Web camera accessing the same device

Question

Kfir T Flank 2021-6-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/855810-web-camera-accessing-the-same-device

回答： Nihal 2024-4-25

I am trying to connect 4 web cameras and have all 4 live videos simultaneoulsy. I can connect 3 of the cameras with no issue, but every time I try a 4th camera I get the following error:

Error using videoinput (line 391)

winvideo: Image aquisition device is not functioning. Make sure no other objects or applications are accessing the same device.

each camera works fine, and I can switch which camera I turn on first, but no matter what camera when I try turning on the 4th camera I am always thrown that error.I have checked multiple times and I don't think any other program is trying to access the web cam, I am not sure what to do and would appreciate some help.

here is what my code looks like:

%start of the code here

webcamlist

vid1 = videoinput('winvideo', 1);

f1 = figure('Position', [4 378 560 420]');

vidRes1 = vid1.VideoResolution;

nBands1 = vid1.NumberOfBands;

hImage1 = image(zeros(vidRes1(2), vidRes1(1), nBands1) );

preview (vid1,hImage1);

vid2 = videoinput('winvideo', 2);

f2 = figure('Position', [4 378 560 420]');

vidRes2 = vid2.VideoResolution;

nBands2 = vid2.NumberOfBands;

hImage2 = image(zeros(vidRes2(2), vidRes2(1), nBands2) );

preview (vid2,hImage2);

vid3 = videoinput('winvideo', 3);

f3 = figure('Position', [4 378 560 420]');

vidRes3 = vid3.VideoResolution;

nBands3 = vid3.NumberOfBands;

hImage3 = image(zeros(vidRes3(2), vidRes3(1), nBands3) );

preview (vid3,hImage3);

vid4 = videoinput('winvideo', 4);

f4 = figure('Position', [4 378 560 420]');

vidRes4 = vid4.VideoResolution;

nBands4 = vid4.NumberOfBands;

hImage4 = image(zeros(vidRes4(2), vidRes4(1), nBands4) );

preview (vid4,hImage4);

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Nihal 2024-4-25

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/855810-web-camera-accessing-the-same-device#answer_1447766

The error you're encountering when attempting to connect the fourth webcam suggests a limitation or conflict that could be arising due to several potential reasons. Here are a few steps and considerations that might help you troubleshoot and potentially resolve this issue:

1. USB Bandwidth Limitation

One possible reason for this issue could be the USB bandwidth limitation. Most webcams are USB devices, and USB hubs (including those integrated into computers) have a limited bandwidth that must be shared between all connected devices. When you connect multiple high-resolution webcams, you might exceed the bandwidth capacity of the USB controller.

Solution: Try connecting your webcams to different USB ports that are on different USB controllers. For example, if your computer has both USB 2.0 and USB 3.0 ports, distribute the webcams among these ports. Some desktop computers have USB ports connected to different controllers on the front and back of the case.

2. Power Supply Limitation

USB devices also draw power from their USB connection, and there is a limit to how much power a USB hub or controller can supply.

Solution: If possible, use externally powered USB hubs for some of the webcams to ensure that power supply limitations are not the cause of the problem.

3. Driver or Software Limitation

The driver or software managing the webcams might have a limitation on the number of simultaneous connections.

Solution: Check the documentation for your webcams and the software/drivers you are using to see if there are any known limitations or settings that could be adjusted. Updating your drivers to the latest version could also potentially resolve the issue.

4. Check for Conflicting Software

Make sure that no other software is running that might be accessing the webcams. This includes any background processes or services that might not be immediately obvious, such as virtual camera software, other development environments, or video conferencing tools that could be holding onto a camera even if they're not actively using it.

5. System Resources and Specifications

Ensure your system has sufficient resources (CPU, RAM) to handle multiple video streams. Although this is less likely to be the issue, high-resolution video processing is resource-intensive.

I hope it helps!