MediaCodec 解析MP4 并自行播放video和audio

具体的demo代码放在码云：https://gitee.com/Lemniscate/audio_and_video_demo

解析的过程类似于上一节分离MP4：https://www.jianshu.com/p/1ceef353ede0
步骤主要是拿到音轨，拿到format 信息，用MediaCodec 解析并将数据喂到相对应的地方

以下是解析音频代码：

private class AudioThread extends Thread {
        private AudioTrack audioTrack;
        private int audioInputBufferSize;
        private int audioTrackIndex;

        @Override
        public void run() {
            MediaExtractor mediaExtractor = new MediaExtractor();
            MediaCodec mediaCodec = null;
            try {
                mediaExtractor.setDataSource(inputFilePath);
                audioTrackIndex = 0;

                for (int i = 0; i < mediaExtractor.getTrackCount(); i++) {
                    MediaFormat trackFormat = mediaExtractor.getTrackFormat(i);
                    String string = trackFormat.getString(MediaFormat.KEY_MIME);
                    if (string.startsWith("audio/")) {
                        audioTrackIndex = i;
                        break;
                    }
                }

                MediaFormat trackFormat = mediaExtractor.getTrackFormat(audioTrackIndex);
                mediaExtractor.selectTrack(audioTrackIndex);

                int audioChannelCount = trackFormat.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
                int audioSampleRate = trackFormat.getInteger(MediaFormat.KEY_SAMPLE_RATE);
                int minBufferSize = AudioTrack.getMinBufferSize(audioSampleRate,
                        (audioChannelCount == 1 ? AudioFormat.CHANNEL_OUT_MONO : AudioFormat.CHANNEL_OUT_STEREO),
                        AudioFormat.ENCODING_PCM_16BIT);
                int maxInputSize = trackFormat.getInteger(MediaFormat.KEY_MAX_INPUT_SIZE);
                audioInputBufferSize = minBufferSize > 0 ? minBufferSize * 4 : maxInputSize;
                int frameSizeInBytes = audioChannelCount * 2;
                audioInputBufferSize = (audioInputBufferSize / frameSizeInBytes) * frameSizeInBytes;

                audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, audioSampleRate,
                        (audioChannelCount == 1 ? AudioFormat.CHANNEL_OUT_MONO : AudioFormat.CHANNEL_OUT_STEREO),
                        AudioFormat.ENCODING_PCM_16BIT, minBufferSize * 4, AudioTrack.MODE_STREAM);

                audioTrack.play();

                mediaCodec = MediaCodec.createDecoderByType(trackFormat.getString(MediaFormat.KEY_MIME));
                mediaCodec.configure(trackFormat, null, null, 0);


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

            if (mediaCodec == null) {
                return;
            }

            mediaCodec.start();

            ByteBuffer[] buffers = mediaCodec.getOutputBuffers();
            int capacity = buffers[0].capacity();
            if (capacity <= 0) {
                capacity = audioInputBufferSize;
            }
            byte[] mAudioOutTempBuf = new byte[capacity];

            MediaCodec.BufferInfo audioBufferInfo = new MediaCodec.BufferInfo();
            ByteBuffer[] inputBuffers = mediaCodec.getInputBuffers();
            ByteBuffer[] outputBuffers = mediaCodec.getOutputBuffers();

            boolean isAudioEos = false;
            long startMs = System.currentTimeMillis();

            while (!Thread.interrupted()) {
                if (!isPlaying) {
                    continue;
                }
                if (!isAudioEos) {
                    isAudioEos = putBufferToCoder(mediaExtractor, mediaCodec, inputBuffers);
                }

                int outputBufferIndex = mediaCodec.dequeueOutputBuffer(audioBufferInfo, TIMEOUT_US);
                switch (outputBufferIndex) {
                    case MediaCodec.INFO_OUTPUT_FORMAT_CHANGED:
                        MediaFormat format = mediaCodec.getOutputFormat();
                        audioTrack.setPlaybackRate(format.getInteger(MediaFormat.KEY_SAMPLE_RATE));
                        break;
                    case MediaCodec.INFO_TRY_AGAIN_LATER:
                        break;
                    case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED:
                        outputBuffers = mediaCodec.getOutputBuffers();
                        break;
                    default:
                        ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
                        sleepRender(audioBufferInfo, startMs);
                        if (audioBufferInfo.size > 0) {
                            if (mAudioOutTempBuf.length < audioBufferInfo.size) {
                                mAudioOutTempBuf = new byte[audioBufferInfo.size];
                            }
                            outputBuffer.position(0);
                            outputBuffer.get(mAudioOutTempBuf, 0, audioBufferInfo.size);
                            outputBuffer.clear();
                            if (audioTrack != null) {
//                                audioTrack.write(mAudioOutTempBuf, 0, audioBufferInfo.size);//用这个写法会导致少帧？
                                audioTrack.write(mAudioOutTempBuf, audioBufferInfo.offset, audioBufferInfo.offset + audioBufferInfo.size);
                            }
                        }
                        mediaCodec.releaseOutputBuffer(outputBufferIndex, false);
                        break;
                }

                if ((audioBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                    //stream end
                    break;
                }
            }

            mediaCodec.stop();
            mediaCodec.release();
            mediaExtractor.release();
            audioTrack.stop();
            audioTrack.release();

        }
    }

解析视频的代码:

private class VideoThread extends Thread {
        @Override
        public void run() {
            MediaExtractor mediaExtractor = new MediaExtractor();
            MediaCodec videoCodec = null;
            try {
                mediaExtractor.setDataSource(inputFilePath);

                int videoTrackIndex = 0;
                int trackCount = mediaExtractor.getTrackCount();
                for (int i = 0; i < trackCount; i++) {
                    MediaFormat trackFormat = mediaExtractor.getTrackFormat(i);
                    if (trackFormat.getString(MediaFormat.KEY_MIME).startsWith("video/")) {
                        videoTrackIndex = i;
                        break;
                    }
                }

                //infomation
                MediaFormat trackFormat = mediaExtractor.getTrackFormat(videoTrackIndex);
                int width = trackFormat.getInteger(MediaFormat.KEY_WIDTH);
                int height = trackFormat.getInteger(MediaFormat.KEY_HEIGHT);
                float time = trackFormat.getLong(MediaFormat.KEY_DURATION) / 1000000;

                mediaExtractor.selectTrack(videoTrackIndex);

                videoCodec = MediaCodec.createDecoderByType(trackFormat.getString(MediaFormat.KEY_MIME));
                videoCodec.configure(trackFormat, surfaceView.getHolder().getSurface(), null, 0);
            } catch (IOException e) {
                e.printStackTrace();
            }

            if (videoCodec == null) {
                return;
            }
            videoCodec.start();

            MediaCodec.BufferInfo videoBufferInfo = new MediaCodec.BufferInfo();
            ByteBuffer[] inputBuffers = videoCodec.getInputBuffers();

            boolean isVideoEos = false;

            long startMs = System.currentTimeMillis();
            while (!Thread.interrupted()) {
                if (!isPlaying) {
                    continue;
                }
                //将资源传递到解码器
                if (!isVideoEos) {
                    isVideoEos = putBufferToCoder(mediaExtractor, videoCodec, inputBuffers);
                }
                int outputBufferIndex = videoCodec.dequeueOutputBuffer(videoBufferInfo, TIMEOUT_US);
                switch (outputBufferIndex) {
                    case MediaCodec.INFO_OUTPUT_FORMAT_CHANGED:
                        break;
                    case MediaCodec.INFO_TRY_AGAIN_LATER:
                        break;
                    case MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED:
                        //outputBuffers = videoCodec.getOutputBuffers();
                        break;
                    default:
                        //直接渲染到Surface时使用不到outputBuffer
                        //ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
                        //延时操作
                        //如果缓冲区里的可展示时间>当前视频播放的进度，就休眠一下
                        sleepRender(videoBufferInfo, startMs);
                        //渲染
                        videoCodec.releaseOutputBuffer(outputBufferIndex, true);
                        break;
                }

                if ((videoBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                    //buffer stram end
                    break;
                }
            }

            videoCodec.stop();
            videoCodec.release();
            mediaExtractor.release();

        }
    }