Table of Contents
Overview
Wurl's cloud solution enables the delivery of adaptive bitrate HLS linear streams. This distribution workflow utilizes multiple distribution networks, multiple cloud services and ad servers in parallel.
This document describes the HLS formats delivered by Wurl’s platform to Streamers.
HLS Linear Streams
Wurl delivers adaptive bitrate HLS 24/7 linear streams to Streamers.
HLS Linear Description
- Creation of HLS linear streams is based on scheduled lineups created by Content Companies
- Streams run continuously to support 24/7 linear playout
- An HLS stream delivers up to 5 renditions, HD and SD resolutions
- HLS streams carry H.264 video and AAC audio
- Closed Captions are support within an HLS stream, in WebVTT and/or Embedded 608 formats. The presence of Captions is contingent on Content Companies providing caption files to Wurl
HLS Renditions
Wurl requires Content Companies to deliver input video at a minimum resolution of 1920x1080 to ensure the below video renditions can be provided.
Rendition Variances May Occur
Wurl Restream Channels are linear streams that do not originate with Wurl but utilize Wurl’s CDN delivery. Because Wurl Restreaming Channels do not originate with Wurl, the stream specifications are more variable than Wurl-originated HLS Playout Channels.
- For example, Framerate will be normalized to 30 for most content, however, in some cases assets within a stream may not be set to 30.
- Wurl streams are also VBR (Variable Bitrate) rather than CBR (Constant Bitrate). Minor variance should be expected in the Bitrates described above.
Wurl originated Channels (Playout), Content and Ad Slate Audio is normalized to -24db LKFS. For Wurl’s Restream Channels:
- Where Wurl restreams an MPEG-TS source, all audio is normalized to -24db LKFS
- Where Wurl restreams an HLS stream, audio is not normalized. In case of irregularities, the Content Companies must address at the origin
Closed Captions
Wurl provides valid Closed Captions for assets when required, assuming the source file received by Wurl from the Content Company carries valid data.
- Closed Caption Formats: 608 and webVTT
- Single Track Captions Only
- No Live Caption support