Hit a hardware limitation with java

whats newxt · 30-06-2015 2:39pm #1

Made a simple screen recording program and it only runs the loop as fast as it can process here the code: http://pastebin.com/S1k7j9mV
Anyone help me out think i need to use more threads.

BrokenArrows · 30-06-2015 3:21pm

You're plan is to write out a PNG image to the disk every 1 second and you have hardcoded a delay of 1 second.

That is a very inefficent way of doing things. Even if you hadnt hardcoded the 1 second delay it would be very ineffecient.

A quick google gave me this project. http://code.google.com/p/java-screen-recorder/ Maybe have a read through the code and it will give you some ideas.

Png. If you want to stick to the PNG capture method you should be converting this PNG to a compressed video stream and saving the video to the disk. The conversion to video should be done on a separate thread so it doesnt slow down the capture loop.

Giblet · 30-06-2015 3:21pm

File IO should be async or use a different thread if possible.
I'm not sure about Java and IO Completion ports though to get "true" async, I'm sure there's a library somewhere. You should also have a buffer to store x frames and reduce writes to disk anyway.

whats newxt · 30-06-2015 3:32pm

I want the images to be in .png format as an image sequence not a video

BrokenArrows · 30-06-2015 4:41pm

whats newxt wrote: »

I want the images to be in .png format as an image sequence not a video

Ok so your requirement is to have a image sequence.
How many images do you want per second. ie. Your framerate?

The overhead involved in writing that many files to the disk of that size is unavoidable. Its going to slow down your system.

I just write a quick program in C# to take a screenshot and save to the disk. I managed to get about 24 images per second using 18% cpu but my disk access went a bit crazy.

whats newxt · 30-06-2015 4:48pm

BrokenArrows wrote: »

Ok so your requirement is to have a image sequence.
How many images do you want per second. ie. Your framerate?

The overhead involved in writing that many files to the disk of that size is unavoidable. Its going to slow down your system.

I just write a quick program in C# to take a screenshot and save to the disk. I managed to get about 24 images per second using 18% cpu but my disk access went a bit crazy.

I need 15 frames a second, was thinking of rewriting it using python to be honest. I know little to nothing about threads

BrokenArrows · 30-06-2015 5:12pm

whats newxt wrote: »

I need 15 frames a second, was thinking of rewriting it using python to be honest. I know little to nothing about threads

Out of curiosity what are you planning to do with the images? Maybe someone can think of a better option for you.

whats newxt · 02-07-2015 2:09pm

So i redid it with python and still have the same problem, it's faster but not 15 FPS fast. Is it just my hardware or what. old i3 on a fairly rubbish laptop. Anyway here the code:

import gtk.gdk
import time

i = 0

print "  ________ _______    _____    "
print " / ____/  |  \__  \  /     \   "
print "< <_|  |  |  // __ \|  Y Y  \  "
print " \__   |____/(____  /__|_|  /  "
print "    |__|          \/      \/   "
print "    |__|          \/      \/   "
print "Screen recorder GNU - GPL V3"

while True:

    
    i += 1
    w = gtk.gdk.get_default_root_window()
    sz = w.get_size()
    print "FRAME: %d OK!"%i 
    pb = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB,False,8,sz[0],sz[1])
    pb = pb.get_from_drawable(w,w.get_colormap(),0,0,0,0,sz[0],sz[1])
    pb.save("Capture %d"%i,"png")

whats newxt · 02-07-2015 2:28pm

Oh, i see changing to jpeg gives me more that 15 frames a second approx 40/50. Thanks for your help though. I guess .png holds alot more data.

Hit a hardware limitation with java

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