How do I add a marker to only specific frames in a video

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I would like to add a visual marker with a fixed position (e.g. top right corner) to my video that is only visible at specific frames. The frames during which I want the marker to be shown are saved in a vector.
Matthias Heuberger
Matthias Heuberger on 22 Sep 2019
Yes, I have an array with all the frames and I know the indices of the frames to mark.

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Accepted Answer

Kavya Vuriti
Kavya Vuriti on 5 Dec 2019
As you know the indices of frames to mark, you can use readFrame function to read those frames from video and then use insertMarker function to add marker to the frame at specific position. If you want to add markers to frames with indices 2, 4 and 6, your code will look something like this:
% Create object to read video
v = VideoReader('xylophone.mp4');
% Frames to which marker must be inserted
markFrames = [2 4 6];
frameidx = 0;
videoPlayer = vision.VideoPlayer;
while hasFrame(v)
% Read next video frame
frame = readFrame(v);
frameidx = frameidx + 1;
% Check if index of frame is to be marked or not
if any(ismember(markFrames, frameidx))
markedFrame = insertMarker(frame, [50 50]);
Hope this helps.
Walter Roberson
Walter Roberson on 28 Feb 2023 at 19:35
My understanding is that the video writing library that MATLAB uses is not the most efficient library, so you might be able to improve performance by using a C++ interface or using loadlibrary() to talk to an external library.

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