I’m currently reading an RTMP stream from localhost RTMP server on Ubuntu 22.04 using the default version of OpenCV installed via apt. When I use ffplay, the stream plays with minimal (almost no) latency using the following command:

ffplay -f live_flv 
    -fast 
    -fflags nobuffer 
    -flags low_delay 
    -strict experimental 
    -vf "setpts=N/30/TB" 
    -noframedrop 
    -i "rtmp://localhost:1935/live"

However, when I attempt to read the same stream with OpenCV, I notice some latency. Here’s the code snippet:

cap = cv2.VideoCapture("rtmp://localhost:1935/live buffer=0")
while cap.isOpened():
    success, frame = cap.read()
    if not success:
        continue
    cv2.imshow("window", frame)
    if cv2.waitKey(1) & 0xFF == ord("q"):
        break
cap.release()
cv2.destroyAllWindows()

Based on some suggestions I found online, I tried setting CAP_PROP_BUFFERSIZE to 1 and added buffer=0 to the stream URL. However, there is still noticeable latency compared to ffplay.

How to achieve the same low (almost no) latency with OpenCV as I do with ffplay?