September 7, 2009

Elphel and Stanford Frankencamera

by Andrey Filippov

In September 2009 there were multiple publications about the Open Source Frankencamera developed at Stanford (Open-source camera could revolutionize digital photography). It is really nice to have more participants in the rather new area of the open hardware devices, we at Elphel are also excited about the possibilities of the hardware that users can accommodate to their needs without “jail-breaking” or otherwise modifying the firmware against the manufacturers’ intentions, often having to start over again after each firmware update (or hardware release) by the manufacturer, risking to “brick” their gadgets if something goes wrong in the process.

We believe that having the software and hardware designs “free” and “open” is the only sustainable way to deal with ever-increasing complexity of the designs. Model it after the human activity that proved to be capable of dealing with complex matters – modern science that replaced proprietary and secret knowledge of alchemy and like. This is why we applaud achievements in this area that we are working hard ourselves too.

It is important to have good cooperation in such development, sharing ideas, working together on common standards and API. As of today we are still in minority, traditional (proprietary) camera manufacturers are better organized, but the standards they develop are only sub-optimal for the open hardware.

There is no reference to Elphel (or other similar works) in the article itself, it appears in the Frequently asked questions about the Frankencamera. That page among other things compares their current Stanford OMAP-based version of the camera and Elphel prototype used during development:

 Isn’t there already a Linux camera, the Elphel?

Yes there is. In fact, our first Frankencamera prototype was built around an Elphel camera. However, these aren’t really standalone cameras. Once you add a viewfinder and power supply with batteries, you get an awkwardly sized and shaped device. More importantly you get high latency between the sensor and viewfinder. That’s why we switched to a board, based on the TI platform, that includes an LCD touchscreen.

That is correct, we do not have the viewfinder in Elphel cameras and it is not an omission – we try to focus on the core camera parts, leaving visualization to the off-the-shelf gadgets. We believe that others can create “mashups” with appropriate devices. There are many different applications that our users can think about customize our products themselves. In the model 373 we plan to have a second low-res output from the FPGA to simplify viewfinder functionality with low-power devices that fail to render the full resolution/frame rate camera output.

As for the latency – it is really small when using the appropriate video player. The in-camera latency is less than two frames (about 20 scanlines + 1000 pixels in the FPGA – from the sensor port to the compressed bitstream in the system memory buffer and one frame in the buffer before the frame is sent out). When using the MPlayer the host PC latency is also about just one frame that makes it possible to use the camera+PC in real time applications, like a replacement of a rear view mirror in Elphel mobile office

The article says that The imaging chip is taken from a Nokia N95 cell phone but it seems not to be complete. Yes, it may be (and likely is but I do not know for sure – N95 circuit diagram is not posted) the same imaging chip, but according to this posting the sensor front end board is really open source and you can download the documentation (released under GNU FDL license) from Elphel Wiki page

Update:Andrew, thank you for adding information to Frequently asked questions about the Frankencamera .
BTW – we were able to control Canon EOS lenses directly in our model 323C ("C" for "Canon"), we may still have some hardware around. And the code is at Sourceforge – lensraw.html , lensraw.c


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