Android MediaCodec 录制音频功能完整代码

以下是一个简单的 Android MediaCodec 录制音频的完整代码示例：

import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaFormat;
import android.media.MediaMuxer;
import android.os.Build;
import android.os.Environment;
import android.util.Log;

import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;

public class AudioRecorder {

    private static final String TAG = "AudioRecorder";

    private static final String AUDIO_MIME_TYPE = "audio/mp4a-latm";
    private static final int AUDIO_SAMPLE_RATE = 44100; // 44.1kHz
    private static final int AUDIO_CHANNEL_COUNT = 1; // mono
    private static final int AUDIO_BIT_RATE = 64000;

    private static final int BUFFER_SIZE = 2 * AudioRecord.getMinBufferSize(AUDIO_SAMPLE_RATE,
            AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);

    private MediaCodec mEncoder;
    private MediaMuxer mMuxer;
    private int mTrackIndex = -1;
    private boolean mMuxerStarted = false;
    private long mStartTime = 0;

    public void startRecording() throws IOException {
        File outputFile = new File(Environment.getExternalStorageDirectory(),
                "audio_record.mp4");

        mEncoder = MediaCodec.createEncoderByType(AUDIO_MIME_TYPE);
        MediaFormat format = new MediaFormat();
        format.setString(MediaFormat.KEY_MIME, AUDIO_MIME_TYPE);
        format.setInteger(MediaFormat.KEY_SAMPLE_RATE, AUDIO_SAMPLE_RATE);
        format.setInteger(MediaFormat.KEY_CHANNEL_COUNT, AUDIO_CHANNEL_COUNT);
        format.setInteger(MediaFormat.KEY_BIT_RATE, AUDIO_BIT_RATE);
        format.setInteger(MediaFormat.KEY_AAC_PROFILE, MediaCodecInfo.CodecProfileLevel.AACObjectLC);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            format.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE, BUFFER_SIZE);
        }
        mEncoder.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        mEncoder.start();

        mMuxer = new MediaMuxer(outputFile.getAbsolutePath(), MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

        ByteBuffer[] encoderOutputBuffers = mEncoder.getOutputBuffers();
        MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();

        mTrackIndex = -1;
        mMuxerStarted = false;

        int sampleRate = AUDIO_SAMPLE_RATE;
        int channelCount = AUDIO_CHANNEL_COUNT;
        long presentationTimeUs = 0;

        while (true) {
            int inputBufferIndex = mEncoder.dequeueInputBuffer(-1);
            if (inputBufferIndex >= 0) {
                ByteBuffer inputBuffer = mEncoder.getInputBuffer(inputBufferIndex);
                inputBuffer.clear();
                int bytesRead = // read audio data into the inputBuffer
                if (bytesRead == -1) { // eof
                    mEncoder.queueInputBuffer(inputBufferIndex, 0, 0, presentationTimeUs,
                            MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                    break;
                } else {
                    int inputBufferCapacity = inputBuffer.capacity();
                    int size = inputBufferCapacity < bytesRead ? inputBufferCapacity : bytesRead;
                    inputBuffer.put(audioData, 0, size);
                    presentationTimeUs = (long) (1_000_000L * bytesRead / (2 * channelCount * sampleRate));
                    mEncoder.queueInputBuffer(inputBufferIndex, 0, size, presentationTimeUs, 0);
                }
            }

            int outputBufferIndex = mEncoder.dequeueOutputBuffer(bufferInfo, 0);
            if (outputBufferIndex >= 0) {
                ByteBuffer outputBuffer = encoderOutputBuffers[outputBufferIndex];
                if (!mMuxerStarted) {
                    MediaFormat newFormat = mEncoder.getOutputFormat();
                    mTrackIndex = mMuxer.addTrack(newFormat);
                    mMuxer.start();
                    mStartTime = System.nanoTime();
                    mMuxerStarted = true;
                }
                if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
                    bufferInfo.size = 0;
                }
                if (bufferInfo.size != 0) {
                    outputBuffer.position(bufferInfo.offset);
                    outputBuffer.limit(bufferInfo.offset + bufferInfo.size);
                    mMuxer.writeSampleData(mTrackIndex, outputBuffer, bufferInfo);
                }
                mEncoder.releaseOutputBuffer(outputBufferIndex, false);
            } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                MediaFormat newFormat = mEncoder.getOutputFormat();
                mTrackIndex = mMuxer.addTrack(newFormat);
                mMuxer.start();
                mStartTime = System.nanoTime();
                mMuxerStarted = true;
            }
        }
        release();
    }

    private void release() {
        if (mEncoder != null) {
            mEncoder.stop();
            mEncoder.release();
            mEncoder = null;
        }
        if (mMuxer != null) {
            if (mMuxerStarted) {
                mMuxer.stop();
            }
            mMuxer.release();
            mMuxer = null;
        }
    }
}

注意，这只是一个简单的示例，实际应用中还需要考虑错误处理、音频数据来源和如何停止录制等问题。