refresh servlet jetty java

Question

I have a video stream from an ip-camera and I want to handle this stream via a Server so i can display it on as many devices (like iPads / Browsers) as I need (camera only has 100Mbit/s so a lot of the devices don't show anything). I have a jetty http-Server running. I wrote a class which gets the stream and converts it to a MjpegFrame:

MjpegFrame = frame; 


        try {
            MjpegInputStream m = new MjpegInputStream(url.openStream());
            MjpegFrame f;
            while ((f = m.readMjpegFrame()) != null) {
                if(!running) break;

                frame = f;
            }
            m.close();
        } catch (IOException e) {
            //some error outputs
        }

get the current frame

 public MjpegFrame getCurrentFrame() {
     return frame;
 }

This works fine. Now I am trying to display it with my Servlet, but here I only get a single photo instead of a stream:

protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //String auth = request.getAuthType();
    //System.out.println("auth:"+auth);
    if(vm != null) {
        MjpegFrame frame = vm.getCurrentFrame();
        if(frame != null) {

            BufferedOutputStream output = null;
            try{
                output = new BufferedOutputStream(response.getOutputStream(), 1024);
                response.reset();
                response.setBufferSize(1024);
                response.setContentType("image/webp");
                response.setHeader("Cache-Control", "max-age=0") ;
                response.setHeader("Accept-Encoding", "gzip, deflate, sdch");


                while(frame != null){


                    response.setContentLength(frame.getContentLength());    

                    output.write(frame.getJpegBytes(), 0, frame.getContentLength());


                    frame = vm.getCurrentFrame();
                }
            }catch(Exception e){
                e.printStackTrace();
            }finally {

            }
        } else {
            System.out.println("No image available...");
        }

    } else {
        System.out.println("Error: VideoMultiplier is not set");
    }

}

Does anyone know what is wrong with my code?

Answer 1

Solved it by myself:

the problem was the Conent-Type

 response.setContentType("image/webp");

I used wireshark to analyse it and realised the response should look different. Anyway, thats my response:

String contentType = "multipart/x-mixed-replace; boundary=--yourboundary";
response.setContentType(contentType); 

and instead of --yourboundary you use the boundary from the camera, or, to make it more flexible, build your own header:

public StringBuffer createHeader(int contentLength) {
    StringBuffer header = new StringBuffer(100);
    header.append("--yourboundary\r\nContent-Type: image/jpeg\r\nContent-Length: ");
    header.append(contentLength);
    header.append("\r\n\r\n");

    return header;
}

and then write it like this:

frame = vm.getCurrentFrame();//here I get my frame of the current image I wanna send

StringBuffer header = createHeader(frame.getJpegBytes().length);


byte[] headerBytes = header.toString().getBytes();

byte[] imageBytes = frame.getJpegBytes();
// create a newImage array that is the size of the two arrays
byte[] newImage = new byte[headerBytes.length + imageBytes.length];
// copy headerBytes into start of newImage (from pos 0, copy headerBytes.length bytes)
System.arraycopy(headerBytes, 0, newImage, 0, headerBytes.length);

// copy imageBytes into end of newImage (from pos headerBytes.length, copy imageBytes.length bytes)
System.arraycopy(imageBytes, 0, newImage, headerBytes.length, imageBytes.length);


output.write(newImage,0,newImage.length);
output.flush();

hope it helps someone. cheers