Saving Live video input to avi file

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Cordelia David 2019-6-5

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https://ww2.mathworks.cn/matlabcentral/answers/465691-saving-live-video-input-to-avi-file

编辑： Cordelia David 2019-6-6

I'm having trouble recording frames from a live video and saving each frame to a playable avi file. I get the error "Operands to the || and && operators must be convertible to logical scalar values."

I'm using Matlab 2018a version, and the video input is using a frame grabber device with serial and cameralink connection.

% Specifies the Range of Interest 
if exist('ROI','var') % Becomes True if the ROI variable was assigned in the function
    CurROI = vid.ROIPosition; % Specifies Region of Interest(ROI) window
    vid.ROIPosition = [max(0,ROI(1)),max(0,ROI(2)),min(ROI(3),CurROI(3)),min(ROI(4),CurROI(4))]; % Creates boundaries for ROI  window
end
% Creates a video file from an array or file of images
diskLogger = VideoWriter(FileNameVideo,'Uncompressed AVI'); % VideoReader
diskLogger.FrameRate = 10; % Sets the framerate of the recorded and saved avi video file
set(vid,'Timeout',50);
% Starts the video
open(diskLogger);
preview(vid);
start(vid); % Triggers the acquisition of the live video
data = getdata(vid,vid.FramesAvailable,'uint8');
writeVideo(diskLogger,data)
implay(data);
%Close, stop, and end the video
close(diskLogger); % Closes the file the video was saved to 
stop(vid); % Stops the triggering of the live camera feed
stoppreview(vid)

I had an earlier version that showed the same error.

for ii = 1:numFrames % Loops through each frame of the live camera feed saved
    writeVideo(diskLogger, data(:,:,:,ii)); % writes each frame of the live feed to a video file 
end

This replaced the writevideo line. IF there is any solution to this, I need it as soon as possible. Any ideas?

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Cordelia David 2019-6-6

Thank you Walter I'll give this a try!

Cordelia David 2019-6-6

编辑：Cordelia David 2019-6-6

在 MATLAB Online 中打开

After implementing the manual trigger and wait period the software worked very well for some cameras, however sometimes I get the error

Error using imaqdevice/wait (line 120)
WAIT reached its timeout before OBJ stopped running.
Error in Video_File (line 46)
wait(vid,10); % Delays saving video so images have been acquired
Error in InitializationScript (line 57)
Video_File(vid, NumFrames, FileNameVideo, ROI ,Pattern); % Function will play and save the
live camera feed to an avi video file and delete from the Matlab workspace
 

I tried lengthening the wait time period or stopping the video before the wait command, but that doesn't seem to work. Is this a problem with the output of my camera, or with the code?

The code:

diskLogger = VideoWriter(FileNameVideo,'Uncompressed AVI');
diskLogger.FrameRate = 30; % Sets the framerate of the recorded and saved avi video file
set(vid,'Timeout',50);
open(diskLogger);
preview(vid); % Opens a window with a preview of the video
start(vid);   % Starts the video
stoppreview(vid);
trigger(vid); % Triggers the acquisition of the live video
wait(vid,10); % Delays saving video so images have been acquired
data = getdata(vid,vid.FramesAcquired,'uint8');
writeVideo(diskLogger,data)
implay(data);

Edit: After reading information about the command wait() I realized I wasn't acquiring all images I had commanded the triggers to acquire because of a delay between when the camera started sending frames and my code started acquiring and saving it. To fix this, I simply added 100 frames to the number of frames the camera would send, so it was a little extra than what my code would acquire. There's probably a simpler and easier way to do this, but hey, it works.

Thank you for all the help and time @Walter Roberson, your answers helped immensely!

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