Image Acquisition reducing CPU-Load

Hi!

I´d like to reduce my CPU-Load during image Acquisition.

I´m using a Logitech C910 for acquiring images. My Code looks like this:

 function [Vid] = InitCAM()

%%Camera Initialisation
% Get the Videoinput
Vid = videoinput( 'winvideo', 1, 'RGB24_1600x1200');

% Set TriggerConfig to manual
triggerconfig(Vid, 'manual');

% Get only one Frame per Trigger
Vid.FramesPerTrigger = 1;

% Get Image-Data as Grayscale
Vid.ReturnedColorSpace = 'grayscale';

set(Vid, 'SelectedSourceName', 'input1')

%%Get Camera Properties for image acquistition
VidSrc = getselectedsource( Vid);

% Adjust properties of Camera  
VidSrc.BacklightCompensation = 'on';

VidSrc.FrameRate = '5';

VidSrc.ExposureMode = 'auto'; 

VidSrc.FocusMode = 'auto';

VidSrc.Gain = 64;

VidSrc.Pan = 0;

VidSrc.Saturation = 32;

VidSrc.Sharpness = 72;

VidSrc.Tilt = 0;

set(VidSrc,'WhiteBalanceMode','auto');

end

After Initialisation i´m starting a GUI where the acquired frames are displayed in an axes.

%%Start Client: Collecting Images and Data-Management
set(Vid,'TimerPeriod', 0.3, 'TimerFcn','BufferImages(Vid, PMMFClient);');
start(Vid)

The TimerFcn looks like this:

function BufferImages(Vid, PMMFClient)
global CurFrame
global OldFrame
global DifFrame
global once
global OldStatusLine

%%Get the Current Frame vom Camera
CurFrame.Image = getsnapshot(Vid);
PMMFClient.Data(1).Image = CurFrame.Image;

% Set the current Time Stamp for this Frame
t = now;
c = datevec ( t );
s = datestr ( c, 0 );
CurFrame.TimeStamp  = s;
PMMFClient.Data(1).TimeStamp = uint8(CurFrame.TimeStamp);

imagesc( CurFrame.Image, 'Parent', GuiHandles.axes1);
set(GuiHandles.axes1,'YTick',[],'XTick',[]); 

end

I´m using an TimerFcn because i´m doing different image processing things in in the TimerFcn which must be cyclic for each frame.

I want to acquire every 0.3 seconds only one image and process it. My CPU load is now 40% using Intel Core 2Duo 2,8GHZ. For my opinion it´s too much.

Have you any idea reducing the cpu load to do this image acquire?

Many thanks in advance!

Answer 1

[David Tarkowski]

Looking at your code, the following items are likely to be using the bulk of the CPU time in your code:

1. Conversion from RGB to monochrome data.
2. Using imagesc instead of image
3. Calling imagesc on every execution of the TimerFcn callback

You can use the MATLAB profiler to verify this and identify other areas of your code that might also be taking up significant CPU resources.

A couple of thoughts as to how you might reduce the CPU resources needed:

1. The format you are using is 'RGB24_1600x1200', but you are converting to monochrome data. If your camera supports a YCbCr color space such as I420 or UYVY, which many webcams do, you should consider using one of those formats instead. Conversion from YCbCr to monochrome is quicker than conversion from RGB to monochrome. The IMAQHWINFO command will show you the supported formats for your device.
2. This document has some tips on how to speed up image display.

[manoj sambasivam]

Will the image be the same as we convert from rgb to grayscale and Ycbcr format to grayscale?