Android音视频开发-AudioRecord

Android音视频开发-AudioRecord

本篇文章主要讲下AudioRecord.

1: 简介

AudioRecord是Android平台上的一个类，用于实时录制音频数据。它提供了一种方便的方式来捕获和处理音频流。

以下是关于AudioRecord的一些介绍：

1. 音频源：Record可以从多种音频源中录制音频数据例如麦克风、电话线路、语音识别等。
2. 音频格式：可以选择不同的音频格式来录制音频数据，如PCM（脉冲编码调制）、AAC（级音频编码）等。
3. 缓冲区AudioRecord使用一个缓冲区来存储录制的音频数据。开发者可以指定缓冲区的大小，以适应不同的录制需求。
4. 录制状态：通过调用start()方法开始录制音频数据，并可以通过stop()方法停止录制。还可以使用getState()方法获取当前的录制状态。
5. 回调函数：可以注册一个回调函数，当有新的音频数据可用时，系统会自动调用回调函数进行处理。
6. 音频参数：可以设置采样率、声道数和位深度等参数，以满足不同的录制需求。
7. 权限要求：需要在AndroidManifest.xml文件中添加相应的权限声明android.permission.RECORD_AUDIO权限。

2: AudioRecord对象

首先看下AudioRecord的构造函数:

public AudioRecord(int audioSource, int sampleRateInHz, int channelConfig, int audioFormat,
        int bufferSizeInBytes)
throws IllegalArgumentException {
    this((new AudioAttributes.Builder())
                .setInternalCapturePreset(audioSource)
                .build(),
            (new AudioFormat.Builder())
                .setChannelMask(getChannelMaskFromLegacyConfig(channelConfig,
                                    true/*allow legacy configurations*/))
                .setEncoding(audioFormat)
                .setSampleRate(sampleRateInHz)
                .build(),
            bufferSizeInBytes,
            AudioManager.AUDIO_SESSION_ID_GENERATE);
}

参数如下:

1. audioSource:录制源,具体的参数为MediaRecorder.AudioSource.
2. sampleRateInHz:采样率,单位赫兹.44100Hz是目前唯一保证在所有设备上工作的速率.
3. channelConfig:音频通道的配置.
4. audioFormat:音频数据的格式
5. bufferSizeInBytes:缓冲区大小.

创建AudioRecord对象:

int audioSource = MediaRecorder.AudioSource.MIC; // 设置音频源为麦克风
int sampleRateInHz = 44100; // 设置采样率为44100Hz
int channelConfig = AudioFormat.CHANNEL_IN_MONO; // 设置通道配置为单声道
int audioFormat = AudioFormat.ENCODING_PCM_16BIT; // 设置音频格式为16位PCM
int bufferSizeInBytes = AudioRecord.getMinBufferSize(sampleRateInHz, channelConfig, audioFormat); // 获取缓冲区大小
audioRecord = new AudioRecord(audioSource, sampleRateInHz, channelConfig, audioFormat, bufferSizeInBytes);

3: 开启录制

开启录制很简单,调用audioRecord的startRecording()方法即可.

audioRecord.startRecording();

另外为了写入文件,我们这里设置个录制状态:

isRecording = true;

创建缓冲区,存储录音文件.

byte[] buffer = new byte[bufferSizeInBytes];

循环读取,写入文件:

new Thread(() -> writeAudioPcm()).start();

writeAudioPcm()详细代码如下:

private void writeAudioPcm() {
    byte[] bytes = new byte[bufferSizeInBytes];
    FileOutputStream fos = null;
    try {
        File file = new File("sdcard/audioRecord.pcm");
        if (!file.exists()) {
            file.createNewFile();
        }
        fos = new FileOutputStream(file);
        while (isRecording) {
            int read = audioRecord.read(bytes, 0, bytes.length);
            if (read > 0) {
                fos.write(read);
            }
        }
    } catch (Throwable e) {
        Log.e(TAG, "writeAudioPcm: ", e);
    } finally {
        try {
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

4: 结束录制

按需停止录制音频并释放资源.

private void stopAudio() {
    isRecording = false;
    if (audioRecord != null) {
        audioRecord.stop();
        audioRecord.release();
    }
    pcmToWav();
}

5: pcm转Wav.

最后就是将pcm转为WAV格式.

首先我们先根据音频的采样率,声道等参数,获取wav的header信息.

/**
 * 头部信息共44字节
 * @param sampleRate
 * @param channels
 * @param bitDepth
 * @param dataSize
 * @return
 * @throws IOException
 */
    public byte[] getWavHeader(int sampleRate, int channels, int bitDepth, long dataSize) {
        byte[] header = new byte[44];
        // ChunkID，RIFF标识
        header[0] = 'R';
        header[1] = 'I';
        header[2] = 'F';
        header[3] = 'F';

        // ChunkSize，文件长度
        long totalSize = dataSize + 36;
        header[4] = (byte) (totalSize & 0xff);
        header[5] = (byte) ((totalSize >> 8) & 0xff);
        header[6] = (byte) ((totalSize >> 16) & 0xff);
        header[7] = (byte) ((totalSize >> 24) & 0xff);

        // Format，WAVE标识
        header[8] = 'W';
        header[9] = 'A';
        header[10] = 'V';
        header[11] = 'E';

        // Subchunk1ID，fmt标识
        header[12] = 'f';
        header[13] = 'm';
        header[14] = 't';
        header[15] = ' ';

        // Subchunk1Size，格式信息长度
        header[16] = 16;
        header[17] = 0;
        header[18] = 0;
        header[19] = 0;

        // AudioFormat，音频格式（PCM为1）
        header[20] = 1;
        header[21] = 0;

        // NumChannels，声道数
        header[22] = (byte) channels;
        header[23] = 0;

        // SampleRate，采样率
        header[24] = (byte) (sampleRate & 0xff);
        header[25] = (byte) ((sampleRate >> 8) & 0xff);
        header[26] = (byte) ((sampleRate >> 16) & 0xff);
        header[27] = (byte) ((sampleRate >> 24) & 0xff);

        // ByteRate，比特率
        int byteRate = sampleRate * channels * bitDepth / 8;
        header[28] = (byte) (byteRate & 0xff);
        header[29] = (byte) ((byteRate >> 8) & 0xff);
        header[30] = (byte) ((byteRate >> 16) & 0xff);
        header[31] = (byte) ((byteRate >> 24) & 0xff);

        // BlockAlign，块对齐
        int blockAlign = channels * bitDepth / 8;
        header[32] = (byte) blockAlign;
        header[33] = 0;

        // BitsPerSample，采样位深度
        header[34] = (byte) bitDepth;
        header[35] = 0;

        // Subchunk2ID，data标识
        header[36] = 'd';
        header[37] = 'a';
        header[38] = 't';
        header[39] = 'a';

        // Subchunk2Size，音频数据长度 dataHdrLength
        header[40] = (byte) (dataSize & 0xff);
        header[41] = (byte) ((dataSize >> 8) & 0xff);
        header[42] = (byte) ((dataSize >> 16) & 0xff);
        header[43] = (byte) ((dataSize >> 24) & 0xff);
        return header;
    }

转换方法如下:

private void pcmToWav() {
    File pcmFile = new File("sdcard/audioRecord.pcm");
    File wavFile = new File("sdcard/audioRecord.wav");
    // 创建WAV文件头
    short i = (short) (channelConfig == AudioFormat.CHANNEL_IN_MONO ? 1 : 2);
    byte[] header = getWavHeader(sampleRateInHz,i,16,pcmFile.length());
    // 写入WAV文件头
    FileOutputStream wavOutputStream = null;
    try {
        wavOutputStream = new FileOutputStream(wavFile);
        wavOutputStream.write(header);
        // 写入PCM数据
        FileInputStream pcmInputStream = new FileInputStream(pcmFile);
        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = pcmInputStream.read(buffer)) != -1) {
            wavOutputStream.write(buffer, 0, bytesRead);
        }
        // 关闭文件流
        pcmInputStream.close();
        wavOutputStream.close();
    } catch (Throwable e) {
        Log.e(TAG, "pcmToWav: ", e);
    }

}

6:机型适配.

在华为mate50上测试时,授予权限开启录音后崩溃:

2024-04-09 12:00:09.763 1438-1438/? E/ServiceUtilities: Request requires android.permission.MODIFY_AUDIO_SETTINGS
2024-04-09 12:00:09.767 1438-1438/? E/AudioPolicyIntefaceImpl: getInputForAttr permission denied: recording not allowed for AttributionSourceState{pid: 11582, uid: 10157, packageName: com.test.media, attributionTag: (null), token: , renouncedPermissions: [], next: [], uidPidOrigin: -1}
2024-04-09 12:00:09.767 1438-1438/? E/AudioFlinger: createRecord() getInputForAttr return error -1
2024-04-09 12:00:09.767 11582-11582/com.test.media E/AudioRecord: createRecord_l(-1): AudioFlinger could not create record track, status: -1
2024-04-09 12:00:09.767 11582-11582/com.test.media E/AudioRecord-JNI: Error creating AudioRecord instance: initialization check failed with status -1.
2024-04-09 12:00:09.768 11582-11582/com.test.media E/android.media.AudioRecord: Error code -20 when initializing native AudioRecord object.
2024-04-09 12:00:09.770 11582-11582/com.test.media E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.test.media, PID: 11582
    java.lang.IllegalStateException: startRecording() called on an uninitialized AudioRecord.
        at android.media.AudioRecord.startRecording(AudioRecord.java:1326)
        at com.test.media.AudioRecordActivity.startAudio(AudioRecordActivity.java:98)
        at com.test.media.AudioRecordActivity.onClick(AudioRecordActivity.java:41)
        at android.view.View.performClick(View.java:7682)
        at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:967)
        at android.view.View.performClickInternal(View.java:7651)
        at android.view.View.access$3700(View.java:886)
        at android.view.View$PerformClick.run(View.java:30173)
        at android.os.Handler.handleCallback(Handler.java:966)
        at android.os.Handler.dispatchMessage(Handler.java:110)
        at android.os.Looper.loopOnce(Looper.java:205)
        at android.os.Looper.loop(Looper.java:293)
        at android.app.ActivityThread.loopProcess(ActivityThread.java:9934)
        at android.app.ActivityThread.main(ActivityThread.java:9923)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:586)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1240)

1. 根据日志输出,授予:android.permission.MODIFY_AUDIO_SETTINGS权限.增加权限无效,经过测试无效.

2. Error code -20 when initializing native AudioRecord object.

   错误码-20:AUDIORECORD_ERROR_SETUP_NATIVEINITFAILED.

   怀疑是配置有问题,尝试切换声道,采样率等,仍然无效.

3. AudioPolicyIntefaceImpl: getInputForAttr permission denied: recording not allowed for AttributionSourceState{pid: 11582, uid: 10157, packageName: com.test.media, attributionTag: (null), token: , renouncedPermissions: [], next: [], uidPidOrigin: -1}

   最后发现还是权限问题,由于我未动态申请权限,是通过应用程序直接授予的麦克风权限.

   添加动态申请权限代码:

   if (ContextCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
       ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.RECORD_AUDIO}, 1101);
   }
   

   问题解决.