AWS for M&E Blog
Optimizing Encodes for Picture Quality with AWS Elemental MediaLive
Being able to provide high-quality encoding for a variety of content types can be a challenge. We’re providing a recommended baseline configuration that can be used with AWS Elemental MediaLive to deliver broadcast-grade video quality (VQ) output for all content types. We’ll also illuminate insights into the impact of varying encoding parameters so you can make your own further optimizations to VQ.
When encoding video, the primary parameters that will influence video quality are the choice of the video codec, bitrate, resolution and framerate. They will vary depending on your application and the type of delivery network that is being used. For example, for an IPTV style of delivery over managed networks to set top boxes (IP based receiver/decoder), only a single encode and output is required with a fixed resolution and framerate to a specific set of target devices. This allows tight optimization of the encode based on the output from the target set top box.
For an over the top (OTT) delivery over unmanaged networks (internet), to a wide variety of devices the video will need to be encoded into an adaptive bitrate (ABR) ladder of encodes, which are then packaged for delivery. For each of the encodes in the ladder the resolution, bitrate, and framerate of the encode may be varied. The construction of the ABR ladder of encodes and bitrates should consider the target devices, display size and performance of the network delivering content to the device.
For devices in a home environment, with wired internet access, you may expect to be able to reach and remain at the higher rates. Whereas a mobile device travelling may need to adapt frequently in response to changes in the speed of the available network connection.
AWS Elemental MediaLive is a broadcast-grade live video processing service that creates high-quality streams for delivery to broadcast TVs and internet-connected devices. It continues to evolve to improve video quality and extend support of new codecs and features. Today it supports live encoding using MPEG-2, AVC, HEVC, AV1, up to 4 K resolution, SDR/HDR colour space and 8/10 bit 4:2:0 or 4:2:2 video. MediaLive uses advanced techniques including artificial intelligence models in order to select the optimal encoding toolsets for the content being encoded.
When key parameters of codec, resolution, bitrate and framerate have been set for encoding the next step is to look at how we can optimize the encoding parameters to obtain a high quality encode within defined constraints.
The following table provides a recommended baseline configuration for use with MediaLive which should provide broadcast-grade picture quality for a wide variety of content types. The table provides the navigation path to reach needed parameters, and the notes provide a brief view of the impact of each parameter.
The settings we suggest in the table apply equally for AVC, HEVC codecs (as they are mostly adapted), as well as the SDR and HDR colour spaces unless noted otherwise. If the encode is for a specific type of content (for example, movies, sport, animation, eSports, and user generated content) or to reach other goals (such as minimising encoding latency) there are further optimizations that could be considered in the detailed analysis. This analyses key encoding parameters of the encode allowing you to more tightly optimize the encoding for specific content types.
Conclusion
This blog provides a baseline encoding configuration which can be used to give the best possible VQ for all content types. We have explained the impact of these settings, and for those wanting to optimize tightly for specific content types and applications the detailed analysis provides further insight.
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