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//
// rhimportd
//
// The Radio Helsinki Rivendell Import Daemon
//
//
// Copyright (C) 2015-2016 Christian Pointner <equinox@helsinki.at>
//
// This file is part of rhimportd.
//
// rhimportd is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// any later version.
//
// rhimportd is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with rhimportd. If not, see <http://www.gnu.org/licenses/>.
//
package rhimport
import (
"bytes"
"encoding/binary"
"errors"
"io"
"math"
"time"
)
const (
_RIFF_TAG = "RIFF"
_WAVE_TAG = "WAVE"
_FMT_TAG = "fmt "
_FMT_ID_PCM = 0x0001
_DATA_TAG = "data"
)
type wavHeader struct {
riffTag [4]uint8
riffLength uint32
waveTag [4]uint8
fmtTag [4]uint8
fmtLength uint32
fmtID uint16
nChannels uint16
sampleRate uint32
byteRate uint32
blockAlign uint16
sampleDepth uint16
dataTag [4]uint8
dataLength uint32
}
func (h *wavHeader) Bytes() []byte {
buf := &bytes.Buffer{}
binary.Write(buf, binary.LittleEndian, h)
return buf.Bytes()
}
type sampleGenerator interface {
Reset(samplePeriod float64)
GetSamples(nSamples uint32, channels uint16) []float64 // this needs to be normalized, aka -1 <= value <= 1
}
type wavFile struct {
header wavHeader
headerSize uint32
pcmSampleMax float64
pcmSampleBytes uint32
samplePeriod float64
generator sampleGenerator
readOffset uint32
}
func (wav *wavFile) GetFileSize() (size uint32) {
return wav.headerSize + wav.header.dataLength
}
func (wav *wavFile) Read(p []byte) (n int, err error) {
n = 0
if wav.readOffset >= (wav.header.riffLength + 8) {
return n, io.EOF
}
if wav.readOffset < wav.headerSize {
n = copy(p, wav.header.Bytes()[wav.readOffset:])
wav.readOffset += uint32(n)
wav.generator.Reset(wav.samplePeriod)
}
if n >= len(p) {
return
}
nsamples := uint32(len(p)-n) / uint32(wav.header.blockAlign)
data := wav.generator.GetSamples(nsamples, wav.header.nChannels)
switch wav.header.fmtID {
case _FMT_ID_PCM:
idx := 0
for _, normalized := range data {
scaled := wav.pcmSampleMax * normalized
sample := uint64(math.Trunc(math.Min(scaled, wav.pcmSampleMax)))
var b [8]byte
binary.LittleEndian.PutUint64(b[:], sample)
copy(p[n:n+int(wav.pcmSampleBytes)], b[:])
n += int(wav.pcmSampleBytes)
wav.readOffset += wav.pcmSampleBytes
if wav.readOffset >= (wav.header.riffLength + 8) {
return n, io.EOF
}
idx++
}
default:
return n, errors.New("unknown sample format ID")
}
return
}
func newPCMWavFile(sampleRate uint32, sampleDepth uint16, channels uint16, length time.Duration) (wav *wavFile, err error) {
wav = &wavFile{}
wav.headerSize = 8 + 4 + 8 + 16 + 8
if length <= 0 {
return nil, errors.New("invalid length: must be > 0")
}
wav.pcmSampleMax = float64(uint64(1<<(sampleDepth-1)) - 1)
wav.pcmSampleBytes = ((uint32(sampleDepth) + 7) / 8)
wav.samplePeriod = 1.0 / float64(sampleRate)
frameSize32 := uint32(channels) * wav.pcmSampleBytes
if frameSize32 > math.MaxUint16 {
return nil, errors.New("frame size exceeds 16bit values (64kB)")
}
frameSize := uint16(frameSize32)
period_ns := float64(time.Second) / float64(sampleRate)
nFramesF64 := (float64(length) / period_ns)
if nFramesF64 < 1 {
nFramesF64 = 1
}
if nFramesF64 > math.MaxUint32 {
return nil, errors.New("number of frames exceeds limit (reduce length and/or sample-rate)")
}
nFrames := uint32(nFramesF64)
if nFrames > ((math.MaxUint32 - wav.headerSize) / uint32(frameSize)) {
return nil, errors.New("file length exceeds 32bit values (4GB)")
}
dataLen := nFrames * uint32(frameSize)
copy(wav.header.riffTag[:], _RIFF_TAG)
wav.header.riffLength = wav.headerSize - 8 + dataLen
copy(wav.header.waveTag[:], _WAVE_TAG)
copy(wav.header.fmtTag[:], _FMT_TAG)
wav.header.fmtLength = 16
wav.header.fmtID = _FMT_ID_PCM
wav.header.nChannels = channels
wav.header.sampleRate = sampleRate
wav.header.byteRate = sampleRate * uint32(frameSize)
wav.header.blockAlign = frameSize
wav.header.sampleDepth = sampleDepth
copy(wav.header.dataTag[:], _DATA_TAG)
wav.header.dataLength = dataLen
return
}
type silenceGenerator struct {
}
func newSilenceGenerator() *silenceGenerator {
return &silenceGenerator{}
}
func (s *silenceGenerator) Reset(samplePeriod float64) {
// nothing here
}
func (s *silenceGenerator) GetSamples(nSamples uint32, nChannels uint16) (data []float64) {
data = make([]float64, int(nSamples)*int(nChannels))
return
}
type sinusGenerator struct {
amp float64
freq float64
sp float64
t float64
}
func newSinusGenerator(ampDB, freq float64) (sin *sinusGenerator) {
sin = &sinusGenerator{}
sin.amp = math.Pow(10.0, (ampDB / 20.0))
sin.freq = freq
return
}
func (sin *sinusGenerator) Reset(samplePeriod float64) {
sin.sp = samplePeriod
sin.t = 0
}
func (sin *sinusGenerator) GetSamples(nSamples uint32, nChannels uint16) (data []float64) {
data = make([]float64, int(nSamples)*int(nChannels))
for i := 0; i < int(nSamples); i++ {
val := sin.amp * math.Sin(2*math.Pi*sin.freq*sin.t)
for j := 0; j < int(nChannels); j++ {
data[i*int(nChannels)+j] = val
}
sin.t += sin.sp
}
return
}
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