First-Ever Video Output Working on Open-Source Axiom Alpha Prototype

by steven schwartzLeave a Comment

The open-source, open-book approach taken by the development team at Apertus with their tagline = “Open Source Cinema” is a refreshing and exciting new approach to video product development.

Sure, it's obvious why the Canons, Sonys and Arris of the world have to operate in secret to safeguard their intellectual property and corporate strategies, but I really get a kick out of how we're privy to each new development on the Axiom Alpha cinema camera -both successes and setbacks are shared openly.

I hope that internet trolls will refrain from criticizing the first moving images from the Alpha sensor – after all it's a prototype and clearly indicated as TEST footage. Instead, acknowledge this milestone and raise a glass to wish the Axiom team nothing but success in their endeavors!

Moving Images from Axiom Alpha Prototype

From Apertus:

We have now resolved the issues we were facing with HDMI video recorders. It turns out that monitors are capable of synchronising to whatever frequency you are supplying them with, making them very tolerant and usable straight out of the box – even with non standard signals. Recorders on the other hand are a lot less flexible when it comes to the frequency of the supplied input signals. It appears that they will stubbornly refuse to do anything unless the supplied input frequency is perfect. Unfortunately, the documentation we've found for this is often in contradiction – some sources define this frequency as standard, whilst others will list a different specification. As a result of this confusion, we've ended up cycling through multiple frequencies, adding a few Hz at a time until an image appeared on the HDMI recording device.

Please note that this footage contains the first basically unprocessed raw (not in original bayer pattern though) image samples ever recorded with the Axiom Alpha prototype. Whilst this is a major milestone, it represents only our first step through the door and into the beginning of the actual tweaking. Also keep in mind that this is TEST footage not captured with the intent to showcase the capabilities of the camera but rather to proof that it is working at all. While we think you can already see some potential in the image quality the video is simply NOT meant to be beautiful yet. As it stands, the video signal output from the Axiom Alpha still carries some flaws.

We have not yet:

  • calibrated the colours of the camera
  • calibrated the white/black point (offsets) and linearization, leading to some vertical streak/curtain effects
  • created a Fixed Pattern Noise (FPN) profile (the Alpha prototype already supports this, however we have not yet found the time to actually conduct the required measurements)
  • There are some red lines at the bottom of the image, this is due to unresolved minor incompatibilities between the Axiom Alpha HDMI output and the utilized recorder
Moving Images from Axiom Alpha Prototype

Moving Images from Axiom Alpha Prototype


Due to the limitations of the HDMI encoder chip implemented on the Zedboard, we are currently outputting a rather exotic colour mode: RGB 2:4:2. This has resulted in 1 pixel colour shifts in some situations, visible as red/blue tints around vertical lines. We are currently investigating alternative modes that eliminate this problem. Please also keep in mind that Youtube re-compresses every video that is uploaded, so even when viewing at 1080p, you will still see noticeable compression artifacts irrespective of how crisp the original video upload might be. Since we are still in the process of tweaking and fine-tuning everything, we don't mind these compression artifacts for now. You can rest assured that as soon as we have a greater selection of artistic footage ready to showcase, we will provide access to high quality online video playback / download of these clips.

Read more about this at Apertus: Moving Images from Axiom Alpha Prototype

(cover photo credit: snap from Apertus)

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