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rtp.go
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rtp.go
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package mjpeg
import (
"bytes"
"encoding/binary"
"github.com/AlexxIT/go2rtc/pkg/core"
"github.com/pion/rtp"
"image"
"image/jpeg"
)
func RTPDepay(handlerFunc core.HandlerFunc) core.HandlerFunc {
buf := make([]byte, 0, 512*1024) // 512K
return func(packet *rtp.Packet) {
//log.Printf("[RTP] codec: %s, size: %6d, ts: %10d, pt: %2d, ssrc: %d, seq: %d, mark: %v", track.Codec.Name, len(packet.Payload), packet.Timestamp, packet.PayloadType, packet.SSRC, packet.SequenceNumber, packet.Marker)
// https://www.rfc-editor.org/rfc/rfc2435#section-3.1
b := packet.Payload
// 3.1. JPEG header
t := b[4]
// 3.1.7. Restart Marker header
if 64 <= t && t <= 127 {
b = b[12:] // skip it
} else {
b = b[8:]
}
if len(buf) == 0 {
var lqt, cqt []byte
// 3.1.8. Quantization Table header
q := packet.Payload[5]
if q >= 128 {
lqt = b[4:68]
cqt = b[68:132]
b = b[132:]
} else {
lqt, cqt = MakeTables(q)
}
// https://www.rfc-editor.org/rfc/rfc2435#section-3.1.5
// The maximum width is 2040 pixels.
w := uint16(packet.Payload[6]) << 3
h := uint16(packet.Payload[7]) << 3
// fix sizes more than 2040
switch {
// 512x1920 512x1440
case w == cutSize(2560) && (h == 1920 || h == 1440):
w = 2560
// 1792x112
case w == cutSize(3840) && h == cutSize(2160):
w = 3840
h = 2160
// 256x1296
case w == cutSize(2304) && h == 1296:
w = 2304
}
//fmt.Printf("t: %d, q: %d, w: %d, h: %d\n", t, q, w, h)
buf = MakeHeaders(buf, t, w, h, lqt, cqt)
}
// 3.1.9. JPEG Payload
buf = append(buf, b...)
if !packet.Marker {
return
}
if end := buf[len(buf)-2:]; end[0] != 0xFF && end[1] != 0xD9 {
buf = append(buf, 0xFF, 0xD9)
}
clone := *packet
clone.Payload = buf
buf = buf[:0] // clear buffer
handlerFunc(&clone)
}
}
func cutSize(size uint16) uint16 {
return ((size >> 3) & 0xFF) << 3
}
func RTPPay(handlerFunc core.HandlerFunc) core.HandlerFunc {
const packetSize = 1436
sequencer := rtp.NewRandomSequencer()
return func(packet *rtp.Packet) {
// reincode image to more common form
p, err := Transcode(packet.Payload)
if err != nil {
return
}
h1 := make([]byte, 8)
h1[4] = 1 // Type
h1[5] = 255 // Q
// MBZ=0, Precision=0, Length=128
h2 := make([]byte, 4, 132)
h2[3] = 128
var jpgData []byte
for jpgData == nil {
// 2 bytes h1
if p[0] != 0xFF {
return
}
size := binary.BigEndian.Uint16(p[2:]) + 2
// 2 bytes payload size (include 2 bytes)
switch p[1] {
case 0xD8: // 0. Start Of Image (size=0)
p = p[2:]
continue
case 0xDB: // 1. Define Quantization Table (size=130)
for i := uint16(4 + 1); i < size; i += 1 + 64 {
h2 = append(h2, p[i:i+64]...)
}
case 0xC0: // 2. Start Of Frame (size=15)
if p[4] != 8 {
return
}
h := binary.BigEndian.Uint16(p[5:])
w := binary.BigEndian.Uint16(p[7:])
h1[6] = uint8(w >> 3)
h1[7] = uint8(h >> 3)
case 0xC4: // 3. Define Huffman Table (size=416)
case 0xDA: // 4. Start Of Scan (size=10)
jpgData = p[size:]
}
p = p[size:]
}
offset := 0
p = make([]byte, 0)
for jpgData != nil {
p = p[:0]
if offset > 0 {
h1[1] = byte(offset >> 16)
h1[2] = byte(offset >> 8)
h1[3] = byte(offset)
p = append(p, h1...)
} else {
p = append(p, h1...)
p = append(p, h2...)
}
dataLen := packetSize - len(p)
if dataLen < len(jpgData) {
p = append(p, jpgData[:dataLen]...)
jpgData = jpgData[dataLen:]
offset += dataLen
} else {
p = append(p, jpgData...)
jpgData = nil
}
clone := rtp.Packet{
Header: rtp.Header{
Version: 2,
Marker: jpgData == nil,
SequenceNumber: sequencer.NextSequenceNumber(),
Timestamp: packet.Timestamp,
},
Payload: p,
}
handlerFunc(&clone)
}
}
}
func Transcode(b []byte) ([]byte, error) {
img, err := jpeg.Decode(bytes.NewReader(b))
if err != nil {
return nil, err
}
wh := img.Bounds().Size()
w := wh.X
h := wh.Y
if w > 2040 {
w = 2040
} else if w&3 > 0 {
w &= 3
}
if h > 2040 {
h = 2040
} else if h&3 > 0 {
h &= 3
}
if w != wh.X || h != wh.Y {
x0 := (wh.X - w) / 2
y0 := (wh.Y - h) / 2
rect := image.Rect(x0, y0, x0+w, y0+h)
img = img.(*image.YCbCr).SubImage(rect)
}
buf := bytes.NewBuffer(nil)
if err = jpeg.Encode(buf, img, nil); err != nil {
return nil, err
}
return buf.Bytes(), nil
}