double frame read

[carterw]

It looks like two image frames are being acquired for every cycle through the scanning loop and the first one is not used.

On line 1326 there is the scanning loop;
while still_scanning: # process camera thread images and calculate speed

Then there's a frame read;
image2 = vs.read() # Read image data from video steam thread instance
And then speed_get_contours() is called, passing in the frame that was read;
grayimage1, contours = speed_get_contours(image2, grayimage1)

But then speed_get_contours() ignores the frame that was passed in and does another read in the while not image_ok: loop.

Was this intentional? It seems like that second frame read could be eliminated.

[pageauc]

function def speed_get_contours(image, grayimage1): Does the contour processing. It receives the current frame image and converts it to grayscale and compares it to previous grayscale array to calculate contours. When finished the previous grayscale array is updated to the most recent grayscale line 1218, that is returned by the function ready for the next loop. This is done to reduce processing and is by design. Anyone can send changes via github push for review if they have an improved method. Claude

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On Tue, Aug 1, 2023 at 3:28 PM Bill Carter ***@***.***> wrote: It looks like two image frames are being acquired for every cycle through the scanning loop and the first one is not used. On line 1326 there is the scanning loop; while still_scanning: # process camera thread images and calculate speed Then there's a frame read; image2 = vs.read() # Read image data from video steam thread instance And then speed_get_contours() is called, passing in the frame that was read; grayimage1, contours = speed_get_contours(image2, grayimage1) But then speed_get_contours() ignores the frame that was passed in and does another read in the while not image_ok: loop. Was this intentional? It seems like that second frame read could be eliminated. — Reply to this email directly, view it on GitHub <#134>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABNPKZEUF4XSCYECYDROSNLXTFKHDANCNFSM6AAAAAA3AHGUJY> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

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[carterw]

Yes I understand what the method does. I was pointing out that speed_get_contours() ignores the incoming frame and performs a second frame read in a loop before a crop is attempted. Maybe the vs.read() could be moved to the bottom of that loop? But if you are happy with it as-is that's fine with me.

[pageauc]

Thanks for your correct explanation.
See speed-cam.py ver 12.01 for updated logic
Claude ...

[carterw]

Thanks for the helpful fix!

[pageauc]

Note 12.02 replaces np.std with np.median for calculating ave speed.

Speed camera is written as an object tracker. I will look at adding an option to use vehicle recognition (opencv haarcascade) that can improve speed calculation.

Claude.