Roku Developer Program

[filmgeek]

The encoding guide states:

The dimensions vary on a title-by-title basis depending on the source material and the target aspect ratio for the encoding (e.g. 4:3 or 16:9). Content should always be encoded at full width and the height is adjusted. For example, a 1.66 aspect ratio source is encoded as a 720x432 video and displayed as letterboxed for a 4:3 display.

So this is a bit confusing, because HD is always 16:9. The picture area of a 4:3 film in a 1080p frame would be 1440x1080.

If we have a 2k film that's 4:3 (2048x1540), we should encode at 1440x1080, correct? That would scale down to fit a 4:3 screen, and it will drop into the center of a pillarboxed 1920x1080 HD frame with no scaling.

Thanks!

[TheEndless]

The example in the encoding guide is a bad one, as it's a 15:9 video, in which case you would want to scale to the horizontal resolution. If you scaled to the full width of your particular content, you'd end up with 1920x1444, which would result in wasted bandwidth usage delivering an extra 364 lines of resolution, and would ultimately result in lower picture quality, because the Roku would have to scale it down. I think the general rule of thumb, in the case of 16:9 and 4:3 content, would always be to scale to the native vertical resolution.

[filmgeek]

In the example, 1.66:1 films would be letterboxed on 4:3 screens. But that aspect ratio needs to be pillarboxed on 16:9 screens to maintain the correct shape. I agree that this is poorly written, because it only seems to take into account one of the two possible scenarios for aspect ratios that are not natively 4:3 or 16:9 (we deal with lots of them daily, because we do a lot of film-originated work, so 1.85:1, 1.66:1, 2.35:1, etc.

I guess what it's saying is that if you're going to make both SD and HD streams available and you have a non-video aspect ratio (say, 1.66:1), you'd make two files:

SD at 720x432 (this will be letterboxed by the player to fit a 4:3 screen)
HD at 1800x1080 (this will be pillarboxed by the player to fit a 16:9 screen)

Or in the case of my question, where the source is a 2k 4:3 film scan:

SD at 720x480 (this will be full frame on a 4:3 screen)
HD at 1440x1080 (this will be pillarboxed by the player to fit a 16:9 screen)

Is that how it works?

Thanks!

[TheEndless]

"filmgeek" wrote:
Is that how it works?

I think so. The key is to keep the aspect ratio native to the video, not the screen resolution (i.e., don't encode letter/pillar boxing into the video). Technically, the Roku could probably play your 2k film correctly without you scaling it first, but you'd be wasting a lot of unnecessary bandwidth (and probably overworking the Roku's decoder/scaler).

[filmgeek]

Cool. thanks - that's what I figured it'd be. So, 1440x1080 it is!