OpenMV Update: 25FPS Face Detection, USB Support and More

So I've been working on OpenMV for the past week and this is what I have so far:

USB Support:

The camera now supports USB OTG full speed, I've also written a small userspace tool with libusb/SDL to interface with the camera and view the frame buffer, this makes it really easy to debug the image processing code, and it also lets you change the sensor's registers while watching the results in realtime.

I've mentioned building the STM32F4xx libraries in a previous post, you can checkout the repo linked there if you want to build the libraries.

Face Detection:

Many were very interested in this feature, well I've managed to get the viola-jones face detector working on the camera, and it's working fine.. For those of you familiar with the detector, the haar cascade is exported as a C header which is linked to the binary and loaded into the CCM (Core Coupled Memory) a 64KB memory block connected directly to the core. Only one integral image is pre-computed and allocated on the heap, the other one, the squared integral image, which is used for computing the standard deviation, can't fit into memory for the QQVGA resoultion, and so, instead, the standard deviation is computed on the fly for every detection scale using some SIMD instructions to speed it up a bit.

The memory can hold up to 23 stages, however, using only 12 stages and with a relatively large scale step, the detector is working great, with occasional false detections of course, more stages can be used if greater accuracy is required, but not without some performance penalty...As for the numbers, the camera can process 7-8FPS QQVGA, and for QQCIF (88x72) I get 25FPS! 

Here's a video of the face detector in action running at 25FPS:

Here's another video of color tracking running at 30FPS:

Other Updates:
I've been doing some general fixes here and there, mainly to improve the image quality, in addition to that, I've compiled all the libraries and code with optimizations (-O2) and I've seen great improvements in speed, there's also a new pixel format, grayscale, which is basically just the Y channel extracted from the YUV422 to avoid doing that every time a grayscale image is required.

The QCIF/QQCIF are working now (the sensor can output 60FPS when using QQCIF ) and through some other register probing, I've removed a few useless registers and discovered that the sensor has digital zoom, cool!

There's also simple motion detection code in progress, it's based on frame differencing and using the first frame as the background, more work will be done here as soon as I get around to it. And I will probably try template matching next.

I've also just finished a new hardware revision, it has a tiny uSD socket, which I imagine can be used for anything from storing haar cascades, snapshots or video to buffering larger frames, the new revision is also a bit smaller.