forked from bluenviron/gortsplib
-
Notifications
You must be signed in to change notification settings - Fork 0
/
encoder.go
196 lines (162 loc) · 3.97 KB
/
encoder.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
package rtpmpeg1audio
import (
"crypto/rand"
"github.com/bluenviron/mediacommon/pkg/codecs/mpeg1audio"
"github.com/pion/rtp"
)
const (
rtpVersion = 2
defaultPayloadMaxSize = 1460 // 1500 (UDP MTU) - 20 (IP header) - 8 (UDP header) - 12 (RTP header)
)
func randUint32() (uint32, error) {
var b [4]byte
_, err := rand.Read(b[:])
if err != nil {
return 0, err
}
return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3]), nil
}
func lenAggregated(frames [][]byte, frame []byte) int {
n := 4 + len(frame)
for _, fr := range frames {
n += len(fr)
}
return n
}
func packetCount(avail, le int) int {
n := le / avail
if (le % avail) != 0 {
n++
}
return n
}
// Encoder is a RTP/MPEG-1/2 Audio encoder.
// Specification: https://datatracker.ietf.org/doc/html/rfc2250
type Encoder struct {
// SSRC of packets (optional).
// It defaults to a random value.
SSRC *uint32
// initial sequence number of packets (optional).
// It defaults to a random value.
InitialSequenceNumber *uint16
// maximum size of packet payloads (optional).
// It defaults to 1460.
PayloadMaxSize int
sequenceNumber uint16
}
// Init initializes the encoder.
func (e *Encoder) Init() error {
if e.SSRC == nil {
v, err := randUint32()
if err != nil {
return err
}
e.SSRC = &v
}
if e.InitialSequenceNumber == nil {
v, err := randUint32()
if err != nil {
return err
}
v2 := uint16(v)
e.InitialSequenceNumber = &v2
}
if e.PayloadMaxSize == 0 {
e.PayloadMaxSize = defaultPayloadMaxSize
}
e.sequenceNumber = *e.InitialSequenceNumber
return nil
}
// Encode encodes frames into RTP packets.
func (e *Encoder) Encode(frames [][]byte) ([]*rtp.Packet, error) {
var rets []*rtp.Packet
var batch [][]byte
timestamp := uint32(0)
for _, frame := range frames {
if lenAggregated(batch, frame) <= e.PayloadMaxSize {
batch = append(batch, frame)
} else {
// write current batch
if batch != nil {
pkts, err := e.writeBatch(batch, timestamp)
if err != nil {
return nil, err
}
rets = append(rets, pkts...)
for _, frame := range batch {
var h mpeg1audio.FrameHeader
err := h.Unmarshal(frame)
if err != nil {
return nil, err
}
timestamp += uint32(h.SampleCount())
}
}
// initialize new batch
batch = [][]byte{frame}
}
}
// write last batch
pkts, err := e.writeBatch(batch, timestamp)
if err != nil {
return nil, err
}
rets = append(rets, pkts...)
return rets, nil
}
func (e *Encoder) writeBatch(frames [][]byte, timestamp uint32) ([]*rtp.Packet, error) {
if len(frames) != 1 || lenAggregated(frames, nil) < e.PayloadMaxSize {
return e.writeAggregated(frames, timestamp)
}
return e.writeFragmented(frames[0], timestamp)
}
func (e *Encoder) writeFragmented(frame []byte, timestamp uint32) ([]*rtp.Packet, error) {
avail := e.PayloadMaxSize - 4
le := len(frame)
packetCount := packetCount(avail, le)
ret := make([]*rtp.Packet, packetCount)
pos := 0
le = avail
for i := range ret {
if i == (packetCount - 1) {
le = len(frame) - pos
}
payload := make([]byte, 4+le)
payload[2] = byte(pos >> 8)
payload[3] = byte(pos)
pos += copy(payload[4:], frame[pos:])
ret[i] = &rtp.Packet{
Header: rtp.Header{
Version: rtpVersion,
PayloadType: 14,
SequenceNumber: e.sequenceNumber,
Timestamp: timestamp,
SSRC: *e.SSRC,
Marker: true,
},
Payload: payload,
}
e.sequenceNumber++
}
return ret, nil
}
func (e *Encoder) writeAggregated(frames [][]byte, timestamp uint32) ([]*rtp.Packet, error) {
payload := make([]byte, lenAggregated(frames, nil))
n := 4
for _, frame := range frames {
n += copy(payload[n:], frame)
}
pkt := &rtp.Packet{
Header: rtp.Header{
Version: rtpVersion,
PayloadType: 14,
SequenceNumber: e.sequenceNumber,
Timestamp: timestamp,
SSRC: *e.SSRC,
Marker: true,
},
Payload: payload,
}
e.sequenceNumber++
return []*rtp.Packet{pkt}, nil
}