Using webcam to record a specific length of video

"I want to record an 8-second video at normal speed using the webcam on my laptop. The requirements are as follows:

1. After opening the camera, Matlab will send a trigger, and then start recording; but I think the camera need a warmup time and I dont know how much it is.
2. Record the subject's movements in 8 seconds;
3. Matlab sends a trigger to end the recording.

%% open camera and record video
clear all;clc;
vobj = videoinput('winvideo', 1);
%% Set Properties for Videoinput Object
vobj.LoggingMode = 'disk&memory';
%% Construct VideoWriter object and set Disk Logger Property
subject_name = 'sl';
v = VideoWriter([date, subject_name,'.avi']);
v.Quality = 50;
v.FrameRate = 60;
vobj.DiskLogger = v;   

%% The experiment process
start(vobj)
% need a code to wait camera warm up; it may be the funtion : wait(vobj,
% waittime);

pause(8); % record a 8s video
%% Stop video
stop(vobj)
% Compute actual Frame Rate
elapsedTime = toc;
framesaq = vobj.FramesAcquired;
ActualFR = framesaq/elapsedTime;
% Delete Object
delete(vobj);

[Harshit Saini]

Refer to the following documentation link to implement the camera warmup time.

https://www.mathworks.com/help/imaq/starting-and-stopping-a-video-input-object.html

Additionally, you can try to implement wait time using the "wait" function as you have mentioned in the comment. A wait time of 3 seconds should be a good starting point.