android-camera-hal

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Minimal working V4L2-based Android Camera HAL driver.

HAL version: 3.0 Module version: 2.3 Camera API version: 2

LIMITATIONS

• Supports only one camera

• Tested only on Tegra K1, using one specific camera and a webcam.

• No parameter control, most of the reported specs are hardcoded.

• Resolution detection is limited up to 1920x1080. See availableResolutions() in V4l2Device.cpp.

WORKAROUNDS/BUILD TIME CONFIGURATION

In Android.mk there are some flags which control how the driver works. Some of them might not always work.

LOCAL_CFLAGS += -DV4L2DEVICE_FPS_LIMIT=<NNN>

<NNN> is positive integer. Limits framerate at the driver level. Helps when the kernel's V4L2 driver allows to read the buffers faster than it fills them with a new frames. Comment out to disable the limit.

LOCAL_CFLAGS += -DV4L2DEVICE_BUF_COUNT=<NNN>

<NNN> is a positive integer (4 by default) - V4L2 buffers count.

LOCAL_CFLAGS += -DV4L2DEVICE_PIXEL_FORMAT=V4L2_PIX_FMT_UYVY #LOCAL_CFLAGS += -DV4L2DEVICE_PIXEL_FORMAT=V4L2_PIX_FMT_YUYV

V4L2 source color format.

LOCAL_CFLAGS += -DV4L2DEVICE_OPEN_ONCE

Opens and initializes /dev/video0 during boot time. Comment out to open/close the device when a camera app is opened/closed.

LOCAL_CFLAGS += -DV4L2DEVICE_USE_POLL

Use poll() before dequeueing a buffer.

BOOT TIME CONFIGURATION

The "ro.camera.v4l2device.resolution" system property allows to force one single resolution (must be supported by V4L2). The value is in the "WIDTHxHEIGHT" format.

HOW TO BUILD

In your target's makefile (e.g. device/mycompany/mydevice/mydevice.mk) add:

PRODUCT_PACKAGES += camera.$(TARGET_BOARD_PLATFORM) PRODUCT_PACKAGES += media_profiles.xml

and just build Android.