-
Notifications
You must be signed in to change notification settings - Fork 50
/
jitter_buffer.go
282 lines (251 loc) · 7.84 KB
/
jitter_buffer.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
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT
// Package jitterbuffer implements a buffer for RTP packets designed to help
// counteract non-deterministic sources of latency
package jitterbuffer
import (
"errors"
"math"
"sync"
"github.com/pion/rtp"
)
// State tracks a JitterBuffer as either Buffering or Emitting
type State uint16
// Event represents all events a JitterBuffer can emit
type Event string
var (
// ErrBufferUnderrun is returned when the buffer has no items
ErrBufferUnderrun = errors.New("invalid Peek: Empty jitter buffer")
// ErrPopWhileBuffering is returned if a jitter buffer is not in a playback state
ErrPopWhileBuffering = errors.New("attempt to pop while buffering")
)
const (
// Buffering is the state when the jitter buffer has not started emitting yet, or has hit an underflow and needs to re-buffer packets
Buffering State = iota
// Emitting is the state when the jitter buffer is operating nominally
Emitting
)
const (
// StartBuffering is emitted when the buffer receives its first packet
StartBuffering Event = "startBuffering"
// BeginPlayback is emitted when the buffer has satisfied its buffer length
BeginPlayback = "playing"
// BufferUnderflow is emitted when the buffer does not have enough packets to Pop
BufferUnderflow = "underflow"
// BufferOverflow is emitted when the buffer has exceeded its limit
BufferOverflow = "overflow"
)
func (jbs State) String() string {
switch jbs {
case Buffering:
return "Buffering"
case Emitting:
return "Emitting"
}
return "unknown"
}
type (
// Option will Override JitterBuffer's defaults
Option func(jb *JitterBuffer)
// EventListener will be called when the corresponding Event occurs
EventListener func(event Event, jb *JitterBuffer)
)
// A JitterBuffer will accept Pushed packets, put them in sequence number
// order, and allows removing in either sequence number order or via a
// provided timestamp
type JitterBuffer struct {
packets *PriorityQueue
minStartCount uint16
lastSequence uint16
playoutHead uint16
playoutReady bool
state State
stats Stats
listeners map[Event][]EventListener
mutex sync.Mutex
}
// Stats Track interesting statistics for the life of this JitterBuffer
// outOfOrderCount will provide the number of times a packet was Pushed
//
// without its predecessor being present
//
// underflowCount will provide the count of attempts to Pop an empty buffer
// overflowCount will track the number of times the jitter buffer exceeds its limit
type Stats struct {
outOfOrderCount uint32
underflowCount uint32
overflowCount uint32
}
// New will initialize a jitter buffer and its associated statistics
func New(opts ...Option) *JitterBuffer {
jb := &JitterBuffer{
state: Buffering,
stats: Stats{0, 0, 0},
minStartCount: 50,
packets: NewQueue(),
listeners: make(map[Event][]EventListener),
}
for _, o := range opts {
o(jb)
}
return jb
}
// WithMinimumPacketCount will set the required number of packets to be received before
// any attempt to pop a packet can succeed
func WithMinimumPacketCount(count uint16) Option {
return func(jb *JitterBuffer) {
jb.minStartCount = count
}
}
// Listen will register an event listener
// The jitter buffer may emit events correspnding, interested listerns should
// look at Event for available events
func (jb *JitterBuffer) Listen(event Event, cb EventListener) {
jb.listeners[event] = append(jb.listeners[event], cb)
}
// PlayoutHead returns the SequenceNumber that will be attempted to Pop next
func (jb *JitterBuffer) PlayoutHead() uint16 {
jb.mutex.Lock()
defer jb.mutex.Unlock()
return jb.playoutHead
}
// SetPlayoutHead allows you to manually specify the packet you wish to pop next
// If you have encountered a packet that hasn't resolved you can skip it
func (jb *JitterBuffer) SetPlayoutHead(playoutHead uint16) {
jb.mutex.Lock()
defer jb.mutex.Unlock()
jb.playoutHead = playoutHead
}
func (jb *JitterBuffer) updateStats(lastPktSeqNo uint16) {
// If we have at least one packet, and the next packet being pushed in is not
// at the expected sequence number increment the out of order count
if jb.packets.Length() > 0 && lastPktSeqNo != ((jb.lastSequence+1)%math.MaxUint16) {
jb.stats.outOfOrderCount++
}
jb.lastSequence = lastPktSeqNo
}
// Push an RTP packet into the jitter buffer, this does not clone
// the data so if the memory is expected to be reused, the caller should
// take this in to account and pass a copy of the packet they wish to buffer
func (jb *JitterBuffer) Push(packet *rtp.Packet) {
jb.mutex.Lock()
defer jb.mutex.Unlock()
if jb.packets.Length() == 0 {
jb.emit(StartBuffering)
}
if jb.packets.Length() > 100 {
jb.stats.overflowCount++
jb.emit(BufferOverflow)
}
if !jb.playoutReady && jb.packets.Length() == 0 {
jb.playoutHead = packet.SequenceNumber
}
jb.updateStats(packet.SequenceNumber)
jb.packets.Push(packet, packet.SequenceNumber)
jb.updateState()
}
func (jb *JitterBuffer) emit(event Event) {
for _, l := range jb.listeners[event] {
l(event, jb)
}
}
func (jb *JitterBuffer) updateState() {
// For now, we only look at the number of packets captured in the play buffer
if jb.packets.Length() >= jb.minStartCount && jb.state == Buffering {
jb.state = Emitting
jb.playoutReady = true
jb.emit(BeginPlayback)
}
}
// Peek at the packet which is either:
//
// At the playout head when we are emitting, and the playoutHead flag is true
//
// or else
//
// At the last sequence received
func (jb *JitterBuffer) Peek(playoutHead bool) (*rtp.Packet, error) {
jb.mutex.Lock()
defer jb.mutex.Unlock()
if jb.packets.Length() < 1 {
return nil, ErrBufferUnderrun
}
if playoutHead && jb.state == Emitting {
return jb.packets.Find(jb.playoutHead)
}
return jb.packets.Find(jb.lastSequence)
}
// Pop an RTP packet from the jitter buffer at the current playout head
func (jb *JitterBuffer) Pop() (*rtp.Packet, error) {
jb.mutex.Lock()
defer jb.mutex.Unlock()
if jb.state != Emitting {
return nil, ErrPopWhileBuffering
}
packet, err := jb.packets.PopAt(jb.playoutHead)
if err != nil {
jb.stats.underflowCount++
jb.emit(BufferUnderflow)
return nil, err
}
jb.playoutHead = (jb.playoutHead + 1) % math.MaxUint16
jb.updateState()
return packet, nil
}
// PopAtSequence will pop an RTP packet from the jitter buffer at the specified Sequence
func (jb *JitterBuffer) PopAtSequence(sq uint16) (*rtp.Packet, error) {
jb.mutex.Lock()
defer jb.mutex.Unlock()
if jb.state != Emitting {
return nil, ErrPopWhileBuffering
}
packet, err := jb.packets.PopAt(sq)
if err != nil {
jb.stats.underflowCount++
jb.emit(BufferUnderflow)
return nil, err
}
jb.playoutHead = (jb.playoutHead + 1) % math.MaxUint16
jb.updateState()
return packet, nil
}
// PeekAtSequence will return an RTP packet from the jitter buffer at the specified Sequence
// without removing it from the buffer
func (jb *JitterBuffer) PeekAtSequence(sq uint16) (*rtp.Packet, error) {
jb.mutex.Lock()
defer jb.mutex.Unlock()
packet, err := jb.packets.Find(sq)
if err != nil {
return nil, err
}
return packet, nil
}
// PopAtTimestamp pops an RTP packet from the jitter buffer with the provided timestamp
// Call this method repeatedly to drain the buffer at the timestamp
func (jb *JitterBuffer) PopAtTimestamp(ts uint32) (*rtp.Packet, error) {
jb.mutex.Lock()
defer jb.mutex.Unlock()
if jb.state != Emitting {
return nil, ErrPopWhileBuffering
}
packet, err := jb.packets.PopAtTimestamp(ts)
if err != nil {
jb.stats.underflowCount++
jb.emit(BufferUnderflow)
return nil, err
}
jb.updateState()
return packet, nil
}
// Clear will empty the buffer and optionally reset the state
func (jb *JitterBuffer) Clear(resetState bool) {
jb.mutex.Lock()
defer jb.mutex.Unlock()
jb.packets.Clear()
if resetState {
jb.lastSequence = 0
jb.state = Buffering
jb.stats = Stats{0, 0, 0}
jb.minStartCount = 50
}
}