Video Production and Hardware: January 2009 Archives

Avid's DNxHD codec and Apple's ProRes are both riffs on the Cineform theme of high-quality digital intermediate codecs for editing.  Both offer more efficient compression than some competitors (especially at larger frame sizes), plus 4:2:2 chroma subsampling (which provides greater color fidelity than DV's 4:1:1 subsampling or MPEG's 4:2:0).  But the advantage of one of the other cool features -- support for 10-bit color depth -- has gone largely misunderstood or overlooked.  [Ed.: Some readers have asked me to emphasize that BOTH DNxHD and ProRes offer 10-bit color depth.  Apologies for any confusion.]

For starters, it's worth pointing out that each of the "extras" that ProRes confers may at first seem irrelevant: after all, broadcast NTSC still (for another month or so) uses YCbCr, and broadcast ATSC and DVB still use a variant of MPEG-2, with all the associated limitations.  Don't be fooled, though. 

Your post process almost inevitably involves changing the source image in some way or another, either through color correction, transitions, or any number of other processes -- and when you have all of the "extra" information in the ProRes picture, you're able to create an edited master that still has more information than you'd need for a "perfect" quality broadcast.  Similarly, you'd never edit in MPEG-2 directly (I hope) -- so using the higher-quality intermediate codec gives your compressor more "wiggle room" as the compressor tries to paint the highest-quality picture for the MPEG-2 transcoding step.

But enough of that ... more on bit depth specifically after the jump.

In Final Cut -- in a lot of different video applications, for that matter -- you may have wondered about Import/Export functions based on XML.  In fact, Apple made a big deal about Final Cut's XML Interchange Format when it first released, and for good reason.

As studios and production houses and newsrooms shift to a digital workflow, more and more pieces of the production process have to "talk about" the same footage.  At one broadcast network where we recently conducted training, the entire workflow -- from ingest to scriptwriting, roughing, package editing, promos, and output -- relied on a central media repository. 

Needless to say, that's a whole lot of pieces of software that need to talk to each other -- and making a separate copy of the source media for every step in the process is inefficient (imagine the extra disk space to hold 6 different copies of the same full HD footage for a 24/7 broadcast), not to mention confusing.