Requirements for a read aloud navigator.

[qnga]

As per Mickaël's suggestion, I'll try to list the requirements for a read aloud navigator that I'm aware of, feel free to add something or correct me if I'm wrong.

Terminology

• I call read aloud navigator a component reading the content aloud, without any visual rendition. Requirements for interactions with visual navigators are listed too though.
• I call meaningful fragment of content a guided navigation node, a sentence or a chunk of sentence. Supporting words is not mandatory. In the case of a rendition using some prerecorded content (e.g media overlays), only guided navigation nodes are supported.

Prerecorded content

• Support discontinuities in playback: some chunks of an audio file can be skipped.
• Mix prerecorded content and text to speech.

Voices

• Use different voices for different content parts, up to a different voice for a foreign word.
• Support online voices.
• Change preferred voices at runtime.

Playback modes

• Continuously read the publication content.
• Automatically pause the playback between meaningful fragments of content.
• Set a silence between the playback of meaningful fragments of content. These silences are not taken into account in the content duration.

Playback enhancements

• Add silences in the range of 200ms-2s between nodes depending of their roles. Those silences are taken into account in the content duration.
• Change speed and pitch.

Navigation

• Inspect the content tree and the node roles.
• Jump to a specific node.
• Start from a node matching a given ref, from the beginning of the node or after skipping some text.
• Jump to the previous or next meaningful fragment of content.

Skippability and escapability

• Escape the current node if it's escapable.
• Skip the current node if it's skippable.
• Change the set of escapable and skippable roles at runtime.
• Automatically skip skippable nodes.

Interaction with visual rendering

• Highlight the meaningful fragment currently being played.
• Go to the current playback location in the visual rendition.
• Start playback from some location from the visual rendition.