有沒有辦法控制pygame中的網絡攝像頭焦點？

Question

我有兩個網絡攝像頭，我想拍照。 以下代碼實現了：

import pygame
import pygame.camera
from datetime import datetime
import Image
import threading
import time

class Camera (threading.Thread):
    def __init__(self, camera):
        self.camera = pygame.camera.Camera(camera,(2304,1536))
        self.stop = False
        threading.Thread.__init__(self)

    def run(self):
        self.camera.start()
        srf = self.camera.get_image()
        img = pygame.image.tostring(srf, 'RGB')
        img = Image.fromstring('RGB', srf.get_size(), img)

        img.save('%s.png'%datetime.now(), 'PNG')

s = datetime.now()

pygame.init()
pygame.camera.init()

cam1 = Camera("/dev/video0")
cam2 = Camera("/dev/video1")

cam1.start()
cam2.start()

cam1.join()
cam2.join()

print datetime.now() - s

但我需要設定焦點。

我找到了這些命令行：

apt-get install uvcdynctrl
uvcdynctrl --device=/dev/video1 --clist
uvcdynctrl --device=/dev/video1 --get='Focus, Auto'
uvcdynctrl --device=/dev/video1 --set='Focus, Auto' 0
uvcdynctrl --device=/dev/video1 --set='Focus (absolute)' 20

我雖然可以使用以下內容：

import os
os.system('command to set the focus')

但在我的（羅技）相機上它不起作用，我從命令行（Ubuntu 12.04，python 2.7）獲得此輸出：

uvcdynctrl --device=/dev/video1 --set='Focus, Auto' 0

[libwebcam] Unsupported V4L2_CID_EXPOSURE_AUTO control with a non-contiguous 
  range of choice IDs found
[libwebcam] Invalid or unsupported V4L2 control encountered: ctrl_id = 0x009A0901, name = 'Exposure, Auto'
[libwebcam] Unsupported V4L2_CID_EXPOSURE_AUTO control with a non-contiguous 
  range of choice IDs found
[libwebcam] Invalid or unsupported V4L2 control encountered: ctrl_id = 0x009A0901, name = 'Exposure, Auto'

編輯：

相機是Logitech HD Pro Webcam C920並運行：

uvcdynctrl --device=/dev/video1 --clist

給出輸出：

[libwebcam] Unsupported V4L2_CID_EXPOSURE_AUTO control with a non-contiguous 
  range of choice IDs found
[libwebcam] Invalid or unsupported V4L2 control encountered: ctrl_id = 0x009A0901, name = 'Exposure, Auto'
[libwebcam] Unsupported V4L2_CID_EXPOSURE_AUTO control with a non-contiguous 
  range of choice IDs found
[libwebcam] Invalid or unsupported V4L2 control encountered: ctrl_id = 0x009A0901, name = 'Exposure, Auto'
Listing available controls for device /dev/video1:
  Brightness
  Contrast
  Saturation
  White Balance Temperature, Auto
  Gain
  Power Line Frequency
  White Balance Temperature
  Sharpness
  Backlight Compensation
  Exposure (Absolute)
  Exposure, Auto Priority
  Pan (Absolute)
  Tilt (Absolute)
  Focus (absolute)
  Focus, Auto
  Zoom, Absolute

Answer 1

執行此操作

sudo apt-get install v4l-utils

並在python中

os.system('v4l2-ctl -d 0 -c focus_auto=0')
os.system('v4l2-ctl -d 0 -c focus_absolute=250')