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允许多个程序同时访问 /dev/video0？

tag-icon • tag-icon video skype webcam process tox
允许多个程序同时访问 /dev/video0？

我最近才注意到，只要有其他程序访问我的网络摄像头的视频，它就并不总是在程序中播放。

让我们通过一些用法示例来解释这一点：

  1. 我正在运行 uTox（毒我在后台运行一个即时通讯客户端，以便我可以接收来自朋友和客户的安全消息，突然我接到一个 Skype 电话。Skype 无法访问网络摄像头，因为 uTox 已控制该设备。

  2. uTox 正在运行，我想使用 Cheese 检查我的网络摄像头的视频输出。我收到错误：There was an error playing video from the webcam并且没有视频输出。

在这两种情况下，uTox 都不会触发我笔记本电脑上的网络摄像头灯，而且它不应该主动使用网络摄像头（它只是出于某种原因暂停了设备）。为了绕过这个问题，我想知道我是否可以做任何事情让多个程序同时访问摄像头（或者对于熟悉客户端的人来说，我如何从 uTox 中删除对视频的暂停？），因为我通常需要让 uTox 在后台运行。为了接听 Skype 电话而终止进程非常不方便。

有没有任何我可以允许多个程序同时访问同一个视频设备吗？

运行 Cheese 时出错：

$ cheese &
...
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy

(cheese:8259): cheese-WARNING **: Device '/dev/video0' is busy: gstv4l2object.c(2838): gst_v4l2_object_set_format (): /GstCameraBin:camerabin/GstWrapperCameraBinSrc:camera_source/GstBin:bin18/GstV4l2Src:video_source:
Call to S_FMT failed for YU12 @ 1280x720: Device or resource busy

系统信息：

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 15.04
Release:    15.04
Codename:   vivid

# lshw -short
H/W path         Device     Class          Description
======================================================
                            system         Computer
/0                          bus            Motherboard
/0/0                        memory         7873MiB System memory
/0/1                        processor      Intel(R) Core(TM) i5-3337U CPU @ 1.80GHz
/0/100                      bridge         3rd Gen Core processor DRAM Controller
/0/100/2                    display        3rd Gen Core processor Graphics Controller
/0/100/14                   bus            7 Series/C210 Series Chipset Family USB xHCI Host Controller
/0/100/14/0      usb2       bus            xHCI Host Controller
/0/100/14/1      usb1       bus            xHCI Host Controller
/0/100/16                   communication  7 Series/C210 Series Chipset Family MEI Controller #1
/0/100/1a                   bus            7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2
/0/100/1a/1      usb3       bus            EHCI Host Controller
/0/100/1a/1/1               bus            Integrated Rate Matching Hub
/0/100/1a/1/1/1             communication  Bluetooth wireless interface
/0/100/1a/1/1/3             multimedia     HD WebCam
/0/100/1b                   multimedia     7 Series/C210 Series Chipset Family High Definition Audio Controller
/0/100/1c                   bridge         7 Series/C210 Series Chipset Family PCI Express Root Port 1
/0/100/1c/0      eth0       network        NetXtreme BCM57786 Gigabit Ethernet PCIe
/0/100/1c/0.1               generic        BCM57765/57785 SDXC/MMC Card Reader
/0/100/1c.1                 bridge         7 Series/C210 Series Chipset Family PCI Express Root Port 2
/0/100/1c.1/0    wlan0      network        QCA9565 / AR9565 Wireless Network Adapter
/0/100/1d                   bus            7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1
/0/100/1d/1      usb4       bus            EHCI Host Controller
/0/100/1d/1/1               bus            Integrated Rate Matching Hub
/0/100/1f                   bridge         HM77 Express Chipset LPC Controller
/0/100/1f.2                 storage        7 Series Chipset Family 6-port SATA Controller [AHCI mode]
/0/100/1f.3                 bus            7 Series/C210 Series Chipset Family SMBus Controller
...

请注意，此处涉及的视频设备是lshw位于/dev/video0

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