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@Hermann-SW
Last active December 9, 2022 12:59
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Allows to always get most recent frame, in case video capture loop has some (computation) delay inside
# Based on: https://stackoverflow.com/questions/43665208/how-to-get-the-latest-frame-from-capture-device-camera-in-opencv/54755738#54755738
#
# Added:
# - configurable delay handling
# - renamed class
# - per frame timestamp output
#
import cv2, threading, time, queue
from sys import argv
wait = 0 if len(argv) == 1 else float(argv[1])
class BufferlessVideoCapture:
def __init__(self, name):
self.cap = cv2.VideoCapture(name)
self.q = queue.Queue()
t = threading.Thread(target=self._reader)
t.daemon = True
t.start()
# read frames as soon as they are available, keeping only most recent one
def _reader(self):
while True:
ret, frame = self.cap.read()
if not ret:
break
if not self.q.empty():
try:
self.q.get_nowait() # discard previous (unprocessed) frame
except queue.Empty:
pass
self.q.put(frame)
def read(self):
return self.q.get()
cap = BufferlessVideoCapture(0)
while True:
time.sleep(wait)
print("after wait, before cap.read()", time.time())
frame = cap.read()
cv2.imshow("frame", frame)
if chr(cv2.waitKey(1)&255) == 'q':
break
@Hermann-SW
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Call with "python BufferlessVideoCapture.py 2" for 2 second delay between loop executions.
Whenever a timestamp message is written, do after a seond a change (eg. of hand) in view.
When next timestamp gets printed, newly displayed frame will show changed scene.

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