mirror of
https://github.com/vsariola/sointu.git
synced 2025-05-28 03:10:24 -04:00
112 lines
3.7 KiB
Go
112 lines
3.7 KiB
Go
package sointu
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"math"
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)
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// Wav converts a stereo signal of 32-bit floats (L R L R..., length should be
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// divisible by 2) into a valid WAV-file, returned as a []byte array.
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//
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// If pcm16 is set to true, the samples in the WAV-file will be 16-bit signed
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// integers; otherwise the samples will be 32-bit floats
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func Wav(buffer []float32, pcm16 bool) ([]byte, error) {
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buf := new(bytes.Buffer)
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wavHeader(len(buffer), pcm16, buf)
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err := rawToBuffer(buffer, pcm16, buf)
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if err != nil {
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return nil, fmt.Errorf("Wav failed: %v", err)
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}
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return buf.Bytes(), nil
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}
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// Raw converts a stereo signal of 32-bit floats (L R L R..., length should be
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// divisible by 2) into a raw audio file, returned as a []byte array.
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//
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// If pcm16 is set to true, the samples will be 16-bit signed integers;
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// otherwise the samples will be 32-bit floats
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func Raw(buffer []float32, pcm16 bool) ([]byte, error) {
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buf := new(bytes.Buffer)
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err := rawToBuffer(buffer, pcm16, buf)
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if err != nil {
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return nil, fmt.Errorf("Raw failed: %v", err)
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}
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return buf.Bytes(), nil
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}
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func rawToBuffer(data []float32, pcm16 bool, buf *bytes.Buffer) error {
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var err error
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if pcm16 {
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int16data := make([]int16, len(data))
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for i, v := range data {
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int16data[i] = int16(clamp(int(v*math.MaxInt16), math.MinInt16, math.MaxInt16))
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}
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err = binary.Write(buf, binary.LittleEndian, int16data)
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} else {
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err = binary.Write(buf, binary.LittleEndian, data)
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}
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if err != nil {
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return fmt.Errorf("could not binary write data to binary buffer: %v", err)
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}
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return nil
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}
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// wavHeader writes a wave header for either float32 or int16 .wav file into the
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// bytes.buffer. It needs to know the length of the buffer and assumes stereo
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// sound, so the length in stereo samples (L + R) is bufferlength / 2. If pcm16
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// = true, then the header is for int16 audio; pcm16 = false means the header is
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// for float32 audio. Assumes 44100 Hz sample rate.
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func wavHeader(bufferLength int, pcm16 bool, buf *bytes.Buffer) {
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// Refer to: http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html
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numChannels := 2
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sampleRate := 44100
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var bytesPerSample, chunkSize, fmtChunkSize, waveFormat int
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var factChunk bool
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if pcm16 {
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bytesPerSample = 2
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chunkSize = 36 + bytesPerSample*bufferLength
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fmtChunkSize = 16
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waveFormat = 1 // PCM
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factChunk = false
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} else {
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bytesPerSample = 4
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chunkSize = 50 + bytesPerSample*bufferLength
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fmtChunkSize = 18
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waveFormat = 3 // IEEE float
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factChunk = true
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}
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buf.Write([]byte("RIFF"))
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binary.Write(buf, binary.LittleEndian, uint32(chunkSize))
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buf.Write([]byte("WAVE"))
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buf.Write([]byte("fmt "))
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binary.Write(buf, binary.LittleEndian, uint32(fmtChunkSize))
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binary.Write(buf, binary.LittleEndian, uint16(waveFormat))
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binary.Write(buf, binary.LittleEndian, uint16(numChannels))
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binary.Write(buf, binary.LittleEndian, uint32(sampleRate))
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binary.Write(buf, binary.LittleEndian, uint32(sampleRate*numChannels*bytesPerSample)) // avgBytesPerSec
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binary.Write(buf, binary.LittleEndian, uint16(numChannels*bytesPerSample)) // blockAlign
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binary.Write(buf, binary.LittleEndian, uint16(8*bytesPerSample)) // bits per sample
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if fmtChunkSize > 16 {
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binary.Write(buf, binary.LittleEndian, uint16(0)) // size of extension
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}
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if factChunk {
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buf.Write([]byte("fact"))
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binary.Write(buf, binary.LittleEndian, uint32(4)) // fact chunk size
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binary.Write(buf, binary.LittleEndian, uint32(bufferLength)) // sample length
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}
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buf.Write([]byte("data"))
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binary.Write(buf, binary.LittleEndian, uint32(bytesPerSample*bufferLength))
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}
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func clamp(value, min, max int) int {
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if value < min {
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return min
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}
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if value > max {
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return max
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}
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return value
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}
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