(t *testing.T) {
 					`\n` +
 					`#EXT-X-PROGRAM-DATE-TIME:(.*?)\n` +
 					`#EXTINF:4.00000,\n` +
-					`(.+?\.mp4)\n` +
+					`(seg0\.mp4)\n` +
 					`#EXT-X-PROGRAM-DATE-TIME:(.*?)\n` +
 					`#EXTINF:1.00000,\n` +
-					`(.+?\.mp4)\n$`)
+					`(seg1\.mp4)\n$`)
 				ma = re.FindStringSubmatch(string(byts))
 			}
 			require.NotEqual(t, 0, len(ma))
@@ -507,10 +507,10 @@ func TestMuxerVideoOnly(t *testing.T) {
 					`\n` +
 					`#EXT-X-PROGRAM-DATE-TIME:(.*?)\n` +
 					`#EXTINF:4.00000,\n` +
-					`(.+?\.mp4)\n` +
+					`(seg0\.mp4)\n` +
 					`#EXT-X-PROGRAM-DATE-TIME:(.*?)\n` +
 					`#EXTINF:1.00000,\n` +
-					`(.+?\.mp4)\n$`)
+					`(seg1\.mp4)\n$`)
 				ma = re.FindStringSubmatch(string(byts))
 			}
 			require.NotEqual(t, 0, len(ma))
@@ -731,10 +731,10 @@ func TestMuxerAudioOnly(t *testing.T) {
 					`\n` +
 					`#EXT-X-PROGRAM-DATE-TIME:(.*?)\n` +
 					`#EXTINF:2.32200,\n` +
-					`(.+?\.mp4)\n` +
+					`(seg0\.mp4)\n` +
 					`#EXT-X-PROGRAM-DATE-TIME:(.*?)\n` +
 					`#EXTINF:0.02322,\n` +
-					`(.+?\.mp4)\n$`)
+					`(seg1\.mp4)\n$`)
 				ma = re.FindStringSubmatch(string(byts))
 			}
 			require.NotEqual(t, 0, len(ma))

internal/hls/muxer_variant_fmp4_playlist.go

@@ -333,7 +333,7 @@ func (p *muxerVariantFMP4Playlist) fullPlaylist(isDeltaUpdate bool) io.Reader {
 			}
 
 			cnt += "#EXTINF:" + strconv.FormatFloat(seg.renderedDuration.Seconds(), 'f', 5, 64) + ",\n" +
-				seg.name() + ".mp4\n"
+				seg.name + ".mp4\n"
 
 		case *muxerVariantFMP4Gap:
 			cnt += "#EXT-X-GAP\n" +
@@ -449,7 +449,7 @@ func (p *muxerVariantFMP4Playlist) onSegmentFinalized(segment *muxerVariantFMP4S
 			}
 		}
 
-		p.segmentsByName[segment.name()] = segment
+		p.segmentsByName[segment.name] = segment
 		p.segments = append(p.segments, segment)
 		p.nextSegmentID = segment.id + 1
 		p.nextSegmentParts = p.nextSegmentParts[:0]
@@ -463,7 +463,7 @@ func (p *muxerVariantFMP4Playlist) onSegmentFinalized(segment *muxerVariantFMP4S
 				}
 				p.parts = p.parts[len(toDeleteSeg.parts):]
 
-				delete(p.segmentsByName, toDeleteSeg.name())
+				delete(p.segmentsByName, toDeleteSeg.name)
 			}
 
 			p.segments = p.segments[1:]

internal/hls/muxer_variant_fmp4_segment.go

@@ -52,6 +52,7 @@ type muxerVariantFMP4Segment struct {
 	genPartID       func() uint64
 	onPartFinalized func(*muxerVariantFMP4Part)
 
+	name             string
 	size             uint64
 	parts            []*muxerVariantFMP4Part
 	currentPart      *muxerVariantFMP4Part
@@ -79,6 +80,7 @@ func newMuxerVariantFMP4Segment(
 		audioTrack:      audioTrack,
 		genPartID:       genPartID,
 		onPartFinalized: onPartFinalized,
+		name:            "seg" + strconv.FormatUint(id, 10),
 	}
 
 	s.currentPart = newMuxerVariantFMP4Part(
@@ -90,10 +92,6 @@ func newMuxerVariantFMP4Segment(
 	return s
 }
 
-func (s *muxerVariantFMP4Segment) name() string {
-	return "seg" + strconv.FormatUint(s.id, 10)
-}
-
 func (s *muxerVariantFMP4Segment) reader() io.Reader {
 	return &partsReader{parts: s.parts}
 }

internal/hls/muxer_variant_fmp4_segmenter.go

@@ -80,7 +80,7 @@ func newMuxerVariantFMP4Segmenter(
 	onSegmentFinalized func(*muxerVariantFMP4Segment),
 	onPartFinalized func(*muxerVariantFMP4Part),
 ) *muxerVariantFMP4Segmenter {
-	return &muxerVariantFMP4Segmenter{
+	m := &muxerVariantFMP4Segmenter{
 		lowLatency:         lowLatency,
 		segmentDuration:    segmentDuration,
 		partDuration:       partDuration,
@@ -89,9 +89,15 @@ func newMuxerVariantFMP4Segmenter(
 		audioTrack:         audioTrack,
 		onSegmentFinalized: onSegmentFinalized,
 		onPartFinalized:    onPartFinalized,
-		nextSegmentID:      uint64(segmentCount),
 		sampleDurations:    make(map[time.Duration]struct{}),
 	}
+
+	// add initial gaps, required by iOS LL-HLS
+	if m.lowLatency {
+		m.nextSegmentID = 7
+	}
+
+	return m
 }
 
 func (m *muxerVariantFMP4Segmenter) genSegmentID() uint64 {