FrameRate and FramePerTrigger during acquisition and writing into a video-file

Hi,

I don't understand how create a video-file setting the right matching between FrameRate and FramePerTrigger during image acquisition.

I write:

vid = videoinput('winvideo', 1, 'YUY2_640x480'); 

vid.ReturnedColorspace = 'rgb'; 

writerObj= VideoWriter('object.avi');

writerObj.FrameRate = 30; 
open(writerObj); 

set(vid,'TriggerRepeat',Inf);
    vid.FramesPerTrigger = 30; %as frame rate
    start(vid) 

while(vid.FramesAcquired<=500) % Stop after 501 frames

      data = getdata(vid,1); 

      imshow(data)

      writeVideo(writerObj,data);
  end

stop(vid) 

close(writerObj)

close

but it retuns a video file a little bit faster than real motion

[Ria Paul]

ds was very helpful to me..thank u..

Answer 1

[Walter Roberson]

As a general statement:

Usually, provided you have enough buffer memory, then more frames you acquire per trigger, the more efficient the acquisition is -- but then of course you have more latency.

Likewise, if you acquire fewer frames per trigger, you have more acquisition overhead per frame, which can potentially lead to dropping frames.

It is worth keeping in mind that although MATLAB's builtin routines are compiled to machine code, MATLAB itself is an interpreted language, so the higher percentage of the time you are executing MATLAB statements (managing the acquisition process, triggering the acquisition, processing on smaller buffers when aggregating frames into larger buffers might be more efficient), the more likely you are to run out of time and need to drop frames; the acquisition drivers are compiled and can handle interrupts better and so on.