MediaCodec和MediaMuxer API剪切视频demo

以下是一个简单的示例代码，演示如何使用MediaCodec和MediaMuxer API剪切视频。请注意，这只是一个基本示例，实际上需要更多的代码来完成这个任务，例如处理不同的视频格式和编解码器参数等。

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

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

public class VideoClipper {
    private static final String TAG = "VideoClipper";
    private static final String SAMPLE_PREFIX = "video_clip_";
    private static final String SAMPLE_EXTENSION = ".mp4";
    private static final int TIMEOUT_US = 10000;

    public static void clipVideo(String inputVideoPath, long startMs, long endMs) throws IOException {
        File inputFile = new File(inputVideoPath);
        MediaExtractor extractor = new MediaExtractor();
        extractor.setDataSource(inputFile.toString());

        int trackCount = extractor.getTrackCount();
        int videoTrackIndex = -1;
        MediaFormat videoFormat = null;

        // Find the first video track index and its format
        for (int i = 0; i < trackCount; i++) {
            MediaFormat format = extractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            if (mime.startsWith("video/")) {
                videoTrackIndex = i;
                videoFormat = format;
                break;
            }
        }

        if (videoTrackIndex == -1) {
            throw new RuntimeException("No video track found in " + inputVideoPath);
        }

        // Configure the video codec
        MediaCodec videoDecoder = MediaCodec.createDecoderByType(videoFormat.getString(MediaFormat.KEY_MIME));
        videoDecoder.configure(videoFormat, null, null, 0);
        videoDecoder.start();

        // Configure the video muxer
        String outputVideoPath = new File(Environment.getExternalStorageDirectory(),
                SAMPLE_PREFIX + System.currentTimeMillis() + SAMPLE_EXTENSION).getAbsolutePath();
        MediaMuxer muxer = new MediaMuxer(outputVideoPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

        // Copy the video header
        ByteBuffer header = ByteBuffer.allocate(1024);
        videoDecoder.getOutputFormat().getByteBuffer("csd-0").rewind();
        header.put(videoDecoder.getOutputFormat().getByteBuffer("csd-0"));
        header.put(videoDecoder.getOutputFormat().getByteBuffer("csd-1"));
        header.flip();
        int videoTrackIndexOut = muxer.addTrack(videoDecoder.getOutputFormat());

        muxer.start();

        // Extract video frames and write to muxer
        extractor.selectTrack(videoTrackIndex);
        ByteBuffer buffer = ByteBuffer.allocate(1024 * 1024);
        boolean inputDone = false;
        boolean outputDone = false;
        boolean videoDone = false;
        long videoStartTimeMs = -1;
        long videoEndTimeMs = -1;
        while (!outputDone) {
            if (!inputDone) {
                int inputIndex = videoDecoder.dequeueInputBuffer(TIMEOUT_US);
                if (inputIndex >= 0) {
                    ByteBuffer inputBuffer = videoDecoder.getInputBuffer(inputIndex);
                    int sampleSize = extractor.readSampleData(inputBuffer, 0);
                    if (sampleSize < 0) {
                        videoDecoder.queueInputBuffer(inputIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                        inputDone = true;
                    } else {
                        long presentationTimeUs = extractor.getSampleTime();
                        if (videoStartTimeMs == -1) {
                            videoStartTimeMs = presentationTimeUs / 1000;
                        }
                        if (videoEndTimeMs == -1 || presentationTimeUs / 1000 < videoEndTimeMs) {
                            videoDecoder.queueInputBuffer(inputIndex, 0, sampleSize, presentationTimeUs, 0);
                            extractor.advance();
                        } else {
                            inputDone = true;
                        }
                    }
                }
            }

            if (!videoDone) {
                MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
                int outputIndex = videoDecoder.dequeueOutputBuffer(bufferInfo, TIMEOUT_US);
                if (outputIndex >= 0) {
                    if (bufferInfo.flags == MediaCodec.BUFFER_FLAG_END_OF_STREAM) {
                        outputDone = true;
                    } else {
                        ByteBuffer outputBuffer = videoDecoder.getOutputBuffer(outputIndex);
                        buffer.clear();
                        buffer.put(header);
                        buffer.put(outputBuffer);
                        buffer.flip();
                        muxer.writeSampleData(videoTrackIndexOut, buffer, bufferInfo);
                        videoDecoder.releaseOutputBuffer(outputIndex, false);
                        if (videoEndTimeMs == -1 && bufferInfo.presentationTimeUs / 1000 >= endMs) {
                            videoEndTimeMs = bufferInfo.presentationTimeUs / 1000;
                            videoDone = true;
                        }
                    }
                }
            }

            if (inputDone && videoDone) {
                outputDone = true;
            }
        }

        // Release resources
        extractor.release();
        if (videoDecoder != null) {
            videoDecoder.stop();
            videoDecoder.release();
        }
        if (muxer != null) {
            muxer.stop();
            muxer.release();
        }

        Log.i(TAG, "Video clipped and saved to " + outputVideoPath);
    }
}

要使用这个示例代码，只需调用`clipVideo`方法并传入要剪切的视频文件路径、开始时间和结束时间。例如：

try {
    VideoClipper.clipVideo("/sdcard/input.mp4", 10000, 20000);
} catch (IOException e) {
    e.printStackTrace();
}

这将在SD卡根目录下创建一个名为“video_clip_*.mp4”的新视频文件，其中*是当前时间的毫秒级时间戳。这个新文件将是原始视频文件从10秒到20秒的剪辑版本。