Streaming Video Over USB is Slower than Streaming to IDE

OpenMV Products
11

So right now we can’t yield from snapshot so coros are useless. Anyway, until double buffering is implemented you can either:

  1. use timers like the following example ( I get 20FPS for VGA and 10FPS for HD)
import sensor, image, time, ustruct
from pyb import USB_VCP, Timer

usb = USB_VCP()
sensor.reset()                   
sensor.set_pixformat(sensor.RGB565) 
sensor.set_framesize(sensor.HD)

img = None
ready = False
size = 0

def timer_callback(timer):
    global img
    global ready
    global size
    # DO NOT allocate memory in this handler.
    if (ready == True):
        usb.send(size)
        usb.send(img)
        ready = False 

tim = Timer(2, freq=100)
tim.callback(timer_callback)

while(True):
    fb = sensor.snapshot()
    if (usb.recv(4, timeout=10) == b'snap'):
        while (ready):
            time.sleep_ms(1)
        img = fb.compressed(quality=50)
        size = ustruct.pack("<L", img.size())
        ready = True
  1. take a look at the pyopenmv.py module and pyopenmv_fb.py in the tools dir, these pretty much implement the same protocol used by the IDE: