Previewing pre recorded video

Question

Koohyar 2020-9-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/591742-previewing-pre-recorded-video

编辑： Madhav Thakker 2020-9-23

采纳的回答： Madhav Thakker

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Hi,

Does anybody knows how can I change the following code to use for a pre-recorded video (mp4).?

i need to preview of a pre-recorded video, not live one!

Thanks.

*i am using matlab R2020a

% Create a video input object.
vid = videoinput('winvideo', 1, 'YUY2_640x480');        
set(vid,'ReturnedColorSpace','grayscale');
% Create a figure window. This example turns off the default
% toolbar, menubar, and figure numbering.
figure('Toolbar','none',...
       'Menubar', 'none',...
       'NumberTitle','Off',...
       'Name','My Preview Window');
% Create the image object in which you want to display 
% the video preview data. Make the size of the image
% object match the dimensions of the video frames.
vidRes = vid.VideoResolution;
nBands = vid.NumberOfBands;
hImage = image( zeros(vidRes(2), vidRes(1), nBands) );
% Display the video data in your GUI.
preview(vid, hImage);

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Answer 1

Madhav Thakker 2020-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/591742-previewing-pre-recorded-video#answer_494776

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Hi Koohyar,

I understand that you want to preview pre-recorded video and not a live one. The preview function requires a video input object which is not possible to create using pre-recorded video file.

VideoReader is used for reading and previewing a pre-recorded mp4 file. I am attaching a snippet from the documentation that does the same.

v = VideoReader('xylophone.mp4');
currAxes = axes;
while hasFrame(v)
    vidFrame = readFrame(v);
    image(vidFrame, 'Parent', currAxes);
    currAxes.Visible = 'off';
    pause(1/v.FrameRate);
end