streaming

commit 9c432babde8714bfa10488cf39bbabb0e476d3b5
parent 47d1cec1ab17a35dffdab92234fa96b52131e105
Author: Oliver Lowe <o@olowe.co>
Date:   Wed,  8 May 2024 16:43:26 +1000

internal/scte35: implement decoding of splice info descriptors

Only a generic SpliceDescriptor. Decoding of specific descriptors will
come later.

Diffstat:
M
internal/scte35/splice_descriptor.go
 | 
35
+++++++++++++++++++++++++++++------
M
internal/scte35/splice_info.go
 | 
12
++++++++++--

2 files changed, 39 insertions(+), 8 deletions(-)
diff --git a/internal/scte35/splice_descriptor.go b/internal/scte35/splice_descriptor.go
@@ -146,15 +146,38 @@ type AudioChannel struct {
 	FullService bool
 }
 
+func DecodeAllDescriptors(buf []byte) ([]SpliceDescriptor, error) {
+	var sds []SpliceDescriptor
+	for len(buf) > 0 {
+		desc, err := UnmarshalSpliceDescriptor(buf)
+		if err != nil {
+			return sds, err
+		}
+		sds = append(sds, *desc)
+		// desc.Tag + desclength + desc.ID + data
+		dlen := 1 + 1 + 4 + len(desc.Data)
+		if dlen >= len(buf) {
+			break
+		}
+		buf = buf[dlen:]
+		fmt.Println("bytes left in decode loop:", len(buf))
+	}
+	return sds, nil
+}
+
 func UnmarshalSpliceDescriptor(buf []byte) (*SpliceDescriptor, error) {
-	if len(buf) < 5 {
+	if len(buf) < 6 {
 		return nil, fmt.Errorf("need at least 5 bytes")
 	}
-	return &SpliceDescriptor{
-		Tag:  uint8(buf[0]),
-		ID:   binary.LittleEndian.Uint32(buf[1:4]),
-		Data: buf[5:],
-	}, nil
+	d := &SpliceDescriptor{
+		Tag: uint8(buf[0]),
+		ID:  binary.LittleEndian.Uint32(buf[2:6]),
+	}
+	length := uint8(buf[1])
+	if uint8(buf[1]) > 0 {
+		d.Data = buf[6 : 6+length]
+	}
+	return d, nil
 }
 
 func encodeSegDescriptor(sd *SegmentationDescriptor) []byte {
diff --git a/internal/scte35/splice_info.go b/internal/scte35/splice_info.go
@@ -182,7 +182,7 @@ func decodeSpliceInfo(buf []byte) (*SpliceInfo, error) {
 	cmdbuf := buf[11 : 11+cmdlength]
 	switch cmd.Type {
 	case SpliceNull, BandwidthReservation:
-		//
+		// nothing to decode
 	case TimeSignal:
 		// check if time specified flag is set.
 		if cmdbuf[0]&0x80 == 1<<7 {
@@ -196,8 +196,16 @@ func decodeSpliceInfo(buf []byte) (*SpliceInfo, error) {
 			cmd.TimeSignal = &t
 		}
 	default:
-		return nil, fmt.Errorf("cannot decode command %s", cmd.Type)
+		return nil, fmt.Errorf("cannot decode command type %s", cmd.Type)
 	}
 	info.Command = &cmd
+	buf = buf[11+cmdlength:]
+
+	desclen := binary.BigEndian.Uint16([]byte{buf[0], buf[1]})
+	descriptors, err := DecodeAllDescriptors(buf[2 : 2+desclen])
+	if err != nil {
+		return nil, fmt.Errorf("decode splice descriptors: %w", err)
+	}
+	info.Descriptors = descriptors
 	return &info, nil
 }