camera.py

import pyudev
import re
from collections import namedtuple

CameraDetails = namedtuple('CameraDetails',
                           ['name', 'short_name', 'resolutions'])

DEV_PATH_RE = re.compile(".*video4linux/(video[0-9]+)$")

C500_RES = [(800,600)]
C270_RES = [(1280,960), (1280,720), (960,720), (1024,576), (960,544),
            (800,600), (864,480), (800,448), (752,416), (640,480),
            (544,288), (432,240), (352,288), (320,240), (320,176),
            (176,144), (160,120)]

SR_CAMERAS = {(0x046d, 0x0807): CameraDetails('Logitech C500', 'C500',
                                              C500_RES),
              (0x046d, 0x0825): CameraDetails('Logitech C270', 'C270',
                                              C270_RES)}


class Camera(object):
    def __init__(self, id_vendor, id_product, dev_path):
        self.id_vendor = id_vendor
        self.id_product = id_product
        self.id = (id_vendor, id_product)
        self.dev_path = dev_path
        self.details = SR_CAMERAS.get(self.id, None)

    def __repr__(self):
        fmt = "Camera '{c.details.name}' {c.id} on '{c.dev_path}'"
        return fmt.format(c=self)


def find_cameras(just_sr_cams=True):
    context = pyudev.Context()
    devs = context.list_devices(subsystem='video4linux')
    cameras = []

    for camera in devs:
        match = DEV_PATH_RE.match(camera.device_path)
        if not match:
            continue
        dev_path = '/dev/' + match.groups()[0]
        usb_dev = camera.parent.parent
        vendor = usb_dev.attributes['idVendor']
        product = usb_dev.attributes['idProduct']
        cameras.append(Camera(int(vendor, 16), int(product, 16), dev_path))

    return filter(lambda c: not just_sr_cams or c.id in SR_CAMERAS, cameras)


def choose_camera():
    cam = None
    cameras = find_cameras()
    if cameras == []:
        return None

    if len(cameras) == 1:
        cam = cameras[0]
    else:
        print "Choose a camera:"
        fmt = "  [{i}]  '{c.details.name}' on '{c.dev_path}'"
        for i in range(len(cameras)):
            print fmt.format(i=i, c=cameras[i])

        try:
            inp = int(raw_input('>> '))
            if inp < len(cameras):
                cam = cameras[inp]
        except:
            pass
    return cam