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Zynq-based ZedBoard + CMOSIS Super35 Image Sensor + Apertus Engineering = Axiom Open 4K Cinema Camera

Xilinx Employee
Xilinx Employee
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With HDTV now firmly inserted into mainstream television, the next video vista is 4K-resolution video—now easily viewed at your local cinema multiplex. There are several big players in the professional and prosumer 4K cinema camera market. A non-exhaustive list includes RED, Phantom, Blackmagic, Sony, and JVC. There’s also a community-based project—now being guided under the corporate name Apertus—with the objective of creating an open 4K digital cinema camera design called Axiom. The Axiom project recently passed a major milestone, producing its first 4K RAW DNG image from a second alpha prototype unit using a Zynq-based ZedBoard to control the camera’s CMOSIS CMV12000 Super35/APS-C video image sensor. Here’s the first image:

 

 

Axion alpha prototpe 4K DNG Image.jpg 

 

The CMOSIS CMV12000 sensor brings a lot of goodness to the video party including a 4096x3072-pixel resolution, the ability to capture 150 frames/sec at full resolution with 10 bits/pixel, and a global shutter (which eliminates an annoying CMOS image-sensor problem known as the “Jello” effect). The downside of this image sensor’s massive imaging capability is that the image data comes rolling out of 64 serial LVDS channels at a maximum rate of 300Mbits/sec per channel. Hence the absolute need for massive I/O and massive parallel processing.

 

That’s where the Xilinx Zynq All Programmable SoC and the Avnet/Digilent ZedBoard enter the picture. The ZedBoard’s LPC FMC connectors can be configured with as many as 34 LVDS pairs, which is about half the total number of required channels to achieve full image-sensor performance but is still good enough to permit video capture at 75 frames/sec so there’s plenty of headroom for the Axion Alpha Prototype camera’s target frame rate of “only” 25 frames/sec.

 

Adopting the ZedBoard made things a lot easier for the project team:

 

“The initial plan was to build a custom image sensor board hosting an FPGA and some interfaces (HD-SDI, USB, etc.). Basically we would have built the entire prototype from scratch. A huge effort and while we had a bit of money from sponsors and partners we were not sure it would be sufficient to actually complete this prototype.

 

Then the Xilinx Zynq (Series 7 FPGA SOC) started to ship around Christmas 2012 and we reevaluated our options. The idea was to use an FPGA evaluation board which already features most of the connectors/interfaces and the accompanying hardware and software drivers for them. This suddenly meant we could build upon an existing foundation rather than reinventing the wheel and starting from scratch. We were thinking of starting off with a Xilinx Zynq evaluation board for $ 1,500 USD, however we then discovered the Zedboard which is pretty much the same thing spec-wise but costing only $400 USD. Both evaluation boards feature a so-called FMC connector (a high density PCB to PCB connector) that can help us reduce the amount of work required for a functioning prototype down to “only” designing a PCB hosting the image sensor.”

 

The Zynq SoC also provides the programmable logic needed to perform real-time image processing. You need that to make a number of corrections to the raw image coming off the sensor. For example, there’s a great description of fixed pattern noise on the Apertus Web site:

 

“The good thing about FPN (fixed pattern noise) is that it's static, its always the same when you create multiple images. This is the result of not all pixels on the image sensors surface being 100% equal and the minor difference in light sensitivity can be noticed in captured images. So, the trick to fix this is rather simple: You measure the sensitivity difference of each pixel and reverse it, since its static you only need to conduct this measurement once when calibrating the camera.”

 

This is precisely the sort of task you don’t want to perform in software because the data rate is far too high. You really want to perform corrections like this in hardware, which is where the Zynq SoC’s programmable logic comes in really handy. Other sorts of image adjustments that are or might be needed include hot-pixel compensation, white and color balance, just to name a few.

 

Here’s a photo of the Axiom Alpha Prototype:

 

 

 Axiom Alpha Prototype.jpg

 

 

The board in the back of the prototype is the Zynq-based ZedBoard.  The lens is a standard Nikon F-mount 35mm lens. The CMOSIS CMV12000 Super35/APS-C video image sensor is sandwiched between the Nikon lens and the ZedBoard.

 

Here’s a block diagram of the Axiom Alpha Prototype camera:

 

 

Axiom Open 4K Digital Cinema Camera Block Diagram.jpg 

 

 

The ZedBoard and its Zynq SoC implement everything below the CMOSIS Super35 image sensor.

 

Even more exciting, perhaps, is the full, modular Axiom Open 4K Digital Cinema Camera concept:

 

 

Axiom Open 4K Digital Camera Concept.jpg 

An open project like this gives a rare public look into the development of cutting-edge imaging technology.

 

The Axiom/Apertus project is looking for all sorts of assistance and participation:

 

“Anyone who is interested in a world with Open Cinema tools is welcome to contribute and help us reach this goal. Your specialized knowledge and time is the most valuable commodity you can donate to the project. This is also not limited to contributing to software or hardware tasks - we need people to deal with management tasks, writing documentation, maintaining and improving our website, writing translations, undertaking graphics design, etc. You can also be a filmmaker or DOP, creating videos or footage for collaborative films and / or provide others in the community with technical support and tips. We will provide important contributors with developer hardware (if you are interested specifically in working with Axiom) when available and possible. Participate in a unique global project: advance technology, open up new possibilities and meet interesting people. Let's shape the future of cinema technology together.”

 

There’s a lot more information on the Apertus Web site. Click here.

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