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Webcam (UVC)

A UVC camera streams frames over an isochronous endpoint - the transfer type USB uses for time-sensitive media (it trades guaranteed delivery for guaranteed timing). Advertise a resolution and pixel format, then supply frames - or omit the source and the class generates animated color bars.

A color-bar webcam

import time, usbip
from usbip.device import USBDevice
from usbip.classes.device import UVC

dev = USBDevice(0x1209, 0x0006, product="USBIP Camera")
dev.add(UVC(width=320, height=240, fps=15, formats=("yuyv",)))   # color bars
dev.plug()                                                       # serve it; -> a camera
time.sleep(3600)                                                 # serve (Ctrl-C to stop)

#include <unistd.h>
#include "usbip-device.h"
#include "classes/uvc.h"

int main(void) {
    usbip_device *g = usbip_device_create(0x1209, 0x0006);
    usbip_device_set_strings(g, "USB over IP", "USBIP Camera", "0006");

    uvc_opts opts = {
        .width   = 320,
        .height  = 240,
        .fps     = 15,
        .formats = UVC_HAS_YUYV,
    };
    uvc_add(g, &opts);             /* next_frame NULL -> built-in color bars */
    usbip_device_plug(g, NULL);            /* serve it; -> a camera */
    for (;;) sleep(1);
}

Grab a frame

Once a client has imported the device, the host's in-box UVC driver binds it and it becomes an ordinary camera - every app that lists cameras will offer it, browsers included.

uvcvideo binds it as /dev/video*; ffmpeg and any V4L2 app can capture from it:

v4l2-ctl --list-devices
ffmpeg -f v4l2 -i /dev/videoN -frames:v 1 shot.png

usbvideo.sys binds it. Open the Camera app, or pick it from any app's camera list.

Supplying real frames

To send real pixels, pass a frame source: a callback that fills a buffer with one frame in YUYV (a raw packed format, width*height*2 bytes) or MJPEG (a JPEG per frame) and returns its length.

Isochronous & timing

USB/IP has no bus frame clock, so iso transfers complete as fast as the host asks. For a webcam this is usually fine; audio needs real-time pacing (Sound Card).

Full program: examples/uvc_device.py; in C, examples/device/video/. API: UVC.