Next week, the Loews Hotel here in Hollywood will play host to the SMPTE 2014 Annual Technical Conference & Exhibition, during which we will be taking the stage with Mr. Bruce Devlin to learn how his university professor taught him not to be a “smart-arse” – but also for us both to talk a little bit about frame-rate conversion.
Back when Bruce was at university, the temporal world was pretty simple; TV was interlaced at either 30fps or 25fps, while film was still shot on actual film and was made up of 24 full frame images per second, in other words, progressive 24fps.
Now, it would be inappropriate to comment as to whether the teachings of a certain professor have withstood the tests of time (I’ll leave that for the post-session Q&A), but the world of moving images has certainly graduated to a higher level.
In the 1980s & 90s, most content was viewed in the resolution and frame-rate that it was originated in – converting between frame-rates was an intensive process that relied on racks full of hardware.
Today, the link between content creation and consumption is much less coupled – cameras have selectable shooting modes and rates, editors can mix frame-rate and resolution in a project and even on a single timeline, and OTT distribution is completely frame-rate and resolution agnostic. The in-to-out matrix is therefore significantly more complex.
Where your content comes from, where it’s going and how fast it needs to get there will dictate what transform and technology, or technologies you need to use to perform the conversion. For example, film originated (or filmic) content that has been converted and edited at 30fps, but then needs to be returned to 24fps for web distribution will, in order to get the best result, require a different transform type to TV content, originated at 25fps but distributed at 30. Equally, whether that conversion happens in CPU, GPU or dedicated hardware may well be dictated by your workflow and infrastructure.
So, without listing them, here we are with a matrix of at least 20 different conversions with a minimum of 10 transform types and three technology choices – if you’re dealing with a variety of content, that’s going to give you a few decisions to make. Just to make matters more fun, typical converters have more menu options than this place and, with the industry adopting new frame rates and resolutions, there’s a chance that it could get even more complex.
If you’re going to be attending the SMPTE conference, make sure not to miss our presentation, and how we propose to simplify this problem.