Experimental RAW recording

This is taken directly from an update via the crowdfunding site and expalins the thoughts behind the RAW recording adoption :

A lot of the questions we have received are about the "experimental raw" recording that we propose as an AXIOM Beta feature. Now we want to explain what exactly we mean with that.


First the word "experimental" means we have not tested it yet, its a concept, we know others are doing something similar so we are pretty confident it will work, but we can only be sure once we have actually tried for ourselves.


The background behind this idea is that that a raw image actually contains less data than a color image because with a bayer pattern image sensor not every pixel sees every color. The colors get reconstructed in the so called debayering process which typically happens in post production with raw footage.


So in an RGB recording with 8 bits per channel we get 24 bits of space to park our data in for each pixel. Since most recorders do chroma subsampling eg. 4:2:2 that reduces the effectively available space to 16 bit per pixel. Now the trick is to just store a “monochrome” raw pixel in that space, two 12 bit raw pixels fit into one 24 bit RGB 4:4:4 pixel which would allow to eg. record twice the resolution or twice the frame-rate in a traditional 1080p datastream. If your recorder also supports the double frame rate (eg. 1080p60 if you aim for 1080p30) you actually get 4 times the bandwidth. 4K (or actually UHD) has four times as many pixels as HD, so voila that is the experimental 4K raw storage mode.


 


This of course means that the recorded video is not viewable out of the box anymore. Its not actually an image sequence you see when playing back the recording, its a visualization of a datastream. With the right interpretation (which any raw format needs anyway) all the original raw data can be utilized as raw footage. Initially this could be accomplished through a simple file conversion (ffmpeg, custom plugins etc.), and eventually (much sooner than later with community support), be widely adopted by NLEs and raw image/video processing software.

Dan Mulligan

www.rogueelementdigital.com

 

Posted on September 23, 2014 .