Computing change in phase of a signal using hilbert transform

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Anisia Anil 2023-9-14

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回答： Balaji 2023-9-22

How do I compute the change in phase of a signal using hilbert transform? My input signal is a video, so i want to compute the phase change from frame to frame.

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Answer 1

Balaji 2023-9-22

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Hi Anisia

I Understand that you want to find the phase shift in the of the Hilbert transform of an input video.

For that I suggest you do the following steps:

Read the video file and convert the frames into a grayscale.
Apply Hilbert transform using the ‘hilbert’ function in MATLAB.
Calculate the phase angle in MATLAB using the ‘angle’ function
Find out the difference between the two phases.

Here is a reference code:

% Read the video 
video = VideoReader('video.mp4'); 
%Define two frames to be compared 
index1 = 15; 
index2 = 20; 
%Read the corresponding frames 
frame1 = read(video, index1); 
frame2 = read(video, index2); 
signal1 = rgb2gray(frame1); 
signal2 = rgb2gray(frame2); 
% Apply the Hilbert transform 
analyticSignal1 = hilbert(signal1); 
analyticSignal2 = hilbert(signal2); 
% Extract the phase angle 
phase1 = angle(analyticSignal1); 
phase2 = angle(analyticSignal2); 
%Calculate the phase difference 
phaseDifference = phase1 - phase2; 