286 lines
7.3 KiB
Go
286 lines
7.3 KiB
Go
package codecs
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import (
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"encoding/binary"
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"fmt"
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)
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// H264Payloader payloads H264 packets
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type H264Payloader struct {
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spsNalu, ppsNalu []byte
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}
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const (
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stapaNALUType = 24
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fuaNALUType = 28
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fubNALUType = 29
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spsNALUType = 7
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ppsNALUType = 8
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audNALUType = 9
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fillerNALUType = 12
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fuaHeaderSize = 2
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stapaHeaderSize = 1
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stapaNALULengthSize = 2
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naluTypeBitmask = 0x1F
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naluRefIdcBitmask = 0x60
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fuStartBitmask = 0x80
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fuEndBitmask = 0x40
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outputStapAHeader = 0x78
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)
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func annexbNALUStartCode() []byte { return []byte{0x00, 0x00, 0x00, 0x01} }
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func emitNalus(nals []byte, emit func([]byte)) {
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nextInd := func(nalu []byte, start int) (indStart int, indLen int) {
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zeroCount := 0
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for i, b := range nalu[start:] {
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if b == 0 {
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zeroCount++
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continue
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} else if b == 1 {
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if zeroCount >= 2 {
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return start + i - zeroCount, zeroCount + 1
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}
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}
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zeroCount = 0
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}
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return -1, -1
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}
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nextIndStart, nextIndLen := nextInd(nals, 0)
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if nextIndStart == -1 {
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emit(nals)
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} else {
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for nextIndStart != -1 {
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prevStart := nextIndStart + nextIndLen
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nextIndStart, nextIndLen = nextInd(nals, prevStart)
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if nextIndStart != -1 {
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emit(nals[prevStart:nextIndStart])
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} else {
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// Emit until end of stream, no end indicator found
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emit(nals[prevStart:])
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}
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}
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}
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}
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// Payload fragments a H264 packet across one or more byte arrays
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func (p *H264Payloader) Payload(mtu uint16, payload []byte) [][]byte {
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var payloads [][]byte
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if len(payload) == 0 {
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return payloads
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}
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emitNalus(payload, func(nalu []byte) {
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if len(nalu) == 0 {
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return
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}
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naluType := nalu[0] & naluTypeBitmask
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naluRefIdc := nalu[0] & naluRefIdcBitmask
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switch {
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case naluType == audNALUType || naluType == fillerNALUType:
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return
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case naluType == spsNALUType:
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p.spsNalu = nalu
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return
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case naluType == ppsNALUType:
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p.ppsNalu = nalu
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return
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case p.spsNalu != nil && p.ppsNalu != nil:
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// Pack current NALU with SPS and PPS as STAP-A
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spsLen := make([]byte, 2)
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binary.BigEndian.PutUint16(spsLen, uint16(len(p.spsNalu)))
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ppsLen := make([]byte, 2)
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binary.BigEndian.PutUint16(ppsLen, uint16(len(p.ppsNalu)))
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stapANalu := []byte{outputStapAHeader}
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stapANalu = append(stapANalu, spsLen...)
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stapANalu = append(stapANalu, p.spsNalu...)
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stapANalu = append(stapANalu, ppsLen...)
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stapANalu = append(stapANalu, p.ppsNalu...)
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if len(stapANalu) <= int(mtu) {
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out := make([]byte, len(stapANalu))
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copy(out, stapANalu)
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payloads = append(payloads, out)
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}
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p.spsNalu = nil
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p.ppsNalu = nil
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}
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// Single NALU
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if len(nalu) <= int(mtu) {
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out := make([]byte, len(nalu))
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copy(out, nalu)
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payloads = append(payloads, out)
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return
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}
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// FU-A
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maxFragmentSize := int(mtu) - fuaHeaderSize
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// The FU payload consists of fragments of the payload of the fragmented
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// NAL unit so that if the fragmentation unit payloads of consecutive
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// FUs are sequentially concatenated, the payload of the fragmented NAL
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// unit can be reconstructed. The NAL unit type octet of the fragmented
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// NAL unit is not included as such in the fragmentation unit payload,
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// but rather the information of the NAL unit type octet of the
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// fragmented NAL unit is conveyed in the F and NRI fields of the FU
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// indicator octet of the fragmentation unit and in the type field of
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// the FU header. An FU payload MAY have any number of octets and MAY
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// be empty.
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naluData := nalu
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// According to the RFC, the first octet is skipped due to redundant information
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naluDataIndex := 1
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naluDataLength := len(nalu) - naluDataIndex
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naluDataRemaining := naluDataLength
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if min(maxFragmentSize, naluDataRemaining) <= 0 {
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return
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}
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for naluDataRemaining > 0 {
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currentFragmentSize := min(maxFragmentSize, naluDataRemaining)
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out := make([]byte, fuaHeaderSize+currentFragmentSize)
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// +---------------+
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// |0|1|2|3|4|5|6|7|
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// +-+-+-+-+-+-+-+-+
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// |F|NRI| Type |
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// +---------------+
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out[0] = fuaNALUType
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out[0] |= naluRefIdc
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// +---------------+
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// |0|1|2|3|4|5|6|7|
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// +-+-+-+-+-+-+-+-+
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// |S|E|R| Type |
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// +---------------+
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out[1] = naluType
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if naluDataRemaining == naluDataLength {
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// Set start bit
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out[1] |= 1 << 7
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} else if naluDataRemaining-currentFragmentSize == 0 {
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// Set end bit
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out[1] |= 1 << 6
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}
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copy(out[fuaHeaderSize:], naluData[naluDataIndex:naluDataIndex+currentFragmentSize])
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payloads = append(payloads, out)
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naluDataRemaining -= currentFragmentSize
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naluDataIndex += currentFragmentSize
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}
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})
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return payloads
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}
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// H264Packet represents the H264 header that is stored in the payload of an RTP Packet
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type H264Packet struct {
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IsAVC bool
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fuaBuffer []byte
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videoDepacketizer
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}
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func (p *H264Packet) doPackaging(nalu []byte) []byte {
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if p.IsAVC {
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naluLength := make([]byte, 4)
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binary.BigEndian.PutUint32(naluLength, uint32(len(nalu)))
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return append(naluLength, nalu...)
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}
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return append(annexbNALUStartCode(), nalu...)
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}
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// IsDetectedFinalPacketInSequence returns true of the packet passed in has the
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// marker bit set indicated the end of a packet sequence
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func (p *H264Packet) IsDetectedFinalPacketInSequence(rtpPacketMarketBit bool) bool {
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return rtpPacketMarketBit
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}
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// Unmarshal parses the passed byte slice and stores the result in the H264Packet this method is called upon
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func (p *H264Packet) Unmarshal(payload []byte) ([]byte, error) {
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if payload == nil {
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return nil, errNilPacket
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} else if len(payload) <= 2 {
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return nil, fmt.Errorf("%w: %d <= 2", errShortPacket, len(payload))
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}
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// NALU Types
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// https://tools.ietf.org/html/rfc6184#section-5.4
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naluType := payload[0] & naluTypeBitmask
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switch {
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case naluType > 0 && naluType < 24:
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return p.doPackaging(payload), nil
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case naluType == stapaNALUType:
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currOffset := int(stapaHeaderSize)
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result := []byte{}
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for currOffset < len(payload) {
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naluSize := int(binary.BigEndian.Uint16(payload[currOffset:]))
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currOffset += stapaNALULengthSize
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if len(payload) < currOffset+naluSize {
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return nil, fmt.Errorf("%w STAP-A declared size(%d) is larger than buffer(%d)", errShortPacket, naluSize, len(payload)-currOffset)
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}
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result = append(result, p.doPackaging(payload[currOffset:currOffset+naluSize])...)
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currOffset += naluSize
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}
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return result, nil
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case naluType == fuaNALUType:
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if len(payload) < fuaHeaderSize {
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return nil, errShortPacket
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}
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if p.fuaBuffer == nil {
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p.fuaBuffer = []byte{}
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}
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p.fuaBuffer = append(p.fuaBuffer, payload[fuaHeaderSize:]...)
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if payload[1]&fuEndBitmask != 0 {
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naluRefIdc := payload[0] & naluRefIdcBitmask
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fragmentedNaluType := payload[1] & naluTypeBitmask
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nalu := append([]byte{}, naluRefIdc|fragmentedNaluType)
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nalu = append(nalu, p.fuaBuffer...)
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p.fuaBuffer = nil
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return p.doPackaging(nalu), nil
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}
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return []byte{}, nil
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}
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return nil, fmt.Errorf("%w: %d", errUnhandledNALUType, naluType)
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}
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// H264PartitionHeadChecker is obsolete
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type H264PartitionHeadChecker struct{}
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// IsPartitionHead checks if this is the head of a packetized nalu stream.
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func (*H264Packet) IsPartitionHead(payload []byte) bool {
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if len(payload) < 2 {
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return false
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}
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if payload[0]&naluTypeBitmask == fuaNALUType ||
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payload[0]&naluTypeBitmask == fubNALUType {
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return payload[1]&fuStartBitmask != 0
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}
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return true
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}
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