把一个音视频文件的视频部分抽取出来播放

最新推荐文章于 2024-06-12 23:54:59 发布

BetterDaZhang

最新推荐文章于 2024-06-12 23:54:59 发布

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分类专栏： Android 多媒体编程文章标签： android 视频文档结构技术

本文链接：https://blog.youkuaiyun.com/zhang_jun_ling/article/details/52782474

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本文详细介绍如何使用Android的MediaCodec和MediaExtractor进行视频文件的解码与播放。通过具体示例代码展示了创建SurfaceView，利用MediaExtractor从视频文件中提取视频流，并使用MediaCodec进行解码的过程。

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知识结构

MediaCodec： Android中直播视频技术探究之—基础知识大纲介绍、MediaCodec文档翻译
详细介绍了MediaCodec的用法；在这里我们只使用MediaCodec的解码的功能；
mMediaCodec.configure(mMediaFormat, mSurface, null, 0)；我们把SurfaceView.getSurface()传给它，就能把视频在SurfaceView上播放；

MediaExtractor：实现把一个音频文件的视频抽取出来这里已经详细介绍了MediaExtractor的用处，这里不再累述；

步骤

1、创建一个SurfaceView

mSurfaceView = (SurfaceView) this.findViewById(R.id.mSurfaceView);
mSurfaceView.getHolder().addCallback(this);

2、在SurfaceView的Surface创建成功后开启一个线程执行MediaExtractor抽取视频，在MediaCodec进行解码；

public void surfaceCreated(SurfaceHolder holder) {

    }
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        mSurfaceHolder = holder;
        if(null == mPlayerThread){
            mPlayerThread = new Thread(new PlayerRunnable(mSurfaceHolder.getSurface()));
            mPlayerThread.start();
        }
    }
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        if(null != mPlayerThread){
            mPlayerThread.interrupt();
        }
    }

3、最重要的：MediaExtractor与MediaCodec的组合

private class PlayerRunnable implements Runnable{
        private MediaExtractor mMediaExtractor;
        private MediaCodec mMediaCodec;
        private Surface mSurface ;

        public PlayerRunnable(Surface surface) {
            this.mSurface = surface;
        }

        @Override
        public void run() {
            try {
                mMediaExtractor = new MediaExtractor();

                String filePath = new File(Environment.getExternalStorageDirectory(), "/input.mp4").getPath();
                mMediaExtractor.setDataSource(filePath);

                int trackCount = mMediaExtractor.getTrackCount();
                for(int i=0; i<trackCount; i++){
                    MediaFormat mMediaFormat = mMediaExtractor.getTrackFormat(i);
                    String mime = mMediaFormat.getString(MediaFormat.KEY_MIME);
                    if(mime.startsWith("video/")){
                        mMediaExtractor.selectTrack(i);
                        mMediaCodec = MediaCodec.createDecoderByType(mime);
                        mMediaCodec.configure(mMediaFormat, mSurface, null, 0);
                        break;
                    }
                }

                if(null == mMediaCodec){
                    Log.d("MainActivity","dont't find mediaformat info;");
                    return ;
                }
                mMediaCodec.start();

                ByteBuffer[] inputBuffers = mMediaCodec.getInputBuffers();
                ByteBuffer[] outputBuffers = mMediaCodec.getOutputBuffers();
                boolean isEOS = false;
                BufferInfo info = new BufferInfo();
                long startMs = System.currentTimeMillis();

                while(!Thread.interrupted()){
                    if(!isEOS){
                        int inputBufferIndex = mMediaCodec.dequeueInputBuffer(10000);
                        if(inputBufferIndex >= 0){
                            ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
                            int readSampleSize = mMediaExtractor.readSampleData(inputBuffer, 0);
                            if(readSampleSize < 0){
                                //此时表明Video数据我们已经抽取完毕
                                mMediaCodec.queueInputBuffer(inputBufferIndex, 0, 0, 0,         MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                                isEOS = true;
                            } else {
                                mMediaCodec.queueInputBuffer(inputBufferIndex, 0, readSampleSize, mMediaExtractor.getSampleTime(), 0);
                                mMediaExtractor.advance();
                            }
                        }
                    }

                    int outputBufferIndex = mMediaCodec.dequeueOutputBuffer(info, 10000);
                    switch (outputBufferIndex) {
                    case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED:
                        outputBuffers = mMediaCodec.getOutputBuffers();
                        break;
                    case MediaCodec.INFO_OUTPUT_FORMAT_CHANGED:
                        Log.d("MainActivity", "New format " + mMediaCodec.getOutputFormat());
                        break;
                    case MediaCodec.INFO_TRY_AGAIN_LATER:
                        Log.d("MainActivity", "dequeueOutputBuffer timed out!");
                        break;

                    default:
                        ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
                        while (info.presentationTimeUs / 1000 > System.currentTimeMillis() - startMs) {
                            try {
                                Thread.sleep(10);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                                break;
                            }
                        }
                        mMediaCodec.releaseOutputBuffer(outputBufferIndex, true);
                        break;
                    }

                }
                mMediaCodec.stop();
                mMediaCodec.release();
                mMediaExtractor.release();

            } catch (Exception e) {
                e.printStackTrace();
            }
        } 
    }