mirror of
https://github.com/AlexxIT/go2rtc.git
synced 2025-09-26 20:31:11 +08:00
434 lines
9.6 KiB
Go
434 lines
9.6 KiB
Go
package mpegts
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import (
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"bytes"
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"errors"
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"io"
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"github.com/AlexxIT/go2rtc/pkg/aac"
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"github.com/AlexxIT/go2rtc/pkg/bits"
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"github.com/AlexxIT/go2rtc/pkg/h264/annexb"
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"github.com/pion/rtp"
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)
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type Demuxer struct {
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buf [PacketSize]byte // total buf
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byte byte // current byte
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bits byte // bits left in byte
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pos byte // current pos in buf
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end byte // end position
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pmtID uint16 // Program Map Table (PMT) PID
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pes map[uint16]*PES
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}
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func NewDemuxer() *Demuxer {
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return &Demuxer{}
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}
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const skipRead = 0xFF
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func (d *Demuxer) ReadPacket(rd io.Reader) (*rtp.Packet, error) {
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for {
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if d.pos != skipRead {
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if _, err := io.ReadFull(rd, d.buf[:]); err != nil {
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return nil, err
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}
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}
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pid, start, err := d.readPacketHeader()
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if err != nil {
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return nil, err
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}
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if d.pes == nil {
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switch pid {
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case 0: // PAT ID
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d.readPAT() // PAT: Program Association Table
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case d.pmtID:
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d.readPMT() // PMT : Program Map Table
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pkt := &rtp.Packet{
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Payload: make([]byte, 0, len(d.pes)),
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}
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for _, pes := range d.pes {
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pkt.Payload = append(pkt.Payload, pes.StreamType)
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}
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return pkt, nil
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}
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continue
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}
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if pkt := d.readPES(pid, start); pkt != nil {
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return pkt, nil
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}
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}
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}
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func (d *Demuxer) readPacketHeader() (pid uint16, start bool, err error) {
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d.reset()
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sb := d.readByte() // Sync byte
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if sb != SyncByte {
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return 0, false, errors.New("mpegts: wrong sync byte")
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}
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_ = d.readBit() // Transport error indicator (TEI)
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pusi := d.readBit() // Payload unit start indicator (PUSI)
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_ = d.readBit() // Transport priority
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pid = d.readBits16(13) // PID
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_ = d.readBits(2) // Transport scrambling control (TSC)
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af := d.readBit() // Adaptation field
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_ = d.readBit() // Payload
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_ = d.readBits(4) // Continuity counter
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if af != 0 {
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adSize := d.readByte() // Adaptation field length
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if adSize > PacketSize-6 {
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return 0, false, errors.New("mpegts: wrong adaptation size")
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}
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d.skip(adSize)
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}
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return pid, pusi != 0, nil
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}
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func (d *Demuxer) skip(i byte) {
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d.pos += i
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}
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func (d *Demuxer) readBytes(i byte) []byte {
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d.pos += i
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return d.buf[d.pos-i : d.pos]
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}
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func (d *Demuxer) readPSIHeader() {
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// https://en.wikipedia.org/wiki/Program-specific_information#Table_Sections
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pointer := d.readByte() // Pointer field
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d.skip(pointer) // Pointer filler bytes
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_ = d.readByte() // Table ID
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_ = d.readBit() // Section syntax indicator
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_ = d.readBit() // Private bit
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_ = d.readBits(2) // Reserved bits
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_ = d.readBits(2) // Section length unused bits
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size := d.readBits(10) // Section length
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d.setSize(byte(size))
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_ = d.readBits(16) // Table ID extension
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_ = d.readBits(2) // Reserved bits
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_ = d.readBits(5) // Version number
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_ = d.readBit() // Current/next indicator
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_ = d.readByte() // Section number
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_ = d.readByte() // Last section number
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}
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// ReadPAT (Program Association Table)
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func (d *Demuxer) readPAT() {
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// https://en.wikipedia.org/wiki/Program-specific_information#PAT_(Program_Association_Table)
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d.readPSIHeader()
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const CRCSize = 4
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for d.left() > CRCSize {
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num := d.readBits(16) // Program num
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_ = d.readBits(3) // Reserved bits
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pid := d.readBits16(13) // Program map PID
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if num != 0 {
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d.pmtID = pid
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}
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}
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d.skip(4) // CRC32
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}
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// ReadPMT (Program map specific data)
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func (d *Demuxer) readPMT() {
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// https://en.wikipedia.org/wiki/Program-specific_information#PMT_(Program_map_specific_data)
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d.readPSIHeader()
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_ = d.readBits(3) // Reserved bits
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_ = d.readBits(13) // PCR PID
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_ = d.readBits(4) // Reserved bits
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_ = d.readBits(2) // Program info length unused bits
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size := d.readBits(10) // Program info length
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d.skip(byte(size))
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d.pes = map[uint16]*PES{}
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const CRCSize = 4
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for d.left() > CRCSize {
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streamType := d.readByte() // Stream type
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_ = d.readBits(3) // Reserved bits
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pid := d.readBits16(13) // Elementary PID
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_ = d.readBits(4) // Reserved bits
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_ = d.readBits(2) // ES Info length unused bits
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size = d.readBits(10) // ES Info length
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info := d.readBytes(byte(size))
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if streamType == StreamTypePrivate && bytes.HasPrefix(info, opusInfo) {
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streamType = StreamTypePrivateOPUS
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}
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d.pes[pid] = &PES{StreamType: streamType}
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}
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d.skip(4) // CRC32
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}
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func (d *Demuxer) readPES(pid uint16, start bool) *rtp.Packet {
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pes := d.pes[pid]
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if pes == nil {
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return nil
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}
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// if new payload beging
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if start {
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if len(pes.Payload) != 0 {
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d.pos = skipRead
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return pes.GetPacket() // finish previous packet
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}
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// https://en.wikipedia.org/wiki/Packetized_elementary_stream
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// Packet start code prefix
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if d.readByte() != 0 || d.readByte() != 0 || d.readByte() != 1 {
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return nil
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}
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pes.StreamID = d.readByte() // Stream id
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packetSize := d.readBits16(16) // PES Packet length
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_ = d.readBits(2) // Marker bits
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_ = d.readBits(2) // Scrambling control
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_ = d.readBit() // Priority
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_ = d.readBit() // Data alignment indicator
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_ = d.readBit() // Copyright
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_ = d.readBit() // Original or Copy
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ptsi := d.readBit() // PTS indicator
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dtsi := d.readBit() // DTS indicator
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_ = d.readBit() // ESCR flag
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_ = d.readBit() // ES rate flag
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_ = d.readBit() // DSM trick mode flag
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_ = d.readBit() // Additional copy info flag
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_ = d.readBit() // CRC flag
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_ = d.readBit() // extension flag
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headerSize := d.readByte() // PES header length
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if packetSize != 0 {
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packetSize -= uint16(3 + headerSize)
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}
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if ptsi != 0 {
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pes.PTS = d.readTime()
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headerSize -= 5
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} else {
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pes.PTS = 0
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}
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if dtsi != 0 {
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pes.DTS = d.readTime()
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headerSize -= 5
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} else {
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pes.DTS = 0
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}
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d.skip(headerSize)
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pes.SetBuffer(packetSize, d.bytes())
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} else {
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pes.AppendBuffer(d.bytes())
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}
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if pes.Size != 0 && len(pes.Payload) >= pes.Size {
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return pes.GetPacket() // finish current packet
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}
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return nil
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}
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func (d *Demuxer) reset() {
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d.pos = 0
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d.end = PacketSize
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d.bits = 0
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}
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//goland:noinspection GoStandardMethods
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func (d *Demuxer) readByte() byte {
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if d.bits != 0 {
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return byte(d.readBits(8))
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}
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b := d.buf[d.pos]
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d.pos++
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return b
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}
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func (d *Demuxer) readBit() byte {
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if d.bits == 0 {
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d.byte = d.readByte()
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d.bits = 7
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} else {
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d.bits--
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}
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return (d.byte >> d.bits) & 0b1
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}
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func (d *Demuxer) readBits(n byte) (res uint32) {
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for i := n - 1; i != 255; i-- {
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res |= uint32(d.readBit()) << i
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}
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return
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}
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func (d *Demuxer) readBits16(n byte) (res uint16) {
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for i := n - 1; i != 255; i-- {
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res |= uint16(d.readBit()) << i
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}
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return
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}
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func (d *Demuxer) readTime() uint32 {
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// https://en.wikipedia.org/wiki/Packetized_elementary_stream
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// xxxxAAAx BBBBBBBB BBBBBBBx CCCCCCCC CCCCCCCx
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_ = d.readBits(4) // 0010b or 0011b or 0001b
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ts := d.readBits(3) << 30
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_ = d.readBits(1) // 1b
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ts |= d.readBits(15) << 15
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_ = d.readBits(1) // 1b
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ts |= d.readBits(15)
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_ = d.readBits(1) // 1b
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return ts
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}
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func (d *Demuxer) bytes() []byte {
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return d.buf[d.pos:PacketSize]
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}
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func (d *Demuxer) left() byte {
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return d.end - d.pos
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}
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func (d *Demuxer) setSize(size byte) {
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d.end = d.pos + size
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}
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const (
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PacketSize = 188
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SyncByte = 0x47 // Uppercase G
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ClockRate = 90000 // fixed clock rate for PTS/DTS of any type
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)
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// https://en.wikipedia.org/wiki/Program-specific_information#Elementary_stream_types
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const (
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StreamTypeMetadata = 0 // Reserved
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StreamTypePrivate = 0x06 // PCMU or PCMA or FLAC from FFmpeg
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StreamTypeAAC = 0x0F
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StreamTypeH264 = 0x1B
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StreamTypeH265 = 0x24
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StreamTypePCMATapo = 0x90
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StreamTypePrivateOPUS = 0xEB
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)
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// PES - Packetized Elementary Stream
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type PES struct {
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StreamID byte // from each PES header
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StreamType byte // from PMT table
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Sequence uint16 // manual
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Timestamp uint32 // manual
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PTS uint32 // from extra header, always 90000Hz
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DTS uint32
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Payload []byte // from PES body
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Size int // from PES header, can be 0
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wr *bits.Writer
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}
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func (p *PES) SetBuffer(size uint16, b []byte) {
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p.Payload = make([]byte, 0, size)
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p.Payload = append(p.Payload, b...)
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p.Size = int(size)
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}
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func (p *PES) AppendBuffer(b []byte) {
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p.Payload = append(p.Payload, b...)
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}
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func (p *PES) GetPacket() (pkt *rtp.Packet) {
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switch p.StreamType {
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case StreamTypeH264, StreamTypeH265:
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pkt = &rtp.Packet{
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Header: rtp.Header{
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PayloadType: p.StreamType,
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},
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Payload: annexb.EncodeToAVCC(p.Payload),
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}
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if p.DTS != 0 {
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pkt.Timestamp = p.DTS
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// wrong place for CTS, but we don't have another one
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pkt.ExtensionProfile = uint16(p.PTS - p.DTS)
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} else {
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pkt.Timestamp = p.PTS
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}
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case StreamTypeAAC:
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p.Sequence++
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pkt = &rtp.Packet{
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Header: rtp.Header{
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Version: 2,
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Marker: true,
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PayloadType: p.StreamType,
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SequenceNumber: p.Sequence,
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Timestamp: p.PTS,
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//Timestamp: p.Timestamp,
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},
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Payload: aac.ADTStoRTP(p.Payload),
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}
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//p.Timestamp += aac.RTPTimeSize(pkt.Payload) // update next timestamp!
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case StreamTypePCMATapo:
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p.Sequence++
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pkt = &rtp.Packet{
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Header: rtp.Header{
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Version: 2,
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Marker: true,
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PayloadType: p.StreamType,
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SequenceNumber: p.Sequence,
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Timestamp: p.PTS,
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//Timestamp: p.Timestamp,
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},
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Payload: p.Payload,
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}
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//p.Timestamp += uint32(len(p.Payload)) // update next timestamp!
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case StreamTypePrivateOPUS:
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p.Sequence++
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pkt = &rtp.Packet{
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Header: rtp.Header{
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Version: 2,
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Marker: true,
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PayloadType: p.StreamType,
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SequenceNumber: p.Sequence,
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Timestamp: p.PTS,
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},
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}
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pkt.Payload, p.Payload = CutOPUSPacket(p.Payload)
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p.PTS += opusDT
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return
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}
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p.Payload = nil
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return
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}
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