Wednesday, September 30, 2009

Java Video to FLV (Flash Video) converter using FFmpeg

This post should have been written one or two years ago, with the Exit of YouTube and the big promise of the video content on the internet. But, as with every big buzz, the world has already taken it's next step towards smart phones and social networks.
YouTube and all the other video web sites allow uploading a video file. This video file can be shown on the web using a Flash based video player. The Flash video player can play FLV files. FLV file stands for: Flash Video File, which is a video file quite similar to WMV, MPG, AVI etc'.
So, as you can understand, the basic step towards building your own video site, is knowing to convert uploaded video files from all kinds to FLV. Doing the video conversion is a very complex job, requiring a great knowledge. Luckily for us, there is a great open source project named: FFmpeg, which, among the rest, allows us to convert almost any video from any type to any type. FFmpeg is a cross platform project. Whether you have Linux servers or Windows server (or any other popular operating system), FFmpeg will be available for you.
First, in order to do video conversion, we will have to download FFmpeg. If you are using Windows, you can find on the web compiled version ready for use. I found mine here.
FFmpeg is command line application. It has many options and parameters. In general, in order to convert a video file from any type to FLV we have to run FFmpeg with the following parameters:
ffmpeg -i "C:\filein.mp4" -ar 44100 -s 320x200 -qscale 5 "C:\fileout.flv"

This command takes a file named “filein.mp4” and converts it to FLV video file named: “fileout.flv”. The out video file dimensions is: 320x200. The parameter “qscale” defines the quality of the resulted video. Lower values give better quality. This parameter is not mandatory. Of course that the higher the quality of the video the higher the weight of the resulted file.

We will wrap the FFmpeg command line tool with Java code. We do it by simply executing the above command from Java. This will enable us to convert video to FLV file. These FLV files could be later played by some Flash Video Player (for example , to show the video on the web). A great free Flash based video player is: JW FLV Media Player. It supports many modern features required from a flash player. Some of them are:

  • Full events support allowing to control the video and get notifications from JavaScrip.
  • It allows using plugins.
  • It supports playing a video from any point (just like YouTube).
  • It can play videos directly from YouTube.

These are only some of the features this player has.

Let have a look at out Java Video to FLV converter. It’s code is very simple and straight forward:

public class FLVConverter {
    private String ffmpegApp;
    public FLVConverter(String ffmpegApp) {
        this.ffmpegApp = ffmpegApp;
    public void convert(String filenameIn, String filenameOut, int width, int height) throws IOException, InterruptedException {
        convert(filenameIn, filenameOut, width, height, -1);
    public int convert(String filenameIn, String filenameOut, int width, int height, int quality)
            throws IOException, InterruptedException {
        ProcessBuilder processBuilder;
        if (quality > -1) {
            processBuilder = new ProcessBuilder(ffmpegApp, "-i", filenameIn, "-ar", "44100",
                    "-s", width + "*" + height, "-qscale", quality + "", filenameOut);
        } else {
            processBuilder = new ProcessBuilder(ffmpegApp, "-i", filenameIn, "-ar", "44100",
                    "-s", width + "*" + height, filenameOut);
        Process process = processBuilder.start();
        InputStream stderr = process.getErrorStream();
        InputStreamReader isr = new InputStreamReader(stderr);
        BufferedReader br = new BufferedReader(isr);
        String line;
        while ((line = br.readLine()) != null) ;
        return process.waitFor();

And here is a small test program that does exactly what the above command line example is doing:

    public static void main(String[] args) throws Exception {
        FLVConverter FLVConverter = new FLVConverter("C:\\Users\\merdok\\IdeaProjects\\dev\\tools\\ffmpeg\\ffmpeg.exe");
        FLVConverter.convert("C:\\filein.mp4", "C:\\fileout.flv", 320, 200, 5);
You can also download the converter here.


  1. Thank you for the read and source

  2. thank's for this code it will definatly be useuful for making all vedio converter

  3. I used this code for converting to mp4,its working fine,Is this write way.Please suggest me.

  4. thank's for this code, can we detrmine lenght ,width and format for any type the video