func fadeout(s []audio.Sample, samples int) {
for i := range s {
if r := len(s) - i; r < samples {
s[i] *= audio.Sample(r) / audio.Sample(samples)
}
}
}
// readWav reads the wav file at the given path and returns it as a set
// of audio samples.
// TODO be much less picky about what kinds
// of file we accept.
func readWav(path string) ([]audio.Sample, error) {
f, err := os.Open(path)
if err != nil {
return nil, fmt.Errorf("cannot open file: %v", err)
}
defer f.Close()
r, err := wav.NewReader(f)
if err != nil {
return nil, fmt.Errorf("cannot make reader: %v", err)
}
h := r.Header().Format
if h.NumChannels != 1 {
return nil, fmt.Errorf("want 1 channel, got %d", h.NumChannels)
}
if h.SampleRate != drummachine.SampleRate {
return nil, fmt.Errorf("want sample rate %d, got %d", drummachine.SampleRate, h.SampleRate)
}
samples := make([]wav.Sample, r.Remaining())
n, err := r.Read(samples)
if n != len(samples) && err != nil {
return nil, fmt.Errorf("cannot read samples (%d): %v", n, err)
}
if n != len(samples) {
return nil, fmt.Errorf("only read %d/%d samples", n, len(samples))
}
auSamples := make([]audio.Sample, len(samples))
for i, s := range samples {
auSamples[i] = audio.Sample(s)
}
return auSamples, nil
}
func normalize(s []audio.Sample) {
max := audio.Sample(0)
for _, v := range s {
if v < 0 {
v *= -1
}
if v > max {
max = v
}
}
if max > 0 {
fac := 0.99 / max
for i := range s {
s[i] *= fac
}
}
}
func (m *Gate) Process(s []audio.Sample) {
p := audio.Sample(atomic.LoadInt64(&midiGate))
for i := range s {
s[i] = p
}
}
func (m *Note) Process(s []audio.Sample) {
p := (audio.Sample(atomic.LoadInt64(&midiNote)) - 69) / 120
for i := range s {
s[i] = p
}
}