OpenCV 3.0.1 and Android Studio 2.1.1, it's posible to build with API level diferent to 21??

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This problem is making me crazy. I'm using Android Studio with OpenCV for Android 3.1.0 when I build my project with "compileSdkVersion 21" and "targetSdkVersion 21" everything goes right, but if I change this version to 19, the grandle build tells me.

Error:(14, 32) error: package android.hardware.camera2 does not exist Error:(15, 39) error: package android.hardware.camera2.params does not exist Error:(19, 20) error: cannot find symbol class Size Error:(26, 13) error: cannot find symbol class CameraDevice

I need to compile my project for Android 4.4 (API 19) but i don't know how to change OpenCV to use this API version.

Thank you, for your time and your help.