使用Python在以太网上实现高FPS直播

Question

I plan on building a ROV and I am working on my video feed atm. I will be using fiber optics for all communications and I am tinkering with opencv to stream a webcam feed with python. I might choose to use IP cameras but I wanted to learn more about how to capture frames from a webcam in python first. Since I didn't know what I was going to use in the end I bought a cheap-as-they-get noname USB webcam just to try and get everything working. This camera feed is going to be used for navigation, a seperate video recorder will probably be used for recording video.

Enough about that, now to my issue. I am getting only 8 FPS when I am capturing the frames but I suspect that is due to the cheap webcam. The webcam is connected to a pcduino 3 nano which is connected to a arduino for controlling thrusters and reading sensors. I never thought of how to utilize hardware in encoding and decoding images, I don't know enough about that part yet to tell if I can utilize any of the hardware.

Do you guys believe it's my web cam that is the bottleneck? Is it a better idea to use a IP camera or should I be able to get a decent FPS using a webcam connected to a pcduino 3 nano capturing frames with opencv or perhaps some other way? I tried capturing frames with Pygame which gave me the same result, I also tried mjpg-streamer.

Im programming in Python, this is the test I made:

import cv2, time
FPS = 0
cap = cv2.VideoCapture(0)

last = time.time()

for i in range(0,100):
    before = time.time()
    rval, frame = cap.read()
    now = time.time()
    print("cap.read() took: " + str(now - before))
    if(now - last >= 1):
        print(FPS)
        last = now
        FPS = 0
    else:
        FPS += 1
cap.release()

And the result is in the line of:

cap.read() took: 0.118262052536
cap.read() took: 0.118585824966
cap.read() took: 0.121902942657
cap.read() took: 0.116680860519
cap.read() took: 0.119271993637
cap.read() took: 0.117949008942
cap.read() took: 0.119143009186
cap.read() took: 0.122378110886
cap.read() took: 0.116139888763
8

Answer 1

The webcam should explicitly state its frame rate in its specifications, and that will definitively tell you whether the bottleneck is the camera.

However, I would guess that the bottleneck is the pcDuino3. Most likely it can't decode the video very fast and that causes the low frame rate. You can try this exact code on an actual computer to verify this. Also, I believe OpenCV and mjpg-streamer both use libjpeg to decode the jpeg frames, so their similar frame rate is not surprising.