merge MPEG4AudioGeneric and MPEG4AudioLATM (#430)

pkg/format/rtpmpeg4audio/decoder_generic.go

@@ -0,0 +1,190 @@
+package rtpmpeg4audio
+
+import (
+	"fmt"
+
+	"github.com/bluenviron/mediacommon/pkg/bits"
+	"github.com/bluenviron/mediacommon/pkg/codecs/mpeg4audio"
+	"github.com/pion/rtp"
+)
+
+func (d *Decoder) decodeGeneric(pkt *rtp.Packet) ([][]byte, error) {
+	if len(pkt.Payload) < 2 {
+		d.fragments = d.fragments[:0] // discard pending fragments
+		return nil, fmt.Errorf("payload is too short")
+	}
+
+	// AU-headers-length (16 bits)
+	headersLen := int(uint16(pkt.Payload[0])<<8 | uint16(pkt.Payload[1]))
+	if headersLen == 0 {
+		d.fragments = d.fragments[:0] // discard pending fragments
+		return nil, fmt.Errorf("invalid AU-headers-length")
+	}
+	payload := pkt.Payload[2:]
+
+	// AU-headers
+	dataLens, err := d.readAUHeaders(payload, headersLen)
+	if err != nil {
+		d.fragments = d.fragments[:0] // discard pending fragments
+		return nil, err
+	}
+
+	pos := (headersLen / 8)
+	if (headersLen % 8) != 0 {
+		pos++
+	}
+	payload = payload[pos:]
+
+	var aus [][]byte
+
+	if len(d.fragments) == 0 {
+		if pkt.Marker {
+			// AUs
+			aus = make([][]byte, len(dataLens))
+			for i, dataLen := range dataLens {
+				if len(payload) < int(dataLen) {
+					return nil, fmt.Errorf("payload is too short")
+				}
+
+				aus[i] = payload[:dataLen]
+				payload = payload[dataLen:]
+			}
+		} else {
+			if len(dataLens) != 1 {
+				return nil, fmt.Errorf("a fragmented packet can only contain one AU")
+			}
+
+			if len(payload) < int(dataLens[0]) {
+				return nil, fmt.Errorf("payload is too short")
+			}
+
+			d.fragmentsSize = int(dataLens[0])
+			d.fragments = append(d.fragments, payload[:dataLens[0]])
+			return nil, ErrMorePacketsNeeded
+		}
+	} else {
+		// we are decoding a fragmented AU
+		if len(dataLens) != 1 {
+			d.fragments = d.fragments[:0] // discard pending fragments
+			return nil, fmt.Errorf("a fragmented packet can only contain one AU")
+		}
+
+		if len(payload) < int(dataLens[0]) {
+			d.fragments = d.fragments[:0] // discard pending fragments
+			return nil, fmt.Errorf("payload is too short")
+		}
+
+		d.fragmentsSize += int(dataLens[0])
+		if d.fragmentsSize > mpeg4audio.MaxAccessUnitSize {
+			d.fragments = d.fragments[:0] // discard pending fragments
+			return nil, fmt.Errorf("access unit size (%d) is too big, maximum is %d",
+				d.fragmentsSize, mpeg4audio.MaxAccessUnitSize)
+		}
+
+		d.fragments = append(d.fragments, payload[:dataLens[0]])
+
+		if !pkt.Marker {
+			return nil, ErrMorePacketsNeeded
+		}
+
+		aus = [][]byte{joinFragments(d.fragments, d.fragmentsSize)}
+		d.fragments = d.fragments[:0]
+	}
+
+	return d.removeADTS(aus)
+}
+
+func (d *Decoder) readAUHeaders(buf []byte, headersLen int) ([]uint64, error) {
+	firstRead := false
+
+	count := 0
+	for i := 0; i < headersLen; {
+		if i == 0 {
+			i += d.SizeLength
+			i += d.IndexLength
+		} else {
+			i += d.SizeLength
+			i += d.IndexDeltaLength
+		}
+		count++
+	}
+
+	dataLens := make([]uint64, count)
+
+	pos := 0
+	i := 0
+
+	for headersLen > 0 {
+		dataLen, err := bits.ReadBits(buf, &pos, d.SizeLength)
+		if err != nil {
+			return nil, err
+		}
+		headersLen -= d.SizeLength
+
+		if !firstRead {
+			firstRead = true
+			if d.IndexLength > 0 {
+				auIndex, err := bits.ReadBits(buf, &pos, d.IndexLength)
+				if err != nil {
+					return nil, err
+				}
+				headersLen -= d.IndexLength
+
+				if auIndex != 0 {
+					return nil, fmt.Errorf("AU-index different than zero is not supported")
+				}
+			}
+		} else if d.IndexDeltaLength > 0 {
+			auIndexDelta, err := bits.ReadBits(buf, &pos, d.IndexDeltaLength)
+			if err != nil {
+				return nil, err
+			}
+			headersLen -= d.IndexDeltaLength
+
+			if auIndexDelta != 0 {
+				return nil, fmt.Errorf("AU-index-delta different than zero is not supported")
+			}
+		}
+
+		dataLens[i] = dataLen
+		i++
+	}
+
+	return dataLens, nil
+}
+
+// some cameras wrap AUs into ADTS
+func (d *Decoder) removeADTS(aus [][]byte) ([][]byte, error) {
+	if !d.firstAUParsed {
+		d.firstAUParsed = true
+
+		if len(aus) == 1 && len(aus[0]) >= 2 {
+			if aus[0][0] == 0xFF && (aus[0][1]&0xF0) == 0xF0 {
+				var pkts mpeg4audio.ADTSPackets
+				err := pkts.Unmarshal(aus[0])
+				if err == nil && len(pkts) == 1 {
+					d.adtsMode = true
+					aus[0] = pkts[0].AU
+				}
+			}
+		}
+	} else if d.adtsMode {
+		if len(aus) != 1 {
+			return nil, fmt.Errorf("multiple AUs in ADTS mode are not supported")
+		}
+
+		var pkts mpeg4audio.ADTSPackets
+		err := pkts.Unmarshal(aus[0])
+		if err != nil {
+			return nil, fmt.Errorf("unable to decode ADTS: %s", err)
+		}
+
+		if len(pkts) != 1 {
+			return nil, fmt.Errorf("multiple ADTS packets are not supported")
+		}
+
+		aus[0] = pkts[0].AU
+	}
+
+	return aus, nil
+}