Transcoding between HEVC streamed input to H.264 streamed output in Core

Overview

Core allows real-time transcoding between an HEVC / H.265 input stream to an H.264 / AVC output stream.

This allows an HEVC stream from an encoder to be converted and delivered to hardware decoders or clients which only accept H.264 streams, or the use of streaming protocols which only support H.264.

The RTMP streaming protocol is not compatible with HEVC, but the MPEG-TS protocol and SRT protocols both support the HEVC codec in addition to the older H.264 codec.

NOTE: if transcoding is not activated, the incoming HEVC stream from the encoder will be left at HEVC by the Sputnik server and will not be converted to H.264. This means that both the outbound streams sent from a Core-controlled Sputnik must be capable of supporting the HEVC codec, and the destination must also be capable of receiving HEVC. 

Transcoder Settings

At this time, there are no configurable settings for the transcoder and all settings are determined automatically.

The transcoded video output resolution, key frame interval, and video frame rate will match the input.

The transcoded video bitrate is based on the video resolution (height and width), encoded frame rate, and encoded key frame interval of the input, based on this formula:

29*w*h*(1+(g-1)*0.2)/g

Substitute w and h for width and height in pixels, and g for the key frame interval (GOP size) in frames. For example, if your encoded video frame rate is 60 and your key frame interval is 2 seconds, the GOP size is 120 (60*2). For 30 fps and 2 seconds, the GOP size is 60 (30*2).

For convenience, online calculations can be done using Wolfram Alpha (clickable link).

These transcoder settings apply for both the VidiU Go and the 700 series encoders.