hls: use fields for each flag values

internal/hls/fmp4/part.go

@@ -13,6 +13,8 @@ const (
 	trunFlagSampleSizePresent                      = 0x200
 	trunFlagSampleFlagsPresent                     = 0x400
 	trunFlagSampleCompositionTimeOffsetPresentOrV1 = 0x800
+
+	sampleFlagIsNonSyncSample = 1 << 16
 )
 
 // Part is a FMP4 part file.
@@ -111,8 +113,8 @@ func (ps *Parts) Unmarshal(byts []byte) error {
 			}
 			trun := box.(*gomp4.Trun)
 
-			flags := uint16(trun.Flags[1])<<8 | uint16(trun.Flags[2])
-			if (flags & trunFlagDataOffsetPreset) == 0 {
+			trunFlags := uint16(trun.Flags[1])<<8 | uint16(trun.Flags[2])
+			if (trunFlags & trunFlagDataOffsetPreset) == 0 {
 				return nil, fmt.Errorf("unsupported flags")
 			}
 
@@ -126,7 +128,7 @@ func (ps *Parts) Unmarshal(byts []byte) error {
 			for i, e := range trun.Entries {
 				s := &PartSample{}
 
-				if (flags & trunFlagSampleDurationPresent) != 0 {
+				if (trunFlags & trunFlagSampleDurationPresent) != 0 {
 					s.Duration = e.SampleDuration
 				} else {
 					s.Duration = tfhd.DefaultSampleDuration
@@ -134,14 +136,16 @@ func (ps *Parts) Unmarshal(byts []byte) error {
 
 				s.PTSOffset = e.SampleCompositionTimeOffsetV1
 
-				if (flags & trunFlagSampleFlagsPresent) != 0 {
-					s.Flags = e.SampleFlags
+				var sampleFlags uint32
+				if (trunFlags & trunFlagSampleFlagsPresent) != 0 {
+					sampleFlags = e.SampleFlags
 				} else {
-					s.Flags = tfhd.DefaultSampleFlags
+					sampleFlags = tfhd.DefaultSampleFlags
 				}
+				s.IsNonSyncSample = ((sampleFlags & sampleFlagIsNonSyncSample) != 0)
 
 				var size uint32
-				if (flags & trunFlagSampleSizePresent) != 0 {
+				if (trunFlags & trunFlagSampleSizePresent) != 0 {
 					size = e.SampleSize
 				} else {
 					size = tfhd.DefaultSampleSize

internal/hls/fmp4/part_test.go

@@ -37,7 +37,7 @@ func TestPartMarshal(t *testing.T) {
 				0x00, 0x00, 0x00, 0x01,
 				0x01, // non-IDR
 			},
-			Flags: 1 << 16,
+			IsNonSyncSample: true,
 		},
 		{
 			Duration: 1 * 90000,
@@ -45,7 +45,7 @@ func TestPartMarshal(t *testing.T) {
 				0x00, 0x00, 0x00, 0x01,
 				0x01, // non-IDR
 			},
-			Flags: 1 << 16,
+			IsNonSyncSample: true,
 		},
 	}
 
@@ -214,7 +214,7 @@ func TestPartUnmarshal(t *testing.T) {
 							0x00, 0x00, 0x00, 0x01,
 							0x01, // non-IDR
 						},
-						Flags: 1 << 16,
+						IsNonSyncSample: true,
 					},
 					{
 						Duration: 1 * 90000,
@@ -222,7 +222,7 @@ func TestPartUnmarshal(t *testing.T) {
 							0x00, 0x00, 0x00, 0x01,
 							0x01, // non-IDR
 						},
-						Flags: 1 << 16,
+						IsNonSyncSample: true,
 					},
 				},
 			},

internal/hls/fmp4/part_track.go

@@ -6,10 +6,10 @@ import (
 
 // PartSample is a sample of a PartTrack.
 type PartSample struct {
-	Duration  uint32
-	PTSOffset int32
-	Flags     uint32
-	Payload   []byte
+	Duration        uint32
+	PTSOffset       int32
+	IsNonSyncSample bool
+	Payload         []byte
 }
 
 // PartTrack is a track of Part.
@@ -78,10 +78,15 @@ func (pt *PartTrack) marshal(w *mp4Writer) (*gomp4.Trun, int, error) {
 
 	for _, sample := range pt.Samples {
 		if pt.IsVideo {
+			var flags uint32
+			if sample.IsNonSyncSample {
+				flags |= sampleFlagIsNonSyncSample
+			}
+
 			trun.Entries = append(trun.Entries, gomp4.TrunEntry{
 				SampleDuration:                sample.Duration,
 				SampleSize:                    uint32(len(sample.Payload)),
-				SampleFlags:                   sample.Flags,
+				SampleFlags:                   flags,
 				SampleCompositionTimeOffsetV1: sample.PTSOffset,
 			})
 		} else {

internal/hls/muxer_variant_fmp4_part.go

@@ -123,7 +123,7 @@ func (p *muxerVariantFMP4Part) writeH264(sample *augmentedVideoSample) {
 		p.videoStartDTS = sample.dts
 	}
 
-	if (sample.Flags & (1 << 16)) == 0 {
+	if !sample.IsNonSyncSample {
 		p.isIndependent = true
 	}
 

internal/hls/muxer_variant_fmp4_segmenter.go

@@ -203,16 +203,11 @@ func (m *muxerVariantFMP4Segmenter) writeH264Entry(
 		return err
 	}
 
-	var flags uint32
-	if !idrPresent {
-		flags |= 1 << 16
-	}
-
 	sample := &augmentedVideoSample{
 		PartSample: fmp4.PartSample{
-			PTSOffset: int32(durationGoToMp4(pts-dts, 90000)),
-			Flags:     flags,
-			Payload:   avcc,
+			PTSOffset:       int32(durationGoToMp4(pts-dts, 90000)),
+			IsNonSyncSample: !idrPresent,
+			Payload:         avcc,
 		},
 		dts: dts,
 	}