Android音视频处理之基于MediaCodec合并音视频

Android提供了一个MediaExtractor类，可以用来分离容器中的视频track和音频track，下面的例子展示了使用MediaExtractor和MediaMuxer来实现视频的换音：

private void muxingAudioAndVideo() throws IOException {

    MediaMuxer mMediaMuxer = new MediaMuxer(mOutputVideoPath,

                MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

    // 视频的MediaExtractor

    MediaExtractor mVideoExtractor = new MediaExtractor();

    mVideoExtractor.setDataSource(mVideoPath);

    int videoTrackIndex = -1;

    for (int i = 0; i < mVideoExtractor.getTrackCount(); i++) {

        MediaFormat format = mVideoExtractor.getTrackFormat(i);

        if (format.getString(MediaFormat.KEY_MIME).startsWith("video/")) {

            mVideoExtractor.selectTrack(i);

            videoTrackIndex = mMediaMuxer.addTrack(format);

            break;

        }

    }

    // 音频的MediaExtractor

    MediaExtractor mAudioExtractor = new MediaExtractor();

    mAudioExtractor.setDataSource(mAudioPath);

    int audioTrackIndex = -1;

    for (int i = 0; i < mAudioExtractor.getTrackCount(); i++) {

        MediaFormat format = mAudioExtractor.getTrackFormat(i);

        if (format.getString(MediaFormat.KEY_MIME).startsWith("audio/")) {

            mAudioExtractor.selectTrack(i);

            audioTrackIndex = mMediaMuxer.addTrack(format);

        }

    }

    // 添加完所有轨道后start

    mMediaMuxer.start();

    // 封装视频track

    if (-1 != videoTrackIndex) {

        MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();

        info.presentationTimeUs = 0;

        ByteBuffer buffer = ByteBuffer.allocate(100 * 1024);

        while (true) {

            int sampleSize = mVideoExtractor.readSampleData(buffer, 0);

            if (sampleSize < 0) {

                break;

            }

            info.offset = 0;

            info.size = sampleSize;

            info.flags = MediaCodec.BUFFER_FLAG_SYNC_FRAME;

            info.presentationTimeUs = mVideoExtractor.getSampleTime();

            mMediaMuxer.writeSampleData(videoTrackIndex, buffer, info);

            mVideoExtractor.advance();

        }

    }

    // 封装音频track

    if (-1 != audioTrackIndex) {

        MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();

        info.presentationTimeUs = 0;

        ByteBuffer buffer = ByteBuffer.allocate(100 * 1024);

        while (true) {

            int sampleSize = mAudioExtractor.readSampleData(buffer, 0);

            if (sampleSize < 0) {

                break;

            }

            info.offset = 0;

            info.size = sampleSize;

            info.flags = MediaCodec.BUFFER_FLAG_SYNC_FRAME;

            info.presentationTimeUs = mAudioExtractor.getSampleTime();

            mMediaMuxer.writeSampleData(audioTrackIndex, buffer, info);

            mAudioExtractor.advance();

        }

    }

    // 释放MediaExtractor

    mVideoExtractor.release();

    mAudioExtractor.release();

    // 释放MediaMuxer

    mMediaMuxer.stop();

    mMediaMuxer.release();

}

MediaExtractor的接口比较简单，首先通过setDataSource()设置数据源，数据源可以是本地文件地址，也可以是网络地址：

MediaExtractor mVideoExtractor = new MediaExtractor();

mVideoExtractor.setDataSource(mVideoPath);

然后可以通过getTrackFormat(int index)来获取各个track的MediaFormat，通过MediaFormat来获取track的详细信息，如：MimeType、分辨率、采样频率、帧率等等：

for (int i = 0; i < mVideoExtractor.getTrackCount(); i++) {

    MediaFormat format = mVideoExtractor.getTrackFormat(i);

}

获取到track的详细信息后，通过selectTrack(int index)选择指定的通道：

if (format.getString(MediaFormat.KEY_MIME).startsWith("video/")) {

    mVideoExtractor.selectTrack(i);

    break;

}

指定通道之后就可以从MediaExtractor中读取数据了：

while (true) {

    int sampleSize = mVideoExtractor.readSampleData(buffer, 0);

    if (sampleSize < 0) {

        break;

    }

    // do something

    mVideoExtractor.advance();  // 移动到下一帧

}

在读取结束之后，记得释放资源：

mVideoExtractor.release();

巴特西

Android音视频处理之基于MediaCodec合并音视频

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