android mp4parser怎样进行视频旋转

MP4Parser 是一个用于解析和操作 MP4 视频文件的 Java 库。要使用它来旋转视频，你需要在解析 MP4 文件之后，修改视频轨道的时间戳和缩放属性。以下是一个简单的示例，展示了如何使用 MP4Parser 旋转视频 90 度：

首先，确保你已经将 MP4Parser 库添加到项目的依赖项中。如果你使用的是 Gradle，可以在 build.gradle 文件中添加以下依赖：

implementation 'com.googlecode.mp4parser:mp4parser:1.5.2'

然后，你可以使用以下代码来旋转视频：

import com.googlecode.mp4parser.AbstractContainer;
import com.googlecode.mp4parser.Container;
import com.googlecode.mp4parser.DataSource;
import com.googlecode.mp4parser.FileDataSource;
import com.googlecode.mp4parser.MediaFormat;
import com.googlecode.mp4parser.Track;
import com.googlecode.mp4parser.VideoFormat;
import com.googlecode.mp4parser.h264.H264Track;
import com.googlecode.mp4parser.util.Matrix;

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

public class MP4Rotate {

    public static void main(String[] args) throws IOException {
        String inputPath = "input.mp4"; // 输入视频文件路径
        String outputPath = "output.mp4"; // 输出视频文件路径
        rotateVideo(inputPath, outputPath, 90); // 旋转角度（顺时针）
    }

    public static void rotateVideo(String inputPath, String outputPath, int degrees) throws IOException {
        Container container = new DefaultContainer(new FileDataSource(inputPath));
        Track videoTrack = null;

        for (Track track : container.getTracks()) {
            if (track.getFormat().equals(MediaFormat.Type.VIDEO)) {
                videoTrack = track;
                break;
            }
        }

        if (videoTrack == null) {
            throw new RuntimeException("No video track found in the input file");
        }

        long startTime = 0;
        long endTime = videoTrack.getSampleDescriptionBox().getSampleEntryTime();
        long duration = endTime - startTime;

        H264Track h264Track = (H264Track) videoTrack;
        ByteBuffer[] samples = h264Track.getSamples();

        for (int i = 0; i < samples.length; i++) {
            ByteBuffer sample = samples[i];
            long time = startTime + (duration * i) / samples.length;

            // Rotate the sample data
            Matrix matrix = Matrix.rotate(degrees);
            byte[] rotatedData = new byte[sample.remaining()];
            matrix.transform(rotatedData, sample.array());
            sample.clear();
            sample.put(rotatedData);

            // Update the sample time
            sample.putLong(0, time);
        }

        // Create a new video track with the rotated samples
        Track rotatedVideoTrack = new H264Track(container.getSampleDescriptionBox(), videoTrack.getSampleEntryTime(), videoTrack.getSampleDuration(), videoTrack.getSampleEntrySize(), videoTrack.getCodecInfo());
        for (int i = 0; i < samples.length; i++) {
            rotatedVideoTrack.addSample(sample);
        }

        // Create a new container with the rotated video track
        Container rotatedContainer = new DefaultContainer(new FileDataSource(outputPath));
        rotatedContainer.addTrack(rotatedVideoTrack);

        // Write the rotated container to the output file
        rotatedContainer.writeContainer(new FileOutputStream(outputPath));
    }
}

这个示例中的 rotateVideo 方法接受输入视频文件路径、输出视频文件路径和旋转角度（顺时针）作为参数。它首先解析输入视频文件，找到视频轨道，然后旋转每个样本数据，并创建一个新的视频轨道。最后，它将旋转后的视频轨道添加到一个新的容器中，并将容器写入输出文件。

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