58 lines
1.1 KiB
Go
58 lines
1.1 KiB
Go
package main
|
|
|
|
// typedef unsigned char Uint8;
|
|
// void SineWave(void *userdata, Uint8 *stream, int len);
|
|
import "C"
|
|
import (
|
|
"log"
|
|
"math"
|
|
"reflect"
|
|
"unsafe"
|
|
|
|
"github.com/veandco/go-sdl2/sdl"
|
|
)
|
|
|
|
const (
|
|
toneHz = 440
|
|
sampleHz = 48000
|
|
dPhase = 2 * math.Pi * toneHz / sampleHz
|
|
)
|
|
|
|
//export SineWave
|
|
func SineWave(userdata unsafe.Pointer, stream *C.Uint8, length C.int) {
|
|
n := int(length)
|
|
hdr := reflect.SliceHeader{Data: uintptr(unsafe.Pointer(stream)), Len: n, Cap: n}
|
|
buf := *(*[]C.Uint8)(unsafe.Pointer(&hdr))
|
|
|
|
var phase float64
|
|
for i := 0; i < n; i += 2 {
|
|
phase += dPhase
|
|
sample := C.Uint8((math.Sin(phase) + 0.999999) * 128)
|
|
buf[i] = sample
|
|
buf[i+1] = sample
|
|
}
|
|
}
|
|
|
|
func main() {
|
|
if err := sdl.Init(sdl.INIT_AUDIO); err != nil {
|
|
log.Println(err)
|
|
return
|
|
}
|
|
defer sdl.Quit()
|
|
|
|
spec := &sdl.AudioSpec{
|
|
Freq: sampleHz,
|
|
Format: sdl.AUDIO_U8,
|
|
Channels: 2,
|
|
Samples: sampleHz,
|
|
Callback: sdl.AudioCallback(C.SineWave),
|
|
}
|
|
if err := sdl.OpenAudio(spec, nil); err != nil {
|
|
log.Println(err)
|
|
return
|
|
}
|
|
sdl.PauseAudio(false)
|
|
sdl.Delay(5000) // play audio for long enough to understand whether it works
|
|
sdl.CloseAudio()
|
|
}
|