使用java将flv文件格式视频转换为mp4文件格式，使用的工具为ffmpeg。

/**
 * 转换视频格式时需要的自定义线程
 */
public class PrintStream extends Thread{
	java.io.InputStream __is = null;
    public PrintStream(java.io.InputStream is) 
    {
        __is = is;
    } 
 
    public void run() 
    {
        try 
        {
            while(this != null) 
            {
                int _ch = __is.read();
                if(_ch != -1) 
                    //System.out.print((char)_ch); 
                	System.out.print("");
                else break;
            }
        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        } 
    }
}

public class ConvertVideoUtils(){
    /**
     * flv转换为mp4
     * @param ffmpegPath    ffmpeg安装路径
     * @param inputPath     需要转换为文件(flv)
     * @param outputPath    转换后得文件(mp4)
     * @return
     */
    private boolean processMp4(String ffmpegPath,String inputPath,String outputPath) {
	    List<String> command = new ArrayList<String>();
	    command.add(ffmpegPath + "ffmpeg");
	    command.add("-i");
	    command.add(inputPath);
	    command.add("-c:v");
	    command.add("libx264");
	    command.add("-mbd");
	    command.add("0");
	    command.add("-c:a");
	    command.add("aac");
	    command.add("-strict");
	    command.add("-2");
	    command.add("-pix_fmt");
	    command.add("yuv420p");
	    command.add("-movflags");
	    command.add("faststart");
	    command.add(outputPath);
	    try {
	        Process videoProcess = new ProcessBuilder(command).redirectErrorStream(true).start();
	
	        new PrintStream(videoProcess.getErrorStream()).start();
	
	        new PrintStream(videoProcess.getInputStream()).start();
	
	        videoProcess.waitFor();
	
	        return true;
	    } catch (Exception e) {
	        e.printStackTrace();
	        return false;
	    }
	}
}