feat: support #EXT-X-PART-INF:PART-TARGET tag

Eyevinn · Feb 10, 2025 · a5b9892 · a5b9892
1 parent 6f2d765
commit a5b9892
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Showing 7 changed files with 75 additions and 1 deletion.
diff --git a/m3u8/read_write_test.go b/m3u8/read_write_test.go
@@ -398,6 +398,7 @@ func TestReadWritePlaylists(t *testing.T) {
 		"media-playlist-with-multiple-dateranges.m3u8",
 		"media-playlist-with-start-time.m3u8",
 		"master-with-independent-segments.m3u8",
+		// "media-playlist-low-latency.m3u8",
 	}
 
 	for _, fileName := range files {

diff --git a/m3u8/reader.go b/m3u8/reader.go
@@ -874,6 +874,11 @@ func decodeLineOfMediaPlaylist(p *MediaPlaylist, state *decodingState, line stri
 		if _, err = fmt.Sscanf(line, "#EXT-X-TARGETDURATION:%d", &p.TargetDuration); strict && err != nil {
 			return err
 		}
+	case strings.HasPrefix(line, "#EXT-X-PART-INF:PART-TARGET="):
+		state.listType = MEDIA
+		if _, err = fmt.Sscanf(line, "#EXT-X-PART-INF:PART-TARGET=%f", &p.PartTargetDuration); strict && err != nil {
+			return err
+		}
 	case strings.HasPrefix(line, "#EXT-X-MEDIA-SEQUENCE:"):
 		state.listType = MEDIA
 		if _, err = fmt.Sscanf(line, "#EXT-X-MEDIA-SEQUENCE:%d", &p.SeqNo); strict && err != nil {

diff --git a/m3u8/reader_test.go b/m3u8/reader_test.go
@@ -862,6 +862,22 @@ func TestMediaPlaylistWithSCTE35Tag(t *testing.T) {
 	}
 }
 
+func TestDecodeLowLatencyMediaPlaylist(t *testing.T) {
+	is := is.New(t)
+	f, err := os.Open("sample-playlists/media-playlist-low-latency.m3u8")
+	is.NoErr(err) // must open file
+	p, listType, err := DecodeFrom(bufio.NewReader(f), true)
+	is.NoErr(err) // must decode playlist
+	pp := p.(*MediaPlaylist)
+	CheckType(t, pp)
+	is.Equal(listType, MEDIA) // must be media playlist
+	// check parsed values
+	is.Equal(pp.TargetDuration, uint(4))               // target duration must be 15
+	is.True(!pp.Closed)                                // live playlist
+	is.Equal(pp.SeqNo, uint64(0))                      // sequence number must be 0
+	is.Equal(pp.PartTargetDuration, float32(1.002000)) // part target duration must be 1.002000
+}
+
 func TestDecodeMediaPlaylistWithProgramDateTime(t *testing.T) {
 	is := is.New(t)
 	f, err := os.Open("sample-playlists/media-playlist-with-program-date-time.m3u8")

diff --git a/m3u8/sample-playlists/media-playlist-low-latency.m3u8 b/m3u8/sample-playlists/media-playlist-low-latency.m3u8
@@ -0,0 +1,28 @@
+#EXTM3U
+#EXT-X-TARGETDURATION:4
+#EXT-X-VERSION:6
+#EXT-X-PART-INF:PART-TARGET=1.002000
+#EXT-X-MEDIA-SEQUENCE:0
+#EXT-X-PROGRAM-DATE-TIME:2025-02-10T13:17:05.056Z
+#EXT-X-MAP:URI="fileSequence0.mp4"
+#EXTINF:4.00000,
+fileSequence1.m4s
+#EXTINF:4.00000,
+fileSequence2.m4s
+#EXTINF:4.00000,
+fileSequence3.m4s
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart4.1.m4s"
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart4.2.m4s"
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart4.3.m4s"
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart4.4.m4s"
+#EXTINF:4.00000,
+fileSequence4.m4s
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart5.1.m4s"
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart5.2.m4s"
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart5.3.m4s"
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart5.4.m4s"
+#EXTINF:4.00000,
+fileSequence5.m4s
+#EXT-X-PROGRAM-DATE-TIME:2025-02-10T13:17:25.056Z
+#EXT-X-PART:DURATION=1.00000,INDEPENDENT=YES,URI="filePart6.1.m4s"
+#EXT-X-PRELOAD-HINT:TYPE=PART,URI="filePart6.2.m4s"
diff --git a/m3u8/structure.go b/m3u8/structure.go
@@ -141,7 +141,7 @@ type MediaPlaylist struct {
 	ver                 uint8           // protocol version of the playlist, 3 or higher
 	targetDurLocked     bool            // target duration is locked and cannot be changed
 	independentSegments bool            // Global tag for EXT-X-INDEPENDENT-SEGMENTS
-
+	PartTargetDuration  float32         // EXT-X-PART-INF:PART-TARGET
 }
 
 // MasterPlaylist represents a master (multivariant) playlist which

diff --git a/m3u8/writer.go b/m3u8/writer.go
@@ -689,6 +689,11 @@ func (p *MediaPlaylist) Encode() *bytes.Buffer {
 			p.buf.WriteString("VOD\n")
 		}
 	}
+	if p.PartTargetDuration > 0 {
+		p.buf.WriteString("#EXT-X-PART-INF:PART-TARGET=")
+		p.buf.WriteString(strconv.FormatFloat(float64(p.PartTargetDuration), 'f', 6, 64))
+		p.buf.WriteRune('\n')
+	}
 	p.buf.WriteString("#EXT-X-MEDIA-SEQUENCE:")
 	p.buf.WriteString(strconv.FormatUint(p.SeqNo, 10))
 	p.buf.WriteRune('\n')

diff --git a/m3u8/writer_test.go b/m3u8/writer_test.go
@@ -369,6 +369,25 @@ test01.ts
 	is.Equal(out, expected) // Encode media playlist does not match expected
 }
 
+func TestEncodeLowLatencyMediaPlaylist(t *testing.T) {
+	is := is.New(t)
+	p, e := NewMediaPlaylist(3, 5)
+	is.NoErr(e) // Create media playlist should be successful
+	p.PartTargetDuration = 1.002
+	e = p.Append("test01.ts", 5.0, "")
+	is.NoErr(e) // Add 1st segment to a media playlist should be successful
+	expected := `#EXTM3U
+#EXT-X-VERSION:3
+#EXT-X-PART-INF:PART-TARGET=1.002000
+#EXT-X-MEDIA-SEQUENCE:0
+#EXT-X-TARGETDURATION:5
+#EXTINF:5.000,
+test01.ts
+`
+	out := p.String()
+	is.Equal(out, expected) // Encode media playlist does not match expected
+}
+
 // Create new media playlist
 // Add 10 segments to media playlist
 // Test iterating over segments