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package main
import (
"encoding/json"
"fmt"
"log"
"os"
"github.com/cryptix/wav"
)
// Demux a 2 channel audio file and save the left channel as a mono file
// http://blog.bjornroche.com/2013/05/the-abcs-of-pcm-uncompressed-digital.html
func main() {
if len(os.Args) != 2 {
fmt.Fprintf(os.Stderr, "Usage: demux <file.wav>\n")
os.Exit(1)
}
testInfo, err := os.Stat(os.Args[1])
checkErr(err)
testWav, err := os.Open(os.Args[1])
checkErr(err)
wavReader, err := wav.NewReader(testWav, testInfo.Size())
checkErr(err)
fileMeta := wavReader.GetFile()
fmt.Println(dump(fileMeta))
if fileMeta.Channels != 2 {
log.Fatal("Please use a 2-channel audio file")
}
// A slice of many 1-4 byte samples
var left [][]byte
left = make([][]byte, fileMeta.NumberOfSamples/2)
var i uint32
var buf []byte
for i = 0; i < fileMeta.NumberOfSamples/2; i++ {
buf, err = wavReader.ReadRawSample()
checkErr(err)
left[i] = buf
// Throw the right-channel away
_, err = wavReader.ReadRawSample()
checkErr(err)
}
filename := "mono-" + testInfo.Name()
os.Remove(filename)
f, err := os.Create(filename)
checkErr(err)
// Create the headers for our new mono file
meta := wav.File{
Channels: 1,
SampleRate: fileMeta.SampleRate,
SignificantBits: fileMeta.SignificantBits,
}
writer, err := meta.NewWriter(f)
checkErr(err)
// Write to file
for _, sample := range left {
err = writer.WriteSample(sample)
checkErr(err)
}
err = writer.Close()
checkErr(err)
fmt.Println("Created Mono File", f.Name())
f, err = os.Open(f.Name())
checkErr(err)
stat, err := f.Stat()
checkErr(err)
wavReader, err = wav.NewReader(f, stat.Size())
checkErr(err)
fileMeta = wavReader.GetFile()
fmt.Println(dump(fileMeta))
}
func checkErr(err error) {
if err != nil {
panic(err)
}
}
func dump(v interface{}) string {
b, _ := json.MarshalIndent(v, "", " ")
return string(b)
}
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