Unable to do fast I/O of dynamically generated images on a IP camera

Question

Hi,

I have a image file stored at a remote server (i.e http://example.com/images).The images in this folder are getting updated at the rate of 1 image per 100 milliseconds Think of ip cams that transmit MJPEG images .

I am using apache HTTP client api to connect to my remote server .I am getting a stream of the content

HttpClient httpClient = new DefaultHttpClient();
    HttpGet httpget = new HttpGet("http://example.com/images/screenshot.jpg");
    HttpResponse response = httpClient.execute(httpget);
    HttpEntity entity = response.getEntity();
    if (entity != null) {
    InputStream instream = entity.getContent();

I am wrapping up the input stream in BufferedInputStream for faster I/O .But since the images are getting generated at very fast rate and they are on an average 250kb in size.

I would like to use the NIO features like FileChannel as well as MemoryMappedBuffers to improve the I/O performance as well access generated image files on remote server in non blocking mode.

But whatever samples I have seen talk about creating FileInputStream / RandomAccessFiles which take File Object as parameter.

I am getting the InputStream as response from remote server which I am unable to convert to FileInputStream to get FileChannel.

I would like to know if there is any implementation in apache http client api that gives fileChannels.

Or should i explore sockets to get the channel access. I have also exlored javax.imageIO , but not sure if it will meet my requirement of faster I/O

Answer 1

Your limiting factor is going to be the network. If you have a 1mbps line, that means your practical max transfer will probably be about 100 kilobytes per second (I realise 8 bits to the byte, but given communication overhead the typical observed transfer tends to be 10-to-1).

If you're looking to pull down 10 images per second, and each image is 250k, you need a 25 mbps network connection.

Sockets might offer minor improvements, but it will still not achieve what you want. Have you considered compression? E.g. on server, assemble several images into a compressed archive, download, and uncompress. This still will not get you 10 250k images per second, but could get you closer.

Another option may be to use a video stream, unless you absolutely need images.

If you absolutely need 10 images per second, you need to either increase the speed of your connection to the server or reduce the size of the images, or some combination of both.