1, Operation steps:
1. Set recording related parameters, audio acquisition source, sampling rate, channel and data format
companion object{
private const val TAG:String = "OnlyAudioRecorder"
private const val AudioSource = MediaRecorder.AudioSource.MIC//Student source
private const val SampleRate = 16000//sampling rate
private const val Channel = AudioFormat.CHANNEL_IN_MONO//Mono channel
private const val EncodingType = AudioFormat.ENCODING_PCM_16BIT//data format
private val PCMPath = Environment.getExternalStorageDirectory().path.toString()+"/zzz/RawAudio.pcm"
private val WAVPath = Environment.getExternalStorageDirectory().path.toString()+"/zzz/FinalAudio.wav"
//Single example of double check
val instance:OnlyAudioRecorder by lazy (mode = LazyThreadSafetyMode.SYNCHRONIZED){
OnlyAudioRecorder()
}
}2. Calculate the minimum recording buffer size
bufferSizeInByte = AudioRecord.getMinBufferSize(SampleRate, Channel, EncodingType)
3. Create audioRecord object
audioRecorder = AudioRecord(AudioSource, SampleRate, Channel,
EncodingType, bufferSizeInByte)4. Start recording
audioRecorder?.startRecording()
5. Save the recording file
while (isRecord && audioRecorder!=null) {
length = audioRecorder!!.read(audioData, 0, bufferSizeInByte)//Get audio data
if (AudioRecord.ERROR_INVALID_OPERATION != length) {
out.write(audioData, 0, length)//write file
out.flush()
}
}6. Close recording and release related resources after recording
fun stopRecord() {
audioRecorder?.stop()
audioRecorder?.release()
isRecord = false
audioRecorder = null
}7. It's easy to convert pcm file to WAV file. You only need to add a header in front of pcm. The last part of the complete code is.
2, Precautions:
Pay attention to the permission of recording, reading and writing local files. Remember to request the permission dynamically above 23.
<uses-permission android:name="android.permission.RECORD_AUDIO"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>3, Full source:
import android.media.AudioFormat
import android.media.AudioRecord
import android.media.MediaRecorder
import android.os.Environment
import java.io.BufferedOutputStream
import java.io.File
import java.io.FileInputStream
import java.io.FileOutputStream
/**
*@author :
*@date : 2020/1/17
*@description :Audio only class
*/
class OnlyAudioRecorder private constructor(){
//1. Set recording related parameters, audio acquisition source, sampling rate, channel and data format
//2. Calculate the minimum recording buffer size
//3. Create audioRecord object
//4. Start recording
//5. Create files to save PCM files
//6. Close recording and release related resources after recording
//7. Convert pcm file to WAV file
companion object{
private const val TAG:String = "OnlyAudioRecorder"
private const val AudioSource = MediaRecorder.AudioSource.MIC//Student source
private const val SampleRate = 16000//sampling rate
private const val Channel = AudioFormat.CHANNEL_IN_MONO//Mono channel
private const val EncodingType = AudioFormat.ENCODING_PCM_16BIT//data format
private val PCMPath = Environment.getExternalStorageDirectory().path.toString()+"/zzz/RawAudio.pcm"
private val WAVPath = Environment.getExternalStorageDirectory().path.toString()+"/zzz/FinalAudio.wav"
//Single example of double check
val instance:OnlyAudioRecorder by lazy (mode = LazyThreadSafetyMode.SYNCHRONIZED){
OnlyAudioRecorder()
}
}
private var bufferSizeInByte:Int = 0//Minimum recording buffer
private var audioRecorder:AudioRecord? = null//Recording object
private var isRecord = false
private fun initRecorder() {//Initializing the audioRecord object
bufferSizeInByte = AudioRecord.getMinBufferSize(SampleRate, Channel, EncodingType)
audioRecorder = AudioRecord(AudioSource, SampleRate, Channel,
EncodingType, bufferSizeInByte)
}
fun startRecord():Int {
if (isRecord) {
return -1
} else{
audioRecorder?: initRecorder()
audioRecorder?.startRecording()
isRecord = true
AudioRecordToFile().start()
return 0
}
}
fun stopRecord() {
audioRecorder?.stop()
audioRecorder?.release()
isRecord = false
audioRecorder = null
}
private fun writeDateTOFile() {
var audioData = ByteArray(bufferSizeInByte)
val file = File(PCMPath)
if (!file.parentFile.exists()) {
file.parentFile.mkdirs()
}
if (file.exists()) {
file.delete()
}
file.createNewFile()
val out = BufferedOutputStream(FileOutputStream(file))
var length = 0
while (isRecord && audioRecorder!=null) {
length = audioRecorder!!.read(audioData, 0, bufferSizeInByte)//Get audio data
if (AudioRecord.ERROR_INVALID_OPERATION != length) {
out.write(audioData, 0, length)//write file
out.flush()
}
}
out.close()
}
//Converting pcm files to WAV files
private fun copyWaveFile(pcmPath: String, wavPath: String) {
var fileIn = FileInputStream(pcmPath)
var fileOut = FileOutputStream(wavPath)
val data = ByteArray(bufferSizeInByte)
val totalAudioLen = fileIn.channel.size()
val totalDataLen = totalAudioLen + 36
writeWaveFileHeader(fileOut, totalAudioLen, totalDataLen)
var count = fileIn.read(data, 0, bufferSizeInByte)
while (count != -1) {
fileOut.write(data, 0, count)
fileOut.flush()
count = fileIn.read(data, 0, bufferSizeInByte)
}
fileIn.close()
fileOut.close()
}
//Add file header in WAV format
private fun writeWaveFileHeader(out:FileOutputStream , totalAudioLen:Long,
totalDataLen:Long){
val channels = 1
val byteRate = 16 * SampleRate * channels / 8
val header = ByteArray(44)
header[0] = 'R'.toByte()
header[1] = 'I'.toByte()
header[2] = 'F'.toByte()
header[3] = 'F'.toByte()
header[4] = (totalDataLen and 0xff).toByte()
header[5] = (totalDataLen shr 8 and 0xff).toByte()
header[6] = (totalDataLen shr 16 and 0xff).toByte()
header[7] = (totalDataLen shr 24 and 0xff).toByte()
header[8] = 'W'.toByte()
header[9] = 'A'.toByte()
header[10] = 'V'.toByte()
header[11] = 'E'.toByte()
header[12] = 'f'.toByte() // 'fmt ' chunk
header[13] = 'm'.toByte()
header[14] = 't'.toByte()
header[15] = ' '.toByte()
header[16] = 16 // 4 bytes: size of 'fmt ' chunk
header[17] = 0
header[18] = 0
header[19] = 0
header[20] = 1 // format = 1
header[21] = 0
header[22] = channels.toByte()
header[23] = 0
header[24] = (SampleRate and 0xff).toByte()
header[25] = (SampleRate shr 8 and 0xff).toByte()
header[26] = (SampleRate shr 16 and 0xff).toByte()
header[27] = (SampleRate shr 24 and 0xff).toByte()
header[28] = (byteRate and 0xff).toByte()
header[29] = (byteRate shr 8 and 0xff).toByte()
header[30] = (byteRate shr 16 and 0xff).toByte()
header[31] = (byteRate shr 24 and 0xff).toByte()
header[32] = (2 * 16 / 8).toByte() // block align
header[33] = 0
header[34] = 16 // bits per sample
header[35] = 0
header[36] = 'd'.toByte()
header[37] = 'a'.toByte()
header[38] = 't'.toByte()
header[39] = 'a'.toByte()
header[40] = (totalAudioLen and 0xff).toByte()
header[41] = (totalAudioLen shr 8 and 0xff).toByte()
header[42] = (totalAudioLen shr 16 and 0xff).toByte()
header[43] = (totalAudioLen shr 24 and 0xff).toByte()
out.write(header, 0, 44)
}
private inner class AudioRecordToFile : Thread() {
override fun run() {
super.run()
writeDateTOFile()
copyWaveFile(PCMPath, WAVPath)
}
}
}Four, use method:
val audioRecord = OnlyAudioRecorder.instance audioRecord.startRecord()//Start recording audioRecord.stopRecord()//Stop recording
