Fix WebM SeekHead (#89)

Disable SeekHead calculation by default and remove SeekPosition to Cluster according to Matroska File Format section 5.3. (2009 version) (draft-lhomme-cellar-matroska-04 says that SeekHead must have all top-level elements.) Having only first Cluster SeekPosition looks causing problem on some player.
at-wat · Dec 16, 2019 · de19aaf · de19aaf
1 parent 637c037
commit de19aaf
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Showing 3 changed files with 7 additions and 16 deletions.
diff --git a/webm/blockwriter.go b/webm/blockwriter.go
@@ -79,7 +79,7 @@ func NewSimpleBlockWriter(w0 io.WriteCloser, tracks []TrackEntry, opts ...BlockW
 			panic(err)
 		},
 		interceptor: DefaultBlockInterceptor,
-		seekHead:    true,
+		seekHead:    false,
 	}
 	for _, o := range opts {
 		if err := o(options); err != nil {

diff --git a/webm/blockwriter_test.go b/webm/blockwriter_test.go
@@ -588,27 +588,24 @@ func TestBlockWriter_WithSeekHead(t *testing.T) {
 		// Segment
 		0x18, 0x53, 0x80, 0x67, 0x01, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
 		// SeekHead
-		0x11, 0x4D, 0x9B, 0x74, 0xBF,
+		0x11, 0x4D, 0x9B, 0x74, 0xAA,
 		0x4D, 0xBB, 0x92,
 		0x53, 0xAB, 0x84, 0x15, 0x49, 0xA9, 0x66, // Info
-		0x53, 0xAC, 0x88, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44,
+		0x53, 0xAC, 0x88, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2F,
 		0x4D, 0xBB, 0x92,
 		0x53, 0xAB, 0x84, 0x16, 0x54, 0xAE, 0x6B, // Tracks
-		0x53, 0xAC, 0x88, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x50,
-		0x4D, 0xBB, 0x92,
-		0x53, 0xAB, 0x84, 0x1F, 0x43, 0xB6, 0x75, // Cluster
-		0x53, 0xAC, 0x88, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x64,
-		// Info, pos: 80
+		0x53, 0xAC, 0x88, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3B,
+		// Info, pos: 47
 		0x15, 0x49, 0xA9, 0x66, 0x87,
 		0x2A, 0xD7, 0xB1, 0x83, 0x0F, 0x42, 0x40,
-		// Tracks, pos: 92
+		// Tracks, pos: 59
 		0x16, 0x54, 0xAE, 0x6B, 0x8F,
 		0xAE, 0x8D,
 		0xD7, 0x81, 0x01,
 		0x73, 0xC5, 0x81, 0x02,
 		0x86, 0x81, 0x00,
 		0x83, 0x81, 0x01,
-		// Cluster, pos: 112
+		// Cluster
 		0x1F, 0x43, 0xB6, 0x75, 0x01, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
 		0xE7, 0x81, 0x00,
 	}

diff --git a/webm/seekhead.go b/webm/seekhead.go
@@ -44,7 +44,6 @@ type flexHeader struct {
 func setSeekHead(header *flexHeader, opts ...ebml.MarshalOption) error {
 	infoPos := new(uint64)
 	tracksPos := new(uint64)
-	clusterPos := new(uint64)
 	header.Segment.SeekHead = &seekHeadFixed{}
 	if header.Segment.Info != nil {
 		header.Segment.SeekHead.Seek = append(header.Segment.SeekHead.Seek, seekFixed{
@@ -56,10 +55,6 @@ func setSeekHead(header *flexHeader, opts ...ebml.MarshalOption) error {
 		SeekID:       ebml.ElementTracks.Bytes(),
 		SeekPosition: tracksPos,
 	})
-	header.Segment.SeekHead.Seek = append(header.Segment.SeekHead.Seek, seekFixed{
-		SeekID:       ebml.ElementCluster.Bytes(),
-		SeekPosition: clusterPos,
-	})
 
 	var segmentPos uint64
 	hook := func(e *ebml.Element) {
@@ -82,7 +77,6 @@ func setSeekHead(header *flexHeader, opts ...ebml.MarshalOption) error {
 	if err := ebml.Marshal(header, buf, optsWithHook...); err != nil {
 		return err
 	}
-	*clusterPos = uint64(buf.Len()) - segmentPos
 
 	return nil
 }