Question

我如何打开相机：在终端（我输入的$ prompt =命令后的文本）： _________________

$ ls /dev/video*
/dev/video0  /dev/video1
$ vlc v4l2:///dev/video0
VLC media player 2.0.8 Twoflower (revision 2.0.8a-0-g68cf50b)
[0x9f2d908] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.

VLC开始播放相机输出。

在另一个新终端（BOLD =我输入的命令）：

$ vlc v4l2:///dev/video1
VLC media player 2.0.8 Twoflower (revision 2.0.8a-0-g68cf50b)
[0x9b24908] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
[0xb0500960] v4l2 demux error: VIDIOC_STREAMON failed
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
libv4l2: error setting pixformat: Device or resource busy
[0xb0501188] v4l2 access error: cannot set input 0: Device or resource busy
[0xb0501188] v4l2 access error: cannot set input 0: Device or resource busy
[0xb5300618] main input error: open of `v4l2:///dev/video1' failed

没有播放视频，只播放错误消息。

主要目标：我想在opencv（c ++）中同时打开两个摄像头...与opencv有类似的错误..所以我使用VLC播放器调试问题。使用c ++ opencv同时打开两个摄像头时的错误（代码类似于https://code.ros.org/trac/opencv/browser/trunk/opencv/samples/cpp/starter_video.cpp?rev=4705）

e557822@e557822-T740:~/Desktop/Camera/starter_video2$ ls /dev/video*
/dev/video0  /dev/video1  /dev/video2
e557822@e557822-T740:~/Desktop/Camera/starter_video2$ ./starter_video2 0 1
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
press space to save a picture. q or esc to quit
init done 
opengl support available 
libv4l2: error turning on stream: No space left on device
VIDIOC_STREAMON: No space left on device

更新7/24：这个Ubuntu 12.04（32位）是运行在VMware Fusion上的客户操作系统。这里的主机操作系统是在Mac Pro计算机硬件上运行的OSX 10.9.4。

$ lsusb -t
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
    |__ Port 1: Dev 2, If 0, Class=HID, Driver=usbhid, 12M
    |__ Port 2: Dev 3, If 0, Class=hub, Driver=hub/7p, 12M
        |__ Port 1: Dev 4, If 0, Class='bInterfaceClass 0xe0 not yet handled', Driver=btusb, 12M
        |__ Port 1: Dev 4, If 1, Class='bInterfaceClass 0xe0 not yet handled', Driver=btusb, 12M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci_hcd/6p, 480M
    |__ Port 1: Dev 6, If 0, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
    |__ Port 1: Dev 6, If 1, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
    |__ Port 2: Dev 7, If 0, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
    |__ Port 2: Dev 7, If 1, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
$

Answer 1

这是USB带宽问题，而不是VLC问题。

VIDIOC_STREAMON: No space left on device是USB带宽已满时给出的消息。

大多数现代USB相机都可以进行高速，高密度的图像输出。 USB2限制为480Mbps，理论上为60兆字节/秒。在实践中，所有类型的开销将使用大约一半，并且最多可以获得30兆字节/秒。这意味着相机可以30fps发送1兆字节的图像。

您所能做的就是获得带有多个USB总线的主板。所有小型计算机往往只有一台。高端游戏主板有2..3个USB2.0总线。你可以在linux下看到它：

$ lsusb -t
/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 5000M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 480M
    |__ Port 4: Dev 2, If 0, Class=scard, Driver=usbfs, 12M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci_hcd/2p, 480M
    |__ Port 1: Dev 2, If 0, Class=hub, Driver=hub/8p, 480M
        |__ Port 5: Dev 3, If 0, Class='bInterfaceClass 0xe0 not yet handled', Driver=btusb, 12M
        |__ Port 5: Dev 3, If 1, Class='bInterfaceClass 0xe0 not yet handled', Driver=btusb, 12M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci_hcd/2p, 480M
    |__ Port 1: Dev 2, If 0, Class=hub, Driver=hub/6p, 480M
        |__ Port 3: Dev 3, If 0, Class=vend., Driver=rts5139, 480M
        |__ Port 5: Dev 4, If 0, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
        |__ Port 5: Dev 4, If 1, Class='bInterfaceClass 0x0e not yet handled', Driver=uvcvideo, 480M
$

最有可能两台摄像机都连接到同一总线。

其他选择是降低FPS速度或分辨率。但这并不总是有帮助，因为我已经看过无论如何都能保留80％USB带宽的相机。

在VLC播放器Ubuntu 12.04上同时打开2个USB摄像头

1 个答案: