status-go/vendor/github.com/pion/rtp/codecs/vp8_packet.go

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2022-03-10 09:44:48 +00:00
package codecs
// VP8Payloader payloads VP8 packets
type VP8Payloader struct {
EnablePictureID bool
pictureID uint16
}
const (
vp8HeaderSize = 1
)
// Payload fragments a VP8 packet across one or more byte arrays
func (p *VP8Payloader) Payload(mtu uint16, payload []byte) [][]byte {
/*
* https://tools.ietf.org/html/rfc7741#section-4.2
*
* 0 1 2 3 4 5 6 7
* +-+-+-+-+-+-+-+-+
* |X|R|N|S|R| PID | (REQUIRED)
* +-+-+-+-+-+-+-+-+
* X: |I|L|T|K| RSV | (OPTIONAL)
* +-+-+-+-+-+-+-+-+
* I: |M| PictureID | (OPTIONAL)
* +-+-+-+-+-+-+-+-+
* L: | TL0PICIDX | (OPTIONAL)
* +-+-+-+-+-+-+-+-+
* T/K: |TID|Y| KEYIDX | (OPTIONAL)
* +-+-+-+-+-+-+-+-+
* S: Start of VP8 partition. SHOULD be set to 1 when the first payload
* octet of the RTP packet is the beginning of a new VP8 partition,
* and MUST NOT be 1 otherwise. The S bit MUST be set to 1 for the
* first packet of each encoded frame.
*/
usingHeaderSize := vp8HeaderSize
if p.EnablePictureID {
switch {
case p.pictureID == 0:
case p.pictureID < 128:
usingHeaderSize = vp8HeaderSize + 2
default:
usingHeaderSize = vp8HeaderSize + 3
}
}
maxFragmentSize := int(mtu) - usingHeaderSize
payloadData := payload
payloadDataRemaining := len(payload)
payloadDataIndex := 0
var payloads [][]byte
// Make sure the fragment/payload size is correct
if min(maxFragmentSize, payloadDataRemaining) <= 0 {
return payloads
}
first := true
for payloadDataRemaining > 0 {
currentFragmentSize := min(maxFragmentSize, payloadDataRemaining)
out := make([]byte, usingHeaderSize+currentFragmentSize)
if first {
out[0] = 0x10
first = false
}
if p.EnablePictureID {
switch usingHeaderSize {
case vp8HeaderSize:
case vp8HeaderSize + 2:
out[0] |= 0x80
out[1] |= 0x80
out[2] |= uint8(p.pictureID & 0x7F)
case vp8HeaderSize + 3:
out[0] |= 0x80
out[1] |= 0x80
out[2] |= 0x80 | uint8((p.pictureID>>8)&0x7F)
out[3] |= uint8(p.pictureID & 0xFF)
}
}
copy(out[usingHeaderSize:], payloadData[payloadDataIndex:payloadDataIndex+currentFragmentSize])
payloads = append(payloads, out)
payloadDataRemaining -= currentFragmentSize
payloadDataIndex += currentFragmentSize
}
p.pictureID++
p.pictureID &= 0x7FFF
return payloads
}
// VP8Packet represents the VP8 header that is stored in the payload of an RTP Packet
type VP8Packet struct {
// Required Header
X uint8 /* extended control bits present */
N uint8 /* when set to 1 this frame can be discarded */
S uint8 /* start of VP8 partition */
PID uint8 /* partition index */
// Extended control bits
I uint8 /* 1 if PictureID is present */
L uint8 /* 1 if TL0PICIDX is present */
T uint8 /* 1 if TID is present */
K uint8 /* 1 if KEYIDX is present */
// Optional extension
PictureID uint16 /* 8 or 16 bits, picture ID */
TL0PICIDX uint8 /* 8 bits temporal level zero index */
TID uint8 /* 2 bits temporal layer index */
Y uint8 /* 1 bit layer sync bit */
KEYIDX uint8 /* 5 bits temporal key frame index */
Payload []byte
videoDepacketizer
}
// Unmarshal parses the passed byte slice and stores the result in the VP8Packet this method is called upon
func (p *VP8Packet) Unmarshal(payload []byte) ([]byte, error) {
if payload == nil {
return nil, errNilPacket
}
payloadLen := len(payload)
if payloadLen < 4 {
return nil, errShortPacket
}
payloadIndex := 0
p.X = (payload[payloadIndex] & 0x80) >> 7
p.N = (payload[payloadIndex] & 0x20) >> 5
p.S = (payload[payloadIndex] & 0x10) >> 4
p.PID = payload[payloadIndex] & 0x07
payloadIndex++
if p.X == 1 {
p.I = (payload[payloadIndex] & 0x80) >> 7
p.L = (payload[payloadIndex] & 0x40) >> 6
p.T = (payload[payloadIndex] & 0x20) >> 5
p.K = (payload[payloadIndex] & 0x10) >> 4
payloadIndex++
}
if p.I == 1 { // PID present?
if payload[payloadIndex]&0x80 > 0 { // M == 1, PID is 16bit
p.PictureID = (uint16(payload[payloadIndex]&0x7F) << 8) | uint16(payload[payloadIndex+1])
payloadIndex += 2
} else {
p.PictureID = uint16(payload[payloadIndex])
payloadIndex++
}
}
if payloadIndex >= payloadLen {
return nil, errShortPacket
}
if p.L == 1 {
p.TL0PICIDX = payload[payloadIndex]
payloadIndex++
}
if payloadIndex >= payloadLen {
return nil, errShortPacket
}
if p.T == 1 || p.K == 1 {
if p.T == 1 {
p.TID = payload[payloadIndex] >> 6
p.Y = (payload[payloadIndex] >> 5) & 0x1
}
if p.K == 1 {
p.KEYIDX = payload[payloadIndex] & 0x1F
}
payloadIndex++
}
if payloadIndex >= payloadLen {
return nil, errShortPacket
}
p.Payload = payload[payloadIndex:]
return p.Payload, nil
}
// VP8PartitionHeadChecker is obsolete
type VP8PartitionHeadChecker struct{}
// IsPartitionHead checks whether if this is a head of the VP8 partition
func (*VP8Packet) IsPartitionHead(payload []byte) bool {
if len(payload) < 1 {
return false
}
return (payload[0] & 0x10) != 0
}