Tips & Tutorials

Working with Non-Standard HD Resolutions with Avid DS Nitris

By Victor Wolansky, e3 Post, Alexandria, VA

One of the interesting types of projects that post facilities take on in the commercial space is creation of HD pieces at non-standard resolutions.  These are not simply high-resolution projects at 2K or 4K size, but rather, HD projects targeted for non-standard screen size or intended for display across multiple screens.  For these projects, we use Avid DS Nitris, which aside from being a resolution-independent system, has the compositing, effects and paint capabilities ideal for this work. With the addition of dual link connectivity for 4:4:4 color, we have even more options. 

Here is an example of a non-standard HD project along with some tips on how to get it done.  With good planning and an efficient workflow, we were able to complete this project in two weeks. 

"Kitchen of the Future" for Generel Electric

For their "Kitchen of the Future" exhibit, GE produced a six-minute, multi-screen HD presentation, showing actors interacting in a futuristic kitchen.  GE specifically did not want the display to have a static "videowall" look, so the display was comprised of four vertically positioned plasma screens of different sizes.  Our job was to handle all post production for the video and prepare it for display on the four plasma screens from a 2880 x 1080 HD canvas.  For display, the giant image was carved up into four separate 16:9 720 x 480 video streams (one for each plasma screen), all synchronized with a 4-channel MPG server.

Tip #1 – Plan for post during production

To acquire the giant 2880 x 1080 HD resolution necessary for the display, DP Erich Roland shot the HD image in two parts – a left and right segment, since HDCAM can only accommodate 1920 pixels horizontally.  Both segments were then married in the DS to create the larger HD image size.  

Because the plasmas were all different sizes, we had the additional challenge of scaling the actor as he traveled from one screen to another.  This challenge was handled by creating a Photoshop template of the full image as a “top layer” in the project.  The dimensions of each plasma screen (and their bezels) were then superimposed on that image as a blue print for the final display.  The result was a 2880 x 1080 HD image seamlessly displayed across four plasma panels.

Aside from the display, the video itself was designed to look futuristic and required actors to appear as reflections as they interacted with virtual menus a la Minority Report.  To create this effect, the actors were shot against a greenscreen, and then we flopped everything in post to make the actor look like a reflection.  All this was shot through a 12' wide glass wall with grease pencil marks to guide the actor where to touch for the menus. (The marks were later removed using DS Nitris in post.) 

Tip #2 – Use Avid DNxHD

First off, anyone who works with HD knows it can take up a lot of storage space and can be cumbersome to move around on a network.  For this project, we used the Avid DNxHD codec and had great success.  We were somewhat skeptical because we had never used it on green screen footage, and had a bad experience in the past with other compressed footage.  But we were completely surprised with the quality.  There were no visible compression artifacts, and even when we did some tests with and without the codec, no one was able to tell the difference.  The reduced size of the DNxHD encoded material also enabled faster transfers over the network.  Even though the sequence was only six minutes, with all the layers and renders, and caches, the project ate up almost 90% of our total storage, so without the DNxHD codec, we would have had a real problem.

Tip # 3 – Divide and conquer project segments with reference clips

This project was conceived as five segments or “acts,” each comprised of two HD sequences, one for the two left screens and one for the two right screens.  After finishing each segment, it was then exported as a reference clip to a master sequence where all the pieces and both sides of the complete four panel image were joined in one sequence so that we could previsualize the result before compressing the MPEGs. Since the DS scaled this down in real-time, it literally saved us days.  We could also make changes in the reference clip and have them show up automatically in our master sequence, which was important when responding quickly to changes from our client.

Tip #4 – Use AVI exports

Our project settings were HD 1080p/29.97 fps, which enabled us to downconvert in real-time using DS Nitris’ built-in downconverter and send copies of the progress to the musician and sound engineer.  We were able to quickly export AVI and QuickTime reference files from DS (a six minute sequence took just a few seconds) and then compress it in another computer over the network without duplicating hundreds of gigabytes and tying up time on the DS system.  In addition, when we finished the job and had to compress it to several MPEGs, we only exported a very small reference AVI and loaded it through the network on two other computers to crop, resize, and compress the four SD channels out of the 2880x1080 file.  This process went very fast, and eliminated having to duplicate or export a huge HD file.

Tip #5 – Cut render times and free up resources

Once we received the rough cut (by Sam Green of the Edit Room), we had two weeks to deliver the final show.  With such large file sizes render time was a huge factor.  We had  25 layers in the timeline and an average of 20 nodes on the effect tree of each layer, all rendering in 16- or 32-bits, with some files approaching 4K in size.  With a one minute scene taking almost an hour to render, we couldn’t afford any downtime due to computer or drive failure.

One way that we saved a lot of time was to pre-render all the elements of a composite that we considered finished, using cache nodes.  DS Nitris has a very intelligent render architecture that allows you to render a sequence once and never have to render it again unless you need to make a change.  We also learned that rendering in 16-bits, and sometimes even using 32-bits floating, was necessary to avoid banding in the image.  Storing in 10-bits was a must.

A second way we cut render time was using the DS Remote Processing (RP) system. By simply using a cache node after the effect, and processing the node in the RP, we could continue working on a sequence while the RP did the rendering, and after a few minutes the rendered effect would show up in the timeline ready to play.

Tip #6 – Save time by linking files

A large part of this job was employing and working with linked files.  While one editor was working in the DS animating elements linked from Photoshop files, another artist on another machine was finishing the details of those same files.  As he finished and saved them out, the new files replaced the old content in DS Nitris automatically.  This saved a lot of time and made changes very easy.

About Victor Wolansky, Senior VFX Artist, e3 Post

Victor Wolansky has more than 10 years of commercial experience working for ad agencies such as BBDO and Young and Rubicam.  Originally from Buenos Aires he has worked in Argentina and Chile, and is considered one of the most talented 3D animation and Avid DS Nitris artists in the industry.  Victor uses many plug-ins from Genarts and The Foundry, including Tinder Tools and Keylight.  These tools are the perfect complement for the DS, and make the DS a very powerful compositing system, as well as an editing and conforming tool.