Adding multiple media overlays with EPUB3 ?

[parkellipsen]

Hi,

so, I've recently discovered that the Thorium reader application (and possible others) support media overlays that allow you to synchronize audio narration with the text.

I succesfully managed to assemble an EPUB3 book with an audio narration layer using Sigil.

Now my question is, does the standard allow to add multiple overlays for the same text passage ? The <par> tag allows only a single <audio> tag inside, and nesting <seq> tags in one <par> doesn't work. I neither found a way to add multiple SMIL definitions for the overlays.

I haven't found anything that'd explicitly forbid adding multiple overlays. Can anyone enlighten me whether that's possible within the standard ?

Best,
n

[Doitsu]

I haven't worked with overlays, but, IIRC, you might be able to use the Sigil Icarus plugin for it.

[parkellipsen]

Hmm I read about that plugin, but I wonder whether it is still necessary? I think it stems from a time when Sigil didn't support EPUB3 out-of-the-box?

In fact I tried it and couldn't really make it run, but I was still able to assemble the ebook without it.

[KevinH]

The latest spec only allows 0 or 1 audio elements per par.

See: https://www.w3.org/publishing/epub3/...-smil-par-elem

2.4.6 The par Element

The par element contains media objects which are to be rendered in parallel.

Element Name
par

Usage
One or more par elements MAY occur as children of the body and seq elements.

Attributes
epub:type [optional]
An expression of the structural semantics of the corresponding element in the EPUB Content Document.

The value is a white space separated list of property [Packages32] types. Refer to Semantic Inflection for more information.

id [optional]
The ID [XML] of the element, which MUST be unique within the document scope.

Content Model
In any order:

text [exactly 1]

audio [0 or 1]

The audio element is OPTIONAL only if its sibling text element refers to audio or video media (see Embedded Media), or to textual content intended for rendering via Text-to-Speech (TTS).

Have you thought about creating an epub with multiple renditions? Would that help?

[KevinH]

Based on my limited reading of the spec it states:

It MAY refer to more than one EPUB Content Document, but an EPUB Content Document MUST NOT be referenced by more than one Media Overlay Document

where "It" here is a Media Overlay Document.

So the only way to include multiple media overlays to basically the same xhtml content document would be to duplicate that xhtml document under a new name and associate it with the second media overlay.

Probably better to just split it into two different epubs.

[parkellipsen]

Hmm ok, that's pretty unambiguous ... thanks for helping me interpret