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This is a simple overview and a list of different aspect ratios that are 16:9, and some notes on encoding them with H.264.

H.264

The best results for H.264 encoding comes from using 16×16 blocks. This should allow the encoder to do a much better task at encoding. However, you don’t need to. Since you are starting out with a 16:9 resolution (likely 1920×1080 or 1280×720 (ie: 1080p and 720p)), there are not many which provide a width which is divisible by 16.

For my tests, I didn’t actually take this into account, and simply used my original HDV resolution (1440×1080 really, but I wanted to convert it to square pixels) .

In addition, I’ve found very few good encoders for H.264 which are, to me, easy to use. The one I have been using is StaxRip, since it has an excellent walkthrough from start to finish, although contains some issues; it can’t do anamorphic video, which HDV uses. Instead, square pixels are the name of the game. Also, when creating a queue (as internet video is prone to be in at least low and high quality) it sometimes goes odd. The audio encoding part of it also seems a bit unwieldy with very little information being available to change the AAC audio encoding. But it works fine still!

Recommended resolutions

If you are not cropping a 1920×1080 image, then the maximum resolution you’d really want to put on the internet is around 50% of the original, being 960×540. For medium (and very acceptable) size, I chose to half it again to 480×270. Then, for a tiny size, half again is 256×144.

Out of these, only 256×144 is able to make full use of H.264′s 16×16 encoding, but this didn’t worry me. To get the best encoding however, choosing a suitable scale from the tables below with both height and width in italics would be a good idea – then using around half, and around a quarter sizes of this initial resolution to produce lower quality versions.

For a better quality “High” – perhaps for release onto TV sets – scaling down 1920×1080 to 1280×720 (which is 66.67% of the size) is a good idea, and is also able to take advantage of 16×16 encoding. This is 720p scale.

For other resolutions then 16:9, try the aspect ratio calculator to find them.

1920×1080 resolutions

To find a perfect lower resolution here is a list of them. The bolded entries are ones in roughly 10% steps of the original size (so 90%, 80% etc. of the original size). The Italic numbers are divisible by 16, which of course means all the heights are.

1280×720 resolutions

And here is 1280×720 resolutions, with the same key:

Other resolutions

You can calculate whatever resolutions you like on my aspect ratio calculator.