java怎么给视频文件压缩和加水印

Java可以使用FFmpeg库来压缩视频文件和加水印。以下是一个简单的示例代码：

压缩视频文件：

String inputFilePath = "input.mp4";
String outputFilePath = "output.mp4";
String[] cmd = {"ffmpeg", "-i", inputFilePath, "-c:v", "libx264", "-crf", "20", "-preset", "slow", "-c:a", "copy", outputFilePath};

ProcessBuilder pb = new ProcessBuilder(cmd);
pb.redirectErrorStream(true);
Process p = pb.start();

BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
    System.out.println(line);
}
p.waitFor();

加水印：

String inputFilePath = "input.mp4";
String outputFilePath = "output.mp4";
String watermarkPath = "watermark.png";
String[] cmd = {"ffmpeg", "-i", inputFilePath, "-i", watermarkPath, "-filter_complex", "overlay=10:10", "-codec:a", "copy", outputFilePath};

ProcessBuilder pb = new ProcessBuilder(cmd);
pb.redirectErrorStream(true);
Process p = pb.start();

BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
    System.out.println(line);
}
p.waitFor();

以上代码仅供参考，实际使用中需要根据具体需求进行修改和扩展。同时，需要注意安装FFmpeg库并将其加入系统环境变量中。