Today, AWS Elemental MediaConvert adds support for several new features, including improved video quality with single- and multi-pass HQ (High Quality) encoding for H.264 (AVC), expanded Accelerated Transcoding capabilities, and the On Demand profile for DASH output groups.

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/10/announcing-new-aws-elemental-mediaconvert-features-for-accelerated-transcoding-dash-and-avc-video-quality/