Some mostly random discussion and workflow-oriented thoughts on using a mastering codec…
Traditionally (can there be much tradition here yet?), this would be used in a DI process when not going out to film. This is becoming quite common now as theater deliveries are becoming increasingly digital. You want something that hits film’s final resolution of approximately 1.5K and does that very well without being hugely taxing on space and processing power. Currently Cineform and DNxHD are the only codecs I know if being used in this process (caveat: I don’t work in Hollywoodland, this is only from what I read and hear about others doing).
Now, what about the rest of us indie types not going to film but to web, DVD and Blu-Ray? First of all, notice those three (only?) mediums. They’re delivery formats. Each has a different compression, codec, and bitrate. A master is a file you build your delivery formats from. But why not just make your delivery formats from the timeline you ask?
Speed
Let’s look at After Effects for our answer as it provides probably the easiest to understand example. When you render out a composition, you have the option of rendering to as many formats as you have on your system. If you were to duplicate that render to a different format each time, After Effects would render your composition each time. But there’s another option, an option to add a different output format under a single render instance. Add 15 different output formats here and After Effects will render only once. That saves a huge chunk of time!
Using a mastering codec for your finished movie out of the timeline utilizes the same concept: compile and render everything once and build different formats from there. Just for a test (and it’s never had a different result for me) take a timeline and render it twice to different formats. Then take the same timeline render it to your mastering codec and then build the other render from that. It WILL be faster.
Quality
I once built (since it was faster) a h.264 for the web from a blu-ray mpeg stream file. The result blew me away. I rendered the same h.246 file (same specs) from the timeline as a test and it didn’t look half as amazing. My friend was like, “of course.” Like it was something everyone knew.
One of the responsibilities of any film finisher (online editor) or filmmaker (if you’re the one man show) is to make sure that the final piece be it for the web, DVD, or wherever meets the proper technical requirements but looks as good as possible at the same time. Indeed, in the short two and half years doing this, I’ve always had the best looking file by going from the timeline to Cineform first.
An additional benefit, like speed, is when needing to go to multiple formats (as I do), you’re guaranteed a faster transcode/re-wrap, with a file you know has no errors in it and is the best-looking one you can get. And if something does arise, you can make changes to your delivery format much quicker with confidence knowing where the problem lies.
Longevity
Technology is changing and will continue to change rapidly. You’re single H.264, flv, or MPEG4 stream may not be able to play in 5-10 years. And what if you have to come back to that file to make a new copy for a new format? What if you can’t keep the project, but need to keep that master and want to maintain the highest level for future use? By always going to a master codec, you know that if you need anything in the future, you’re not going to be making one copy from another copy. And you always have the best quality file on hand for years to come.
Codecs
I won’t say certain codecs are the only mastering codecs out there, uncompressed is probably ideal, but impractical. So good compression, very high quality, full color space, platform agnostic and half-way decent on space are probably the main considerations. In this camp, I’m in favor of Cineform, and Avid’s DNxHD (probably in that order too). And you might have something else you’re okay with to use as master codec.
Edit: Like HuffYUV on Windows which I was just informed is a popular mastering codec, ProRes is Apple specific which means it doesn’t quite make my cut for a good master codec even though technically probably par with Cineform and Avid.
So give your thoughts if you have ‘em. This isn’t rule-of-law by any means…
Wikipedia Links on Codecs:
Cineform
Avid DNxHD
ProRes 444
Company Information on their Codecs:
Cineform
Avid DNxHD
ProRes 444
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