OggWriter: add packet segmentation

Author: streamer45

pkg/media/oggwriter/oggwriter.go

@@ -149,22 +149,33 @@ const (
 
 func (i *OggWriter) createPage(payload []uint8, headerType uint8, granulePos uint64, pageIndex uint32) []byte {
 	i.lastPayloadSize = len(payload)
-	page := make([]byte, pageHeaderSize+1+i.lastPayloadSize)
+	nSegments := (len(payload) / 255) + 1 // A segment can be at most 255 bytes long.
+
+	page := make([]byte, pageHeaderSize+i.lastPayloadSize+nSegments)
 
 	copy(page[0:], pageHeaderSignature)                 // page headers starts with 'OggS'
 	page[4] = 0                                         // Version
 	page[5] = headerType                                // 1 = continuation, 2 = beginning of stream, 4 = end of stream
 	binary.LittleEndian.PutUint64(page[6:], granulePos) // granule position
 	binary.LittleEndian.PutUint32(page[14:], i.serial)  // Bitstream serial number
 	binary.LittleEndian.PutUint32(page[18:], pageIndex) // Page sequence number
-	page[26] = 1                                        // Number of segments in page, giving always 1 segment
-	page[27] = uint8(i.lastPayloadSize)                 // Segment Table inserting at 27th position since page header length is 27
-	copy(page[28:], payload)                            // inserting at 28th since Segment Table(1) + header length(27)
+	page[26] = uint8(nSegments)                         // Number of segments in page.
+
+	// Filling segment table with the lacing values.
+	// First (nSegments - 1) values will always be 255.
+	for i := 0; i < nSegments-1; i++ {
+		page[pageHeaderSize+i] = 255
+	}
+	// The last value will be the remainder.
+	page[pageHeaderSize+nSegments-1] = uint8(len(payload) % 255)
+
+	copy(page[pageHeaderSize+nSegments:], payload) // Payload goes after the segment table, so at pageHeaderSize+nSegments.
 
 	var checksum uint32
 	for index := range page {
 		checksum = (checksum << 8) ^ i.checksumTable[byte(checksum>>24)^page[index]]
 	}
+
 	binary.LittleEndian.PutUint32(page[22:], checksum) // Checksum - generating for page data and inserting at 22th position into 32 bits
 
 	return page

pkg/media/oggwriter/oggwriter_test.go

@@ -133,3 +133,33 @@ func TestOggWriter_EmptyPayload(t *testing.T) {
 
 	assert.NoError(t, writer.WriteRTP(&rtp.Packet{Payload: []byte{}}))
 }
+
+func TestOggWriter_LargePayload(t *testing.T) {
+	rawPkt := bytes.Repeat([]byte{0x45}, 1000)
+
+	validPacket := &rtp.Packet{
+		Header: rtp.Header{
+			Marker:           true,
+			Extension:        true,
+			ExtensionProfile: 1,
+			Version:          2,
+			PayloadType:      111,
+			SequenceNumber:   27023,
+			Timestamp:        3653407706,
+			SSRC:             476325762,
+			CSRC:             []uint32{},
+		},
+		Payload: rawPkt,
+	}
+	assert.NoError(t, validPacket.SetExtension(0, []byte{0xFF, 0xFF, 0xFF, 0xFF}))
+
+	writer, err := NewWith(&bytes.Buffer{}, 48000, 2)
+	assert.NoError(t, err, "OggWriter should be created")
+	assert.NotNil(t, writer, "Writer shouldn't be nil")
+
+	err = writer.WriteRTP(validPacket)
+	assert.NoError(t, err)
+
+	data := writer.createPage(rawPkt, pageHeaderTypeContinuationOfStream, 0, 1)
+	assert.Equal(t, uint8(4), data[26])
+}