MediaCodec 实现硬件转码

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/u011330638/article/details/81053520

关于 MediaCodec 的介绍，可以看官网：MediaCodec | Android Developers，也可以看我的上一篇博客：MediaCodec 实现硬件解码，这里就直接上代码了：

public class HWCodec {

    private static final String TAG = "HWCodec";

    private static final long DEFAULT_TIMEOUT = 10 * 1000;

    private static final int MEDIA_TYPE_VIDEO = 1;
    private static final int MEDIA_TYPE_AUDIO = 2;
    private static final int MEDIA_TYPE_UNKNOWN = 0;

    private static final String MIME_TYPE_AVC = "video/avc";
    private static final String MIME_TYPE_AAC = "audio/mp4a-latm";

    private static int getMediaType(MediaFormat format) {
        String mime = format.getString(MediaFormat.KEY_MIME);
        if (mime.startsWith("video/")) {
            return MEDIA_TYPE_VIDEO;
        } else if (mime.startsWith("audio/")) {
            return MEDIA_TYPE_AUDIO;
        }
        return MEDIA_TYPE_UNKNOWN;
    }

    public static void transcode(String srcFilePath, String dstFilePath) {
        MediaExtractor extractor = null;
        MediaMuxer muxer = null;
        try {
            extractor = new MediaExtractor();
            extractor.setDataSource(srcFilePath);
            muxer = new MediaMuxer(dstFilePath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
            doTranscode(extractor, muxer);
        } catch (IOException e) {
            Log.e(TAG, "doTranscode io exception: " + e.getLocalizedMessage());
        } catch (Exception e) {
            Log.e(TAG, "doTranscode exception: " + e.getLocalizedMessage());
        } finally {
            try {
                if (extractor != null) {
                    extractor.release();
                }

                if (muxer != null) {
                    muxer.stop();
                    muxer.release();
                }
            } catch (Exception e) {
                Log.e(TAG, "doTranscode close exception: " + e.getLocalizedMessage());
            }
        }
    }

    private static void doTranscode(MediaExtractor extractor, MediaMuxer muxer) throws IOException {
        int trackCount = extractor.getTrackCount();
        SparseIntArray trackMap = new SparseIntArray(trackCount);
        for (int i = 0; i < trackCount; ++i) {
            MediaFormat format = extractor.getTrackFormat(i);
            if (getMediaType(format) == MEDIA_TYPE_UNKNOWN) {
                trackMap.put(i, -1);
            } else {
                int trackIndex = muxer.addTrack(format);
                trackMap.put(i, trackIndex);
            }
        }

        muxer.start();
        for (int i = 0; i < trackCount; ++i) {
            int trackIndex = trackMap.get(i);
            if (trackIndex == -1) {
                continue;
            }
            extractor.selectTrack(i);

            MediaFormat format = extractor.getTrackFormat(i);
            int maxBufferSize = format.getInteger(MediaFormat.KEY_MAX_INPUT_SIZE);
            long timeUnit = 0;
            boolean isVideo = getMediaType(format) == MEDIA_TYPE_VIDEO;
            if (isVideo) {
                int framerate = format.getInteger(MediaFormat.KEY_FRAME_RATE);
                timeUnit = 1000 * 1000 / framerate;
            }
            ByteBuffer source = ByteBuffer.allocate(maxBufferSize);
            MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();

            int size;
            while ((size = extractor.readSampleData(source, 0)) >= 0) {
                bufferInfo.offset = 0;
                bufferInfo.size = size;
                bufferInfo.flags = extractor.getSampleFlags();
                // api 24 以上可以封装 b 帧，之前版本的视频帧的 pts 必须是递增的
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N || !isVideo) {
                    bufferInfo.presentationTimeUs = extractor.getSampleTime();
                } else {
                    bufferInfo.presentationTimeUs += timeUnit;
                }
                muxer.writeSampleData(trackIndex, source, bufferInfo);
                extractor.advance();
            }
            extractor.unselectTrack(i);
        }
    }

}

源码已上传到 GitHub