/
main.go
220 lines (187 loc) · 4.11 KB
/
main.go
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package main
import (
"fmt"
"sync"
"time"
"github.com/yobert/alsa"
)
func main() {
cards, err := alsa.OpenCards()
if err != nil {
fmt.Println(err)
return
}
defer alsa.CloseCards(cards)
var (
record_device *alsa.Device
playback_device *alsa.Device
)
// just use the "first" playback and record devices
for _, card := range cards {
devices, err := card.Devices()
if err != nil {
fmt.Println(err)
return
}
for _, device := range devices {
if device.Type != alsa.PCM {
continue
}
if device.Play && playback_device == nil {
playback_device = device
}
if device.Record && record_device == nil {
record_device = device
}
}
}
err = echoback(record_device, playback_device, time.Second*5)
if err != nil {
fmt.Println(err)
return
}
return
}
func echoback(rec, play *alsa.Device, delay time.Duration) error {
var err error
if err = rec.Open(); err != nil {
return err
}
defer rec.Close()
if err = play.Open(); err != nil {
return err
}
defer play.Close()
play.Debug(true)
channels, err := rec.NegotiateChannels(2)
if err != nil {
return err
}
_, err = play.NegotiateChannels(channels)
if err != nil {
return err
}
rate, err := rec.NegotiateRate(44100)
if err != nil {
return err
}
_, err = play.NegotiateRate(rate)
if err != nil {
return err
}
format, err := rec.NegotiateFormat(alsa.S32_LE)
if err != nil {
return err
}
_, err = play.NegotiateFormat(format)
if err != nil {
return err
}
buffer_size, err := rec.NegotiateBufferSize(8192, 16384)
if err != nil {
return err
}
_, err = play.NegotiateBufferSize(buffer_size)
if err != nil {
return err
}
if err = rec.Prepare(); err != nil {
return err
}
if err = play.Prepare(); err != nil {
return err
}
bytes_per_frame := rec.BytesPerFrame()
fmt.Printf("Negotiated parameters: %d channels, %d hz, %v, %d frame buffer, %d bytes per frame\n",
channels, rate, format, buffer_size, bytes_per_frame)
delay_bytes := int(float64(rate) * float64(bytes_per_frame) * delay.Seconds())
buffer_bytes := bytes_per_frame * buffer_size
// a sloppy circular buffer shared between reader and
// writer goroutines
buf := make([]byte,
delay_bytes+
// enough additional space for a read and a write
(buffer_size*2*bytes_per_frame))
fmt.Println("buffer_bytes\t", buffer_bytes)
fmt.Println("delay_bytes\t", delay_bytes)
fmt.Println("len(buf)\t", len(buf))
var cursor_mu sync.Mutex
rec_cursor := 0
play_cursor := 0
go func() {
for {
cursor_mu.Lock()
avail := play_cursor - rec_cursor
if avail <= 0 {
avail = len(buf) - rec_cursor
if avail == 0 && play_cursor > 0 {
// loop around
rec_cursor = 0
avail = play_cursor
}
}
if avail > buffer_bytes {
// cap read size to alsa buffer size
avail = buffer_bytes
}
rc := rec_cursor
cursor_mu.Unlock()
if avail == 0 {
fmt.Println(" rec: waiting")
time.Sleep(time.Millisecond * 100)
continue
}
fmt.Println("reading...")
err := rec.Read(buf[rc : rc+avail])
if err != nil {
fmt.Println(err)
return
}
cursor_mu.Lock()
rec_cursor += avail
if rec_cursor == len(buf) {
rec_cursor = 0
} else if rec_cursor > len(buf) {
panic("wtf, rec cursor overrun")
}
fmt.Printf("%d\t%d\n", rec_cursor, play_cursor)
cursor_mu.Unlock()
}
}()
go func() {
for {
cursor_mu.Lock()
avail := rec_cursor - play_cursor
actual := avail
if avail < 0 {
avail = len(buf) - play_cursor
actual = avail
avail += rec_cursor
}
pc := play_cursor
cursor_mu.Unlock()
if avail <= delay_bytes {
fmt.Println("play: waiting")
time.Sleep(time.Millisecond * 100)
continue
}
frames_actual := actual / bytes_per_frame
fmt.Println("writing...")
err = play.Write(buf[pc:pc+actual], frames_actual)
if err != nil {
fmt.Println(err)
return
}
cursor_mu.Lock()
play_cursor += actual
if play_cursor == len(buf) {
play_cursor = 0
} else if play_cursor > len(buf) {
panic("wtf, play cursor overrun")
}
fmt.Printf("%d\t%d\n", rec_cursor, play_cursor)
cursor_mu.Unlock()
}
}()
select {}
}