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Merged
dennwc merged 1 commit into from
Aug 28, 2026
Merged

Match audio sample rate for DTMF. #82

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30 changes: 16 additions & 14 deletions dtmf/dtmf.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ package dtmf
import (
"context"
"encoding/binary"
"fmt"
"io"
"math"
"time"
Expand All @@ -27,19 +28,20 @@ import (
)

const (
SDPNameOnly = "telephone-event"
SDPNameAndRate = SDPNameOnly + "/8000"
SDPName = SDPNameAndRate // Deprecated: use SDPNameOnly or SDPNameAndRate
SDPNameOnly = "telephone-event"
)
const SampleRate = 8000

func init() {
media.RegisterCodec(media.NewCodec(media.CodecInfo{
SDPName: SDPNameAndRate,
SampleRate: SampleRate,
RTPIsStatic: false,
Priority: -100, // let it be last in SDP
}))
for i, rate := range []int{
8000, 16000, 48000,
} {
media.RegisterCodec(media.NewCodec(media.CodecInfo{
SDPName: fmt.Sprintf("%s/%d", SDPNameOnly, rate),
SampleRate: rate,
RTPIsStatic: false,
Priority: -100 - i, // let it be last in SDP
}))
}
}

const (
Expand Down Expand Up @@ -219,7 +221,7 @@ func Encode(out []byte, ev Event) (int, error) {
// Write in-band (analog) and off-band (digital) DTMF tones to audio and RTP streams respectively.
//
// Digits may contain a special character 'w' which adds a 0.5 sec delay.
func Write(ctx context.Context, audio media.Writer[media.PCM16Sample], events *rtp.Stream, startTs uint32, digits string) error {
func Write(ctx context.Context, audio media.Writer[media.PCM16Sample], events *rtp.Stream, eventsRate int, startTs uint32, digits string) error {
const framesPerSec = int(time.Second / rtp.DefFrameDur)
var (
buf [4]byte
Expand Down Expand Up @@ -247,7 +249,7 @@ func Write(ctx context.Context, audio media.Writer[media.PCM16Sample], events *r
totalDur = dt
nextDelay = 0
if events != nil {
events.Delay(uint32(dt / (time.Second / SampleRate)))
events.Delay(uint32(dt / (time.Second / time.Duration(eventsRate))))
}
}

Expand Down Expand Up @@ -303,7 +305,7 @@ func Write(ctx context.Context, audio media.Writer[media.PCM16Sample], events *r
n, err := Encode(buf[:], Event{
Code: code,
Volume: eventVolume,
Dur: uint16(dur / (time.Second / SampleRate)),
Dur: uint16(dur / (time.Second / time.Duration(eventsRate))),
End: end,
})
if err != nil {
Expand All @@ -323,7 +325,7 @@ func Write(ctx context.Context, audio media.Writer[media.PCM16Sample], events *r
return err
}
// advance the timestamp now
events.Delay(uint32(totalDur / (time.Second / SampleRate)))
events.Delay(uint32(totalDur / (time.Second / time.Duration(eventsRate))))
}
}
remaining -= step
Expand Down
157 changes: 81 additions & 76 deletions dtmf/dtmf_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ package dtmf
import (
"context"
"encoding/hex"
"strconv"
"testing"
"time"

Expand Down Expand Up @@ -132,83 +133,87 @@ func TestDecodeRTPWithEnd(t *testing.T) {
func TestDTMFDelay(t *testing.T) {
const startTime = 1242

var buf rtp.Buffer
w := rtp.NewSeqWriter(&buf).NewStream(101, SampleRate)
err := Write(context.Background(), nil, w, startTime, "1w23")
require.NoError(t, err)
for _, eventsRate := range []int{
8000, 16000,
} {
t.Run(strconv.Itoa(eventsRate), func(t *testing.T) {
var buf rtp.Buffer
w := rtp.NewSeqWriter(&buf).NewStream(101, eventsRate)
err := Write(context.Background(), nil, w, eventsRate, startTime, "1w23")
require.NoError(t, err)

type packet struct {
SequenceNumber uint16
Timestamp uint32
Marker bool
Event
}
var (
exp []packet
seq uint16
ts uint32
)
const (
packetDur = uint32(SampleRate / int(time.Second/rtp.DefFrameDur))
)

ts = startTime

expectDigit := func(code byte, digit byte) {
start := ts
const n = 13
for i := 0; i < n-1; i++ {
exp = append(exp, packet{
SequenceNumber: seq,
Timestamp: start, // should be the same for all events
Marker: i == 0,
Event: Event{
Code: code,
Digit: digit,
Volume: eventVolume,
Dur: uint16(i+1) * uint16(packetDur),
End: false,
},
})
ts += packetDur
seq++
}
// end event must be sent 3 times with the same duration
for i := 0; i < 3; i++ {
exp = append(exp, packet{
SequenceNumber: seq,
Timestamp: start, // should be the same for all events
Marker: false,
Event: Event{
Code: code,
Digit: digit,
Volume: eventVolume,
Dur: uint16(n) * uint16(packetDur),
End: true,
},
})
seq++
}
ts += packetDur
// delay between digits
ts += uint32(eventDur / (time.Second / SampleRate))
// rounding error (12.5 events in a sec)
ts -= packetDur / 2
}
expectDigit(1, '1')
ts += SampleRate / 2 // 500ms delay
expectDigit(2, '2')
expectDigit(3, '3')
var got []packet
for _, p := range buf {
e, err := Decode(p.Payload)
require.NoError(t, err)
got = append(got, packet{
SequenceNumber: p.SequenceNumber,
Timestamp: p.Timestamp,
Marker: p.Marker,
Event: e,
type packet struct {
SequenceNumber uint16
Timestamp uint32
Marker bool
Event
}
var (
exp []packet
seq uint16
ts uint32
)
packetDur := uint32(eventsRate / int(time.Second/rtp.DefFrameDur))

ts = startTime

expectDigit := func(code byte, digit byte) {
start := ts
const n = 13
for i := 0; i < n-1; i++ {
exp = append(exp, packet{
SequenceNumber: seq,
Timestamp: start, // should be the same for all events
Marker: i == 0,
Event: Event{
Code: code,
Digit: digit,
Volume: eventVolume,
Dur: uint16(i+1) * uint16(packetDur),
End: false,
},
})
ts += packetDur
seq++
}
// end event must be sent 3 times with the same duration
for i := 0; i < 3; i++ {
exp = append(exp, packet{
SequenceNumber: seq,
Timestamp: start, // should be the same for all events
Marker: false,
Event: Event{
Code: code,
Digit: digit,
Volume: eventVolume,
Dur: uint16(n) * uint16(packetDur),
End: true,
},
})
seq++
}
ts += packetDur
// delay between digits
ts += uint32(eventDur / (time.Second / time.Duration(eventsRate)))
// rounding error (12.5 events in a sec)
ts -= packetDur / 2
}
expectDigit(1, '1')
ts += uint32(eventsRate) / 2 // 500ms delay
expectDigit(2, '2')
expectDigit(3, '3')
var got []packet
for _, p := range buf {
e, err := Decode(p.Payload)
require.NoError(t, err)
got = append(got, packet{
SequenceNumber: p.SequenceNumber,
Timestamp: p.Timestamp,
Marker: p.Marker,
Event: e,
})
}
require.Equal(t, exp, got)
})
}
require.Equal(t, exp, got)
}
4 changes: 2 additions & 2 deletions resample_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -195,8 +195,8 @@ func memstats(pid int) int64 {
}

func TestResampleLeak(t *testing.T) {
if runtime.GOOS == "windows" {
t.Skip("windows is not supported for this test")
if runtime.GOOS != "linux" {
t.Skip("only linux supported for this test")
}
pid := os.Getpid()

Expand Down
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