aspectRatio

To better control resolution and aspect ratio of thumbnails, we recommend that you use the values MaxWidth, MaxHeight, SizingPolicy, and PaddingPolicy instead of Resolution and AspectRatio. The two groups of settings are mutually exclusive. Do not use them together.

The aspect ratio of thumbnails. Valid values include:

auto, 1:1, 4:3, 3:2, 16:9

If you specify auto, Elastic Transcoder tries to preserve the aspect ratio of the video in the output file.