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