Android Webcam Library

This project is an Android library to provide an API to access an external USB webcam that supports UVC. The library provides an in-process service (WebcamManager) so that multiple parts of an application can share the same webcam.

The library also provides an example View that can be used directly in a layout, the WebcamPreview.

Problems?

Instead of an FAQ, if you can't get the library to work, try one of these suggestions. Unfortunately video is fairly non-standard across Android OS builds and web cams, so I can't provide very good support.

I don't have a /dev/video0 on my Android tablet or phone.

You may need to change the device name in code to match what your camera appears as in the filesystem (#5).

My device is missing the kernel drivers.

A tip from Borja:

I write you again because finally i managed to have external webcam working on my device. I's not a v4l2 related problem. I's because samsung devices do not have uvcvideo module in their kernel. All new devices have v4l2 intalled in kernel but not uvcvideo.ko that is the driver (module) to get comunication between linux kernel and uvc compliant web camera. I had to recompile a custom kernel to enable USB_VIDEO_CLASS option. With new kernel i have no problems to get frames from my camera with an app named dashcam. Now i'm going to test openxc/android-webcam to try get video in my app.

I get an error about insufficient permissions on the video device

Make sure the /dev/video0 file has permissions of at least 0660, is owned by the media user and the group camera. Also add the CAMERA permissions to your app's manifest.

NativeWebcamJNI(2427): VIDIOC_DQBUF error 9, Bad file number

Based on #13, try changing this:

// Change this
//*fd = open(dev_name, O_RDWR | O_NONBLOCK, 0);
// To this:
*fd = open(dev_name, O_RDWR);

Dependencies

Android SDK
Android NDK
Android Webcam library
USB Webcam supporting UVC and a 640x480 resolution in the YUYV format.

Installation

Clone the Git repository
Run ndk-build in the android-webcam/android-webcam-library folder to compile the native library
Reference the library from your Android application

With Maven:

To install the library to your local Maven repository, so other apps can reference it:

$ cd android-webcam
$ cd android-webcam-library; ndk-build && cd ..
$ mvn install -pl android-webcam-library -am

Usage

To install the example application, first install the library, then:

$ mvn package android:deploy android:run -pl example

To just display the webcam image, add this to your app's layout:

<com.ford.openxc.webcam.WebcamPreview
        android:id="@+id/cp" android:layout_width="fill_parent"
        android:layout_height="0dip" android:layout_weight="1"/>

If you want to modify the image at all, subclass WebcamPreview and override the run() method to make any modifications to the iamge before rendering it to the canvas. The WebcamManager service has a getFrame() method which returns a Bitmap of the latest frame from the camera.

USB Webcam Support

To use a USB webcam in Android, the kernel must be compiled with V4L2. Many late-model Android versions (4.2 and possibly 4.1/4.0) already have this enabled.

If the file /dev/video0 appears on the device when you plug in a video camera, then you've got V4L2 support.

If you have /dev/video0, check the permissions in adb:

$ adb shell
shell@android:/ $ ls -l /dev/video0
crw-rw---- media    camera    81,   0 2013-02-25 10:31 video0

If the file is at least 0660, owned by the media user with the group camera, you're good to go.

Add the CAMERA permissions to your app's manifest:

<uses-permission android:name="android.permission.CAMERA" />

Tested and Working

Toshiba Thrive 10.1"
Google Nexus 7

Tested and Not Working

Galaxy Nexus (might not have enough power to start webcam)

Custom Kernel

If your Android version and device doesn't have include V4L2 support, you'll need to load a custom Android ROM and configure the kernel with these options:

CONFIG_VIDEO_DEV=y
CONFIG_VIDEO_V4L2_COMMON=y
CONFIG_VIDEO_MEDIA=y
CONFIG_USB_VIDEO_CLASS=y
CONFIG_V4L_USB_DRIVERS=y
CONFIG_USB_VIDEO_CLASS_INPUT_EVDEV=y

Contributors

This project was originally based on a JNI implementation for UVC webcams by neuralassembly.

See the CONTRIBUTORS file for other contributors.

android-webcam

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