Android 无法以 32 位 wav PCM 录制

Question

我一直在尝试使用 32 位深度的 AudioRecord 在 android 上录制人声并将它们写入 wav 文件。我知道使用 AudioFormat.ENCODING_PCM_FLOAT，只有 API 级别 23 或更高级别（如文档所述）才能使用 32 位精度进行录制。我在 API 级别 23 的设备上做了一些测试，但仍然出于某种原因，生成的音频已损坏（我只能听到完全的噪音）。这是我的代码的样子：

private AudioRecord mRecorder;
private int mBufferSize;

private Thread mRecordingThread;
private boolean mIsRecording;

private String tempPath = "/some/path/tempFile.wav";
private String outputPath = "/some/path/recording.wav";

@TargetApi(23)
public void startRecording() {
    mBufferSize = AudioRecord.getMinBufferSize(16000, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_FLOAT);
    mRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC, 16000, AudioFormat.CHANNEL_IN_MONO,
            AudioFormat.ENCODING_PCM_FLOAT, mBufferSize);

    if (mRecorder.getState() == AudioRecord.STATE_INITIALIZED
            && mBufferSize != AudioRecord.ERROR_BAD_VALUE) {
        return;
    }

    mRecordingThread = new Thread(new Runnable() {
        @Override
        public void run() {
            android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_AUDIO);
            try {
                FileOutputStream outputStream = new FileOutputStream(tempPath);
                float[] audioData = new float[mBufferSize / 4];

                mRecorder.startRecording();
                mIsRecording = true;

                while (mIsRecording) {
                    int readSize = mRecorder.read(audioData, 0, audioData.length, AudioRecord.READ_BLOCKING);
                    if (readSize == AudioRecord.ERROR_INVALID_OPERATION || readSize == AudioRecord.ERROR_BAD_VALUE) {
                        break;
                    }

                    // convert float to byte
                    byte[] bytes = new byte[audioData.length * 4];
                    ByteBuffer.wrap(bytes).order(ByteOrder.nativeOrder()).asFloatBuffer().put(audioData);
                    try {
                        outputStream.write(bytes);
                    } catch (IOException e) {
                        Log.e("Recorder", e.getMessage(), e);
                    }
                }
                outputStream.close();

            } catch (IOException e) {
                Log.e("Recorder", e.getMessage(), e);
            } catch (Exception e) {
                Log.e("Recorder", e.getMessage(), e);
            }
        }
    });
    mRecordingThread.start();
}


public void stopRecording() {
    if (mIsRecording) {
        mIsRecording = false;
        if (mRecordingThread != null && mRecordingThread.getState() != Thread.State.NEW
                && mRecordingThread.getState() != Thread.State.TERMINATED) {
            try {
                mRecordingThread.join();
            } catch (InterruptedException e) {
                // ...
            }
        }
        if (mRecorder.getState() == AudioRecord.RECORDSTATE_RECORDING) {
            mRecorder.stop();
        }
        mRecordingThread = null;
        generateFinalAudio();
    }
}

public void generateFinalAudio() {
    CopyAudioTask task = new CopyAudioTask();
    task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, tempPath, outputPath);
}

private class CopyAudioTask extends AsyncTask<String, String, Void> {
    @Override
    protected Void doInBackground(String... params) {
        String tmpPath = params[0];
        String outPath = params[1];

        try {
            FileInputStream in = new FileInputStream(tmpPath);
            FileOutputStream out = new FileOutputStream(outPath);
            byte[] data = new byte[mBufferSize];

            writeWaveFileHeader(in, out);
            while (in.read(data) != -1) {
                out.write(data);
            }
            in.close();
            out.close();

        } catch (Exception e) {
            Log.e("Recorder", e.getMessage(), e);
        }
        return null;
    }
}

private void writeWaveFileHeader(FileInputStream in, FileOutputStream out) throws IOException {
    int bitWidth = 32;
    long longSampleRate = mRecorder.getSampleRate();
    int channels = mRecorder.getChannelCount();
    long totalAudioLen = in.getChannel().size();
    long totalDataLen = totalAudioLen + 36;
    long byteRate = bitWidth * longSampleRate * channels / 8;

    byte[] header = new byte[44];

    header[0] = 'R'; // RIFF/WAVE header
    header[1] = 'I';
    header[2] = 'F';
    header[3] = 'F';
    header[4] = (byte) (totalDataLen & 0xff);
    header[5] = (byte) ((totalDataLen >> 8) & 0xff);
    header[6] = (byte) ((totalDataLen >> 16) & 0xff);
    header[7] = (byte) ((totalDataLen >> 24) & 0xff);
    header[8] = 'W';
    header[9] = 'A';
    header[10] = 'V';
    header[11] = 'E';
    header[12] = 'f'; // 'fmt ' chunk
    header[13] = 'm';
    header[14] = 't';
    header[15] = ' ';
    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] = (byte) channels;
    header[23] = 0;
    header[24] = (byte) (longSampleRate & 0xff);
    header[25] = (byte) ((longSampleRate >> 8) & 0xff);
    header[26] = (byte) ((longSampleRate >> 16) & 0xff);
    header[27] = (byte) ((longSampleRate >> 24) & 0xff);
    header[28] = (byte) (byteRate & 0xff);
    header[29] = (byte) ((byteRate >> 8) & 0xff);
    header[30] = (byte) ((byteRate >> 16) & 0xff);
    header[31] = (byte) ((byteRate >> 24) & 0xff);
    header[32] = (byte) (channels * bitWidth / 8); // block align
    header[33] = 0;
    header[34] = (byte) bitWidth; // bits per sample
    header[35] = 0;
    header[36] = 'd';
    header[37] = 'a';
    header[38] = 't';
    header[39] = 'a';
    header[40] = (byte) (totalAudioLen & 0xff);
    header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
    header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
    header[43] = (byte) ((totalAudioLen >> 24) & 0xff);

    out.write(header, 0, 44);
}

任何人都可以找出我在这里做错了什么吗？我试过使用 16 位（ENCODING_PCM_16BIT，并使用 short[] 作为数据缓冲区）并且它运行良好。

任何帮助将不胜感激。谢谢！

Answer 1

好的，我现在明白了。问题出在 header 上。对于 32 位浮点 PCM 数据，header[20] 的值应为 3 或 0x0003 page.

Answer 2

对于将问题中的代码用作模板（即 Ctrl+C Ctrl+V）的其他任何人，请不要忘记在此处的第一行中将 == 更改为 !=。好像是复制粘贴错误之类的。无论如何，更改此行后它将开始工作。

if (mRecorder.getState() == AudioRecord.STATE_INITIALIZED
        && mBufferSize != AudioRecord.ERROR_BAD_VALUE) {
    return;
}

Android 无法以 32 位 wav PCM 录制

Android Recording in 32-bit wav PCM not working

android

audio

wav

audiorecord

android-audiorecord