Webcam CyberLink Webcam Splitter 0 has already been locked

[ajay154]

when I executed DetectMotionExample.java it give me error::

Exception in thread "main" com.github.sarxos.webcam.WebcamLockException: Webcam CyberLink Webcam Splitter 0 has already been locked
    at com.github.sarxos.webcam.WebcamLock.lock(WebcamLock.java:224)
    at com.github.sarxos.webcam.Webcam.open(Webcam.java:181)
    at com.github.sarxos.webcam.Webcam.open(Webcam.java:147)
    at com.github.sarxos.webcam.WebcamMotionDetector.start(WebcamMotionDetector.java:186)
    at DetectMotionExample.<init>(DetectMotionExample.java:22)
    at DetectMotionExample.main(DetectMotionExample.java:31)

[sarxos]

Hi @ajay154, which webcam capture version are you using?

[ajay154]

@sarxos i am using webcam-capture-0.3.10-RC4 version

[sarxos]

@ajay154, thank you for the clarification. Can you please try with RC6? There were fixes introduced within the locking mechanism after RC4 in regards to #65, #128 and #131.

Please also check if you are not running the same process in parallel - locking mechanism has been created to prevent such situations (when one webcam capture process has camera open and the second one is trying to open it again).

[ajay154]

@sarxos thank you...now its working,but in eclipse
import sun.misc.Signal;
import sun.misc.SignalHandler; gives
"Access restriction: The type Signal is not accessible due to restriction on required library C:\Program Files\Java\jdk1.7.0_45\jre\lib\rt.jar", how to resolve it.
and I want to make a speedcam which can calculate speed of a moving object by taking subsequent snapshots , how to do it.

[sarxos]

HI @ajay154,

Access restriction: The type Signal is not accessible due to restriction on required library C:\Program Files\Java\jdk1.7.0_45\jre\lib\rt.jar

The Signal API is restricted, but it should not give you any errors. This is most likely your Eclipse setting problem - please google for the solution or change the settings as described here.

I want to make a speedcam which can calculate speed of a moving object by taking subsequent snapshots , how to do it.

Well, there are dozens of possible solutions. E.g. the naive one - assume you know the scale ratio between the image size and real view dimension (e.g. 640 px = 2 meters), you can get the COG (center-of-gravity) point of motion detector, which may be used to calculate the distance between two consecutive frames. Let P_COG1(x₁,y₁) be a center-of-gravity point of frame 1 and P_COG2(x₂,y₂) a center-of-gravity point of frame 2, and the distance the object moved on the image is Δ_px = √(|x₂ - x₁|² + |y₂ - y₁|²), which may be translated to view dimension by multiplying by scale factor s defined as s = d_m/d_px [m/px] where d_px and d_m are corresponding distances from image and real view. Multiplication gives you the number of meters per single pixel unit. If you assume that t is a time difference between two snapshots, you can calculate the object speed as v = Δ_px * s / t [m/s]

Please note that this is naive approach and not super accurate - you have to assume that only measured object is moving and its geometry is constant. Otherwise COG will be calculated incorrectly. If you are looking for other, more advanced solution, you may use features tracking, e.g. from awesome OpenIMAJ framework.

To implement naive approach using Webcam Capture API only, you will need to change the WebcamMotionDetector source code so it pass lastMotionTimestamp variable into the WebcamMotionEvent - you will need it to calculate time different. You can of course use this class to write your own motion detector where you pimp your algorithm and drop all unnecessary things from the original one - feel free to experiment - I would do that myself, but have no time lately :( ...

[ajay154]

Thanks,I want to use image difference between consecutive images as it is done here http://morefunscience.blogspot.in/2012/05/calculating-speed-using-webcam.html .

[sarxos]

Yup, exactly the same method, but bounds used instead of COG.

Good luck :)

[UrviT]

How to change the version through maven dependency?
Currently: 0.3.10
How to get RC6 here?