feat: InitSegment.TweakSingleTrakLive to tweak init segments to

CHANGELOG.md

@@ -7,7 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Nothing yet
+### Added
+
+- InitSegment.TweakSingleTrakLive changes an init segment to fit live streaming
 
 ## [0.42.0] - 2024-01-26
 

mp4/initsegment.go

@@ -248,6 +248,29 @@ func (s *InitSegment) GetMediaType() string {
 	}
 }
 
+// TweakSingleTrakLive assures that there is only one track and removes any mehd box.
+func (s *InitSegment) TweakSingleTrakLive() error {
+	if len(s.Moov.Traks) != 1 {
+		return fmt.Errorf("only one track allowed for live")
+	}
+	mvex := s.Moov.Mvex
+	if mvex == nil {
+		return fmt.Errorf("no mvex box found")
+
+	}
+	mehd := mvex.Mehd
+	if mehd != nil {
+		for i, c := range mvex.Children {
+			if c == mehd {
+				mvex.Children = append(mvex.Children[:i], mvex.Children[i+1:]...)
+				mvex.Mehd = nil
+				break
+			}
+		}
+	}
+	return nil
+}
+
 // SetAACDescriptor - Modify a TrakBox by adding AAC SampleDescriptor
 // objType is one of AAClc, HEAACv1, HEAACv2
 // For HEAAC, the samplingFrequency is the base frequency (normally 24000)

mp4/initsegment_test.go

@@ -211,3 +211,37 @@ func TestGenerateInitSegment(t *testing.T) {
 		t.Errorf("Generated init segment different from %s", goldenAssetPath)
 	}
 }
+
+func TestInitTweakSingleTrakLive(t *testing.T) {
+	// Check that mehd box is removed and that multiple tracks is not allowed.
+	goldenAssetPath := "testdata/golden_init_video.mp4"
+	r, err := os.Open(goldenAssetPath)
+	if err != nil {
+		t.Error(err)
+	}
+	f, err := DecodeFile(r)
+	if err != nil {
+		t.Error(err)
+	}
+	moov := f.Init.Moov
+	mvex := moov.Mvex
+	mehd := MehdBox{
+		FragmentDuration: 1000,
+	}
+	mvex.AddChild(&mehd)
+	err = f.Init.TweakSingleTrakLive()
+	if err != nil {
+		t.Error(err)
+	}
+	if mvex.Mehd != nil {
+		t.Errorf("Mehd not removed")
+	}
+	f.Init.AddEmptyTrack(180000, "video", "und")
+	err = f.Init.TweakSingleTrakLive()
+	wantedErrMsg := "only one track allowed for live"
+	if err == nil {
+		t.Errorf("Did not get error")
+	} else if err.Error() != wantedErrMsg {
+		t.Errorf(`Did not get error %q but %q"`, wantedErrMsg, err)
+	}
+}