From 9b14d00b1e9b69f48bdd0bf156c123084e6ad9ae Mon Sep 17 00:00:00 2001
From: Eric Lindvall <eric@5stops.com>
Date: Sun, 14 Apr 2019 21:19:55 -0700
Subject: [PATCH] Add support for EXT-X-START

---
 reader.go      | 14 ++++++++++++++
 reader_test.go | 19 +++++++++++++++++++
 structure.go   |  4 +++-
 writer.go      |  8 ++++++++
 writer_test.go | 15 +++++++++++++++
 5 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/reader.go b/reader.go
index 14c1f899..0b449fc0 100644
--- a/reader.go
+++ b/reader.go
@@ -490,6 +490,20 @@ func decodeLineOfMediaPlaylist(p *MediaPlaylist, wv *WV, state *decodingState, l
 		if _, err = fmt.Sscanf(line, "#EXT-X-DISCONTINUITY-SEQUENCE:%d", &p.DiscontinuitySeq); strict && err != nil {
 			return err
 		}
+	case strings.HasPrefix(line, "#EXT-X-START:"):
+		state.listType = MEDIA
+		for k, v := range decodeParamsLine(line[13:]) {
+			switch k {
+			case "TIME-OFFSET":
+				st, err := strconv.ParseFloat(v, 64)
+				if err != nil {
+					return fmt.Errorf("Invalid TIME-OFFSET: %s: %v", v, err)
+				}
+				p.StartTime = st
+			case "PRECISE":
+				p.StartTimePrecise = v == "YES"
+			}
+		}
 	case strings.HasPrefix(line, "#EXT-X-KEY:"):
 		state.listType = MEDIA
 		state.xkey = new(Key)
diff --git a/reader_test.go b/reader_test.go
index 4b491635..230badbf 100644
--- a/reader_test.go
+++ b/reader_test.go
@@ -665,6 +665,25 @@ func TestDecodeMediaPlaylistWithProgramDateTime(t *testing.T) {
 	}
 }
 
+func TestDecodeMediaPlaylistStartTime(t *testing.T) {
+	f, err := os.Open("sample-playlists/media-playlist-with-start-time.m3u8")
+	if err != nil {
+		t.Fatal(err)
+	}
+	p, listType, err := DecodeFrom(bufio.NewReader(f), true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	pp := p.(*MediaPlaylist)
+	CheckType(t, pp)
+	if listType != MEDIA {
+		t.Error("Sample not recognized as media playlist.")
+	}
+	if pp.StartTime != float64(8.0) {
+		t.Errorf("Media segment StartTime != 8: %f", pp.StartTime)
+	}
+}
+
 /****************
  *  Benchmarks  *
  ****************/
diff --git a/structure.go b/structure.go
index 06e77408..7bd0ac2f 100644
--- a/structure.go
+++ b/structure.go
@@ -110,7 +110,9 @@ type MediaPlaylist struct {
 	Closed           bool   // is this VOD (closed) or Live (sliding) playlist?
 	MediaType        MediaType
 	DiscontinuitySeq uint64 // EXT-X-DISCONTINUITY-SEQUENCE
-	durationAsInt    bool   // output durations as integers of floats?
+	StartTime        float64
+	StartTimePrecise bool
+	durationAsInt    bool // output durations as integers of floats?
 	keyformat        int
 	winsize          uint // max number of segments displayed in an encoded playlist; need set to zero for VOD playlists
 	capacity         uint // total capacity of slice used for the playlist
diff --git a/writer.go b/writer.go
index c27c0d25..236b071b 100644
--- a/writer.go
+++ b/writer.go
@@ -418,6 +418,14 @@ func (p *MediaPlaylist) Encode() *bytes.Buffer {
 	p.buf.WriteString("#EXT-X-TARGETDURATION:")
 	p.buf.WriteString(strconv.FormatInt(int64(math.Ceil(p.TargetDuration)), 10)) // due section 3.4.2 of M3U8 specs EXT-X-TARGETDURATION must be integer
 	p.buf.WriteRune('\n')
+	if p.StartTime > 0.0 {
+		p.buf.WriteString("#EXT-X-START:TIME-OFFSET=")
+		p.buf.WriteString(strconv.FormatFloat(p.StartTime, 'f', -1, 64))
+		if p.StartTimePrecise {
+			p.buf.WriteString(",PRECISE=YES")
+		}
+		p.buf.WriteRune('\n')
+	}
 	if p.DiscontinuitySeq != 0 {
 		p.buf.WriteString("#EXT-X-DISCONTINUITY-SEQUENCE:")
 		p.buf.WriteString(strconv.FormatUint(uint64(p.DiscontinuitySeq), 10))
diff --git a/writer_test.go b/writer_test.go
index a77c67a1..9784b290 100644
--- a/writer_test.go
+++ b/writer_test.go
@@ -614,6 +614,21 @@ func TestIndependentSegments(t *testing.T) {
 	}
 }
 
+// Create new media playlist
+// Set default map
+func TestStartTimeOffset(t *testing.T) {
+	p, e := NewMediaPlaylist(3, 5)
+	if e != nil {
+		t.Fatalf("Create media playlist failed: %s", e)
+	}
+	p.StartTime = 3.4
+
+	expected := `#EXT-X-START:TIME-OFFSET=3.4`
+	if !strings.Contains(p.String(), expected) {
+		t.Fatalf("Media playlist did not contain: %s\nMedia Playlist:\n%v", expected, p.String())
+	}
+}
+
 func TestMediaPlaylist_Slide(t *testing.T) {
 	m, e := NewMediaPlaylist(3, 4)
 	if e != nil {