Getting ready to create HLS rendition groups

Step 1. Create a mapping

Identify the video, audio, audio rendition groups and captions you require. Review the Rules for rendition groups to ensure you design an output that is valid. For example:

• Video “high definition.”

• Video “low definition.”

• A rendition group named “AAC group” for AAC audio.

• A rendition group named “Dolby group” for Dolby Digital audio.

• Audio English AAC in “AAC group” rendition group.

• Audio English Dolby Digital in “Dolby group” rendition group.

• Audio French AAC in “AAC group” rendition group.

• Audio French Dolby Digital in “Dolby group” rendition group.

• Video “high definition” to be associated with both rendition groups.

• Video “low definition” to be associated with the “Dolby group” rendition group.

• Captions in English and French in WebVTT format, to be associated with both rendition groups.

Step 2. Determine defaults and auto-selection behavior

For each audio rendition group, decide which audio will be the default and how auto-selection works for the non-defaults. Setting up this information is useful if:

• The user has specified an audio preference on the client player but that preference is not available, or

• If the user has not specified an audio preference.

(Obviously, if the user has specified a preference and that preference is available, the client player will select that preference.)

Determine defaults and auto-selection behavior

Set the Audio Track Type field. The options for this field for each audio stream follow.

Value	Client player behavior	Representation in HLS manifest
Alternate Audio, Auto Select, Default	The client player should select this stream. Only one stream in the rendition group should be set as the default; otherwise, the client player may behave unexpectedly.	EXT-X-MEDIA with DEFAULT=YES, AUTOSELECT=YES
Alternate Audio, Auto Select, Not Default	The client player may select this stream. Any number of streams in the rendition group can be set this way.	EXT-X-MEDIA with DEFAULT=NO, AUTOSELECT=YES
Alternate Audio, not Auto Select	The client player should never select this stream. Any number of streams in the rendition group can be set this way.	EXT-X-MEDIA with DEFAULT=NO, AUTOSELECT=NO
Audio-Only Variant Stream	The client can play back this audio-only stream instead of video in low-bandwidth scenarios.	EXT-X-STREAM-INF

1. Set the Alternate Audio Track Selection as follows:

   Desired result	How to set
   There is a default. The player can auto-select any of the other audios.	Set only one audio stream to “Alternate Audio, Auto-Select, Not Default, Default.” Set every other audio stream to “Alternate Audio, Auto-Select, Not Default.”
   There is a default. The player cannot auto-select any of the other audios.	Set only one audio stream to “Alternate Audio, Auto-Select, Not Default, Default.” Set every other audio stream to “Alternate Audio, not Auto-Select.”
   There is a default. There are specific audios that the player can auto-select.	Set only one audio stream to “Alternate Audio, Auto-Select, Not Default, Default.” Set some of the other audio streams to “Alternate Audio, Auto-Select, Not Default.” Set some of the other audio streams to “Alternate Audio, not Auto Select.”
   There is no default. The player can auto-select any audio it chooses.	Set every audio stream to “Alternate Audio, Auto-Select, Not Default.”
   There is no default. The player cannot auto-select any audio.	Set every audio stream to “Alternate Audio, not Auto-Select.”
   There is no default. There are specific audios that the player can auto-select.	Set some audio streams to “Alternate Audio, Auto-Select, Not Default.” Set some audio streams to “Alternate Audio, not Auto-Select.”

2. In addition, if you have an audio that is intended as the audio to play when the bandwidth is so low that the video cannot be delivered, then set that audio to “Audio-Only Variant Stream.”