java使用javacv将视频转成另一个视频，并保留原视频的音频

要使用JavaCV将视频转换为另一个视频并保留原视频的音频，可以按照以下步骤进行操作：

1. 导入JavaCV库和其他必要的库。

import org.bytedeco.javacv.*;
import org.bytedeco.opencv.opencv_core.*;

2. 创建FFmpegFrameGrabber对象来读取原始视频文件，并设置音频流的索引。

FFmpegFrameGrabber grabber = new FFmpegFrameGrabber("input.mp4");
grabber.setAudioStream(0);
grabber.start();

3. 创建FFmpegFrameRecorder对象来录制新视频文件，并设置音频编码器和音频流的参数。

FFmpegFrameRecorder recorder = new FFmpegFrameRecorder("output.mp4", grabber.getImageWidth(), grabber.getImageHeight());
recorder.setAudioCodec(avcodec.AV_CODEC_ID_AAC);
recorder.setAudioChannels(grabber.getAudioChannels());
recorder.setAudioBitrate(grabber.getAudioBitrate());
recorder.setAudioQuality(0);
recorder.start();

4. 使用Frame对象循环读取原始视频文件中的每一帧，并将其写入新视频文件。

Frame frame = null;
while ((frame = grabber.grab()) != null) {
    recorder.record(frame);
}

5. 关闭录制器和抓取器对象。

recorder.stop();
grabber.stop();

完整的示例代码如下所示：

import org.bytedeco.javacv.*;
import org.bytedeco.opencv.opencv_core.*;

public class VideoConverter {
    public static void main(String[] args) {
        try {
            // Create FFmpegFrameGrabber object to read the original video file
            FFmpegFrameGrabber grabber = new FFmpegFrameGrabber("input.mp4");
            grabber.setAudioStream(0);
            grabber.start();

            // Create FFmpegFrameRecorder object to record the new video file
            FFmpegFrameRecorder recorder = new FFmpegFrameRecorder("output.mp4", grabber.getImageWidth(), grabber.getImageHeight());
            recorder.setAudioCodec(avcodec.AV_CODEC_ID_AAC);
            recorder.setAudioChannels(grabber.getAudioChannels());
            recorder.setAudioBitrate(grabber.getAudioBitrate());
            recorder.setAudioQuality(0);
            recorder.start();

            // Loop through each frame of the original video file and write it to the new video file
            Frame frame = null;
            while ((frame = grabber.grab()) != null) {
                recorder.record(frame);
            }

            // Stop and release the recorder and grabber objects
            recorder.stop();
            grabber.stop();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}