video processing for motion detection
4 ビュー (過去 30 日間)
古いコメントを表示
Saffana Siddiqua
2019 年 12 月 8 日
コメント済み: Saffana Siddiqua
2020 年 1 月 28 日
can i track the motion of a motor from a video? i tried histogram plotting but exporting data is hard
12 件のコメント
採用された回答
Turlough Hughes
2019 年 12 月 8 日
編集済み: Turlough Hughes
2019 年 12 月 11 日
So the method I suggested was to look at a single pixel, though you could also look at a few, or the entire image histogram, up to you. Here I track the R component of the mid pixel of each frame and then find local maxima which are greater than a nominal threshold value.
framerate=29.53; % I don't see how to get this from the video object directly.
threshold=0.15;
v=vision.VideoFileReader('vid.mp4');
c=0;
while ~isDone(v)
c=c+1;
f=step(v);
data(c)=f(360,720,1); % for green just replace the with, data(c)=f(360,720,2);
end
figure(), plot(data)
idx1=find(data(2:end-1) > data(1:end-2) & data(2:end-1) > data(3:end))+1; % find local maxima, 'data2'
data2=data(idx1);
hold on, plot(idx1,data2,'or'); % shows local maxima in plot
idx2=find(data2>threshold); % local maxima satisfying threshold
peakFrame=idx1(idx2);
hold on, plot(peakFrame,data2(idx2),'.k','MarkerSize',15) % shows peaks that pass threshold.
numFrames=peakFrame(end)-peakFrame(1) % number of frames from first to last flash.
revs=length(data2(idx2))-1; % Corresponding number of revolutions.
duration=numFrames/framerate; % numFrames/FramesPerSecond = duration in seconds
rpm=revs/(duration/60)
EDIT: as per comments below.
11 件のコメント
Turlough Hughes
2019 年 12 月 11 日
i cant find any function to determine the framerate with vision.videofilereader.
Neither can I. I took the framerate from looking at file details. Surely there's a way to get it with code but I can't see how. I see you've opened another question on this though.
what if i want to know the intensity of green or blue light in the center pixel
the thing is i will get the duration by multiplying the framerate with number of frames
you get duration from NumberOfFrames/framerate:
. I originally had framerate/NumberOfFrames but had fixed that before my last comment.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/254003/image.png)
その他の回答 (0 件)
参考
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!