Files
gortsplib/pkg/codecs/mpeg4audio/adts.go

148 lines
3.3 KiB
Go

package mpeg4audio
import (
"fmt"
)
// ADTSPacket is an ADTS packet.
type ADTSPacket struct {
Type ObjectType
SampleRate int
ChannelCount int
AU []byte
}
// ADTSPackets is a group od ADTS packets.
type ADTSPackets []*ADTSPacket
// Unmarshal decodes an ADTS stream into ADTS packets.
func (ps *ADTSPackets) Unmarshal(buf []byte) error {
// refs: https://wiki.multimedia.cx/index.php/ADTS
bl := len(buf)
pos := 0
for {
if (bl - pos) < 8 {
return fmt.Errorf("invalid length")
}
syncWord := (uint16(buf[pos]) << 4) | (uint16(buf[pos+1]) >> 4)
if syncWord != 0xfff {
return fmt.Errorf("invalid syncword")
}
protectionAbsent := buf[pos+1] & 0x01
if protectionAbsent != 1 {
return fmt.Errorf("CRC is not supported")
}
pkt := &ADTSPacket{}
pkt.Type = ObjectType((buf[pos+2] >> 6) + 1)
switch pkt.Type {
case ObjectTypeAACLC:
default:
return fmt.Errorf("unsupported audio type: %d", pkt.Type)
}
sampleRateIndex := (buf[pos+2] >> 2) & 0x0F
switch {
case sampleRateIndex <= 12:
pkt.SampleRate = sampleRates[sampleRateIndex]
default:
return fmt.Errorf("invalid sample rate index: %d", sampleRateIndex)
}
channelConfig := ((buf[pos+2] & 0x01) << 2) | ((buf[pos+3] >> 6) & 0x03)
switch {
case channelConfig >= 1 && channelConfig <= 6:
pkt.ChannelCount = int(channelConfig)
case channelConfig == 7:
pkt.ChannelCount = 8
default:
return fmt.Errorf("invalid channel configuration: %d", channelConfig)
}
frameLen := int(((uint16(buf[pos+3])&0x03)<<11)|
(uint16(buf[pos+4])<<3)|
((uint16(buf[pos+5])>>5)&0x07)) - 7
if frameLen > MaxAccessUnitSize {
return fmt.Errorf("AU size (%d) is too big (maximum is %d)", frameLen, MaxAccessUnitSize)
}
frameCount := buf[pos+6] & 0x03
if frameCount != 0 {
return fmt.Errorf("frame count greater than 1 is not supported")
}
if len(buf[pos+7:]) < frameLen {
return fmt.Errorf("invalid frame length")
}
pkt.AU = buf[pos+7 : pos+7+frameLen]
pos += 7 + frameLen
*ps = append(*ps, pkt)
if (bl - pos) == 0 {
break
}
}
return nil
}
func (ps ADTSPackets) marshalSize() int {
n := 0
for _, pkt := range ps {
n += 7 + len(pkt.AU)
}
return n
}
// Marshal encodes ADTS packets into an ADTS stream.
func (ps ADTSPackets) Marshal() ([]byte, error) {
buf := make([]byte, ps.marshalSize())
pos := 0
for _, pkt := range ps {
sampleRateIndex, ok := reverseSampleRates[pkt.SampleRate]
if !ok {
return nil, fmt.Errorf("invalid sample rate: %d", pkt.SampleRate)
}
var channelConfig int
switch {
case pkt.ChannelCount >= 1 && pkt.ChannelCount <= 6:
channelConfig = pkt.ChannelCount
case pkt.ChannelCount == 8:
channelConfig = 7
default:
return nil, fmt.Errorf("invalid channel count (%d)", pkt.ChannelCount)
}
frameLen := len(pkt.AU) + 7
fullness := 0x07FF // like ffmpeg does
buf[pos+0] = 0xFF
buf[pos+1] = 0xF1
buf[pos+2] = uint8((int(pkt.Type-1) << 6) | (sampleRateIndex << 2) | ((channelConfig >> 2) & 0x01))
buf[pos+3] = uint8((channelConfig&0x03)<<6 | (frameLen>>11)&0x03)
buf[pos+4] = uint8((frameLen >> 3) & 0xFF)
buf[pos+5] = uint8((frameLen&0x07)<<5 | ((fullness >> 6) & 0x1F))
buf[pos+6] = uint8((fullness & 0x3F) << 2)
pos += 7
pos += copy(buf[pos:], pkt.AU)
}
return buf, nil
}