15 Nov Avid is Self-Aware – Fast Import
Avid is self-aware.
And while not in the Skynet sort of way, Avid is aware of it’s own. Commonly this is found in a shared user environment (Unity, ISIS). However, it can also be found in terms of raw media.
A little known feature within Avid is the concept of a Fast Import. This complicated term does exactly what is says – it imports media into your Avid faster than a traditional import. However, lately I’ve been frequently asked, “well, why not use AMA? No importing is needed!” Let’s address this before we jump into Fast Importing.
AMA in Media Composer 5 (or as I called it: AMA v 2.0) and above introduced a new feature to the previous incarnation of AMA: The ability to use QuickTime files in your Avid project WITHOUT having to transcode during import. While this is fantastic for instant gratification, it can cause problems during creative edit. Newer, highly compressed codecs (See: RED, 5D / 7D, etc) commonly cannot play in real time inside Avid. This can also lead to problems later – exporting and Digital Cuts are somewhat limited by AMA files.
Best practice is to convert all media into an Avid codec – for HD, it’s a flavor of DNxHD – during import. Avid is then dealing with their own codec. Aside from the excellent quality of their codecs, they also do not break down during post due to renders. So, for several reasons, working in an Avid codec – natively – is an excellent choice.
Back to smelling one’s own.
The straight import process into Avid can be a long one. Not only does the conversion of the file into an Avid codec take a while, it also effectively kills your use of the Avid. The Avid is unusable as the progress bar creeps across the screen. But, if we create a file that is ALREADY in the Avid DNxHD codec, Avid will recognize it as such and skip the transcode process.
Avid will still need to wrap the file into the proper MXF shell to be used effectively – however, this is usually 70% – 80% faster than a traditional straight import.
Geek Sidebar: Avid has always had excellent media management. Maintaining this requires Avid to separate a QuickTime file’s audio and video into separate files, wrapping them appropriately, and placing them inside the ‘Avid MediaFiles’ folder. This process takes time, hence the ‘only’ 80% savings in time.
/end Geek Sidebar
Wunderbar! How do I get my grubby paws on this technique?
- Download the Avid codec onto the machine which will do the encode (or as I call it, pre-encode). It’s free! http://www.avid.com/dnxhd
- On the same machine, open up your encoding software du jour. I am a fan boy of Telestream’s Episode Family (Episode Engine, using multiple computers – Nice!) Other solutions may be Apple’s Compressor, Sorenson Squeeze, etc.
- Choose to encode into a QuickTime Movie (.mov) Typically there is an ‘Options’ or ‘Advanced’ button, which will allow you to dig into the particular settings of the Encoder. You want to choose “Avid DNxHD Codec” from the list.
- You can force FPS, but I typically leave it at ‘Best’. If you want better quality you can select “Multi-Pass” (if your software allows the choice). “Single-Pass” works fine for most applications, and is faster.
- As far as Compressor Depth: 9 times out of 10, this should be at “Millions of Colors”, NOT “Millions of Colors +”. Why? The + allows for an alpha channel, which the Avid DNxHD codec now supports. Unless you desire an Avid DNxHD file which has an alpha channel, disregard this. The Alpha channel will cause a longer encode and a larger file size and is typically not used on media that is camera generated. This also goes hand-in-hand with the option below “Alpha”. Select “None”.
- This one is so important, it gets it’s own number in my list. Color Levels: 709 not RGB. Why?
Rec. 601 and Rec. 709 are color spaces for SD and HD video, respectively. These values translate into Avid in an Y’CbCr color space, which Avid plays nicely with.
- Resolutions: This is where things get hairy. Avid, in an attempt to not confuse people, created DNxHD Codec ‘families” to aid in ease of encoding. Unfortunately, it causes confusion when you get past the topical discussion about it.
Avid has 3 DNxHD Codec Families: DNxHD 36, DNxHD 145, and DNxHD 220. These numbers correspond to the data rates of the family (Mb/sec). However, what may not be obvious is that these data rates vary according to frame rate (23.976, 29.97, etc), however the family remains the same. Thus, 23.976 fps in DNxHD 36 at is indeed 36Mb/s, but 29.97 fps at DNxHD 36 is 45Mb/s.
Avid has gotten better at this, and as you look at the chart below, you’ll see the new numbers reflect the correct data rate. Read for yourself: http://www.avid.com/static/resources/es/documents/dnxhd.pdf.
Here are some (of my) good rules of thumb for each family:
- DNxHD36: Offline quality, not fit for broadcast.
- DNxHD145: Threshold of broadcast quality.
- DNxHD220 or 220x: best quality possible
/end Geek Sidecar
- Start the encode!
- Next, we must start an Avid project (or change the project) to be in the correct format to accurately use the imported files. Click your “Format” Tab and ensure your “Color Space” is set to YCbCr709. It already is? You’re a quick one.
File – Import – Options. Click the Image tab. Make sure that “File Pixel to Video Mapping’ reflects the aforementioned “601 SD or 709 HD” Setting.
- Select the “OMFI / AAF” tab. Make sure the OMFI / AAF options are set to “use the source file’s resolution’. This will ensure Avid doesn’t attempt to cross convert your file! Also, choose what drive the media will be copied and stored to.
- Select your file and Go!
You’re waiting less now, I hope!
I find the speed benefit to be about 80% faster (trials done on a Dual Quad Core 2.93 GHz ‘Nehalem’ MacPro, a Mid 2007 Intel Core Duo 2.4 GHz ‘Merom’ MacBook Pro, and a HP Z800 Dual Quad Core 2.93 GHz PC)
I do want to make one point clear: This speeds up the import into Avid. You still have to wait for the initial encode to be done. Depending on your encoding software, it could be faster (or slower!), but it DOES free up your Avid to work while the file is encoded elsewhere. Also, the concept of “pay now or pay later” comes into play. Would you rather wait at the front end of a project for the import (less stress), or wait until the END of the project (more stress) – with deadlines – and deal with the transcode / render / mixdown then? Also, think about how the creative edit will be impacted when things don’t play in real-time.
As always, feedback is welcome.