How to make imshow function faster in the for loop?

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William Wang
William Wang 2021 年 12 月 1 日
コメント済み: Walter Roberson 2021 年 12 月 4 日
I want to generate a video in the figure window with its original sound, and I extracted total of 6600 frames from the video and saved them in the folder 'VideoFrames' with name 'p1' to 'p6600'.
Below in the for loop I call imshow to display each frame as they "become" the video, but they still are not at the same pace as the sound.
The imshow function takes most of time to run in the profiler, so it's necessary to improve the step of displaying images.
Below is the part of code:
[Y, Fs] = audioread('FruitVideo.mp4');
sound = audioplayer(Y, Fs); % get the audioplayer object
for j = 1:6600 % total frames are 6600
% get each frame image by using the path name & file in index
imageData = strcat('D:\ProgramFiles\MATLAB\InterDir\NetVideos\VideoFrames\p', num2str(j), '.bmp');
% read each frame image
framImage = imread(imageData);
% display each frame in the loop
imshow(framImage);
% After #40 of frame, playing the sound,
% but the images still generates slower than the sound
if j == 40
sound.play;
end
end

回答 (1 件)

Walter Roberson
Walter Roberson 2021 年 12 月 1 日
To make imshow() faster...
Don't call imshow()
Seriously: imshow() has a lot of overhead.
Instead, call image() once and record the handle. Then each iteration through the loop, set the CData property of the image() object to the new data to be displayed.
Reminder: store your directory name in a variable, and use fullfile() to create the path.
imageData = fullfile(ImageDirectory, "p" + i + ".bmp");
  2 件のコメント
Walter Roberson
Walter Roberson 2021 年 12 月 4 日
[Y, Fs] = audioread('FruitVideo.mp4');
ImageDirectory = 'D:\ProgramFiles\MATLAB\InterDir\NetVideos\VideoFrames';
sound = audioplayer(Y, Fs); % get the audioplayer object
for j = 1:6600 % total frames are 6600
% get each frame image by using the path name & file in index
imageData = fullfile(ImageDirectory, "p" + j + ".bmp");
% read each frame image
framImage = imread(imageData);
% display each frame in the loop
if j == 1
h = image(framImage);
else
h.CData = framImage;
end
drawnow()
% After #40 of frame, playing the sound,
% but the images still generates slower than the sound
if j == 40
sound.play;
end
end

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