要看楼主用啥方式了，ffmepg是可以，不过通过java调用性能很低，我推荐一种
java原生的方式，需要引入jave-1.0.2.jar
File source = new File("C:\\Users\\xfy\\desktop\\工作文档\\2817\\test.avi");
File target = new File("C:\\Users\\xfy\\desktop\\工作文档\\2817\\test__001.flv");
AudioAttributes audio = new AudioAttributes();
audio.setCodec("libmp3lame");
audio.setBitRate(new Integer(64000));
audio.setChannels(new Integer(1));
audio.setSamplingRate(new Integer(22050));
VideoAttributes video = new VideoAttributes();
video.setCodec("flv");
video.setBitRate(new Integer(160000));
video.setFrameRate(new Integer(15));
video.setSize(new VideoSize(400, 300));
EncodingAttributes attrs = new EncodingAttributes();
attrs.setFormat("flv");
attrs.setAudioAttributes(audio);
attrs.setVideoAttributes(video);
Encoder encoder = new Encoder();
encoder.encode(source, target, attrs);
File source = new File("C:\\Users\\xfy\\desktop\\工作文档\\2817\\test_1111.mp4");
File target = new File("C:\\Users\\xfy\\desktop\\工作文档\\2817\\test_1111.avi");// 转MP4
System.out.println(source.length());
AudioAttributes audio = new AudioAttributes();
audio.setCodec("libmp3lame");
audio.setBitRate(new Integer(64000));
audio.setChannels(new Integer(1));
audio.setSamplingRate(new Integer(22050));
VideoAttributes video = new VideoAttributes();
video.setCodec("libxvid");// 转MP4
video.setBitRate(new Integer(180000));// 180kb/s比特率
video.setFrameRate(new Integer(1));// 1f/s帧频，1是目前测试比较清楚的，越大越模糊
EncodingAttributes attrs = new EncodingAttributes();
attrs.setFormat("avi");// 转MP4
attrs.setAudioAttributes(audio);
attrs.setVideoAttributes(video);
Encoder encoder = new Encoder();
long beginTime = System.currentTimeMillis();
try {
// 获取时长
MultimediaInfo m = encoder.getInfo(source);
System.out.println(m.getDuration());
System.out.println("获取时长花费时间是：" + (System.currentTimeMillis() - beginTime));
beginTime = System.currentTimeMillis();
encoder.encode(source, target, attrs);
System.out.println("视频转码花费时间是：" + (System.currentTimeMillis() - beginTime));
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (InputFormatException e) {
e.printStackTrace();
} catch (EncoderException e) {
e.printStackTrace();
}
如果还是不懂可以去我的博客看下
http://blog.csdn.net/xiaopy_0508/article/details/54962386
