Add note about the importance of adding the "duration" property to readingOrder items

[larscwallin]

For streaming audiobook applications it is somewhat problematic that the duration property of the readingOrder items is not mandatory.

When resolving a location within the audiobook using a temporal media fragment the user agent will need to first iterate through the readingOrder items in order to determine which item contains the desired location. This is done using the values in the respective duration properties. If this data does not exist it will be neccessary to download all audio files up to a certain point in order to correctly calculate the requested position. This will of course be a major issue, especially in emerging markets where download speeds effectively prohibits this behaviour.

I suggest the addition of a note, or even better a SHOULD, to the section in the spec that describes this property.

[iherman]

Lars, I will move this issue to the audiobook spec's repo.

[iherman]

Oops, sorry, I misread; that is the right repo. Apologies for the noise.

@larscwallin is this something you consider a bug, ie, should be listed as an Erratum, or is it more a feature request? I guess the latter, but I wanted to be sure...

[llemeurfr]

Note that for the reason invoked by Lars, the Audiobook profile of the Readium Web Publication Manifest makes duration mandatory.
ref: https://github.com/readium/webpub-manifest/blob/master/profiles/audiobook.md#2-listing-audio-resources

[iherman]

This issue was discussed in a meeting.

• RESOLVED: In the audiobooks document, elevate the requirement for reading order item level duration to a MUST.

View the transcript

Add note about the importance of adding the “duration” property to readingOrder items (issue audiobooks#108)
See github issue audiobooks#108.
Lars Wallin: We want the sum of the audio files to be equal to the entire audio book..
… this is needed to support streaming. We don’t want to download everything to get this information..
… You need to easily determine where you want to go in the entire book..
Laurent Le Meur: A reading system must be able to jump to a specific location in a specific track, when the user opens an audiobook and wants to start from the position he has left during a previous session. For that the duration of an item in the reading order must be mandatory..
Proposed resolution: In the audiobooks document, elevate the requirement for reading order item level duration to a MUST. (Wendy Reid)
Wendy Reid: +1.
Ivan Herman: +1.
George Kerscher: +1.
Laurent Le Meur: +1.
Resolution #2: In the audiobooks document, elevate the requirement for reading order item level duration to a MUST.
Wendy Reid: will make change in editorial spec..
Lars Wallin: @BigBlueHat I plan to bring up some web annotations a little later, if there is time, just so you know ;).
Ivan Herman: The two enhancements are fairly significant and we should check with Tzviya and Matt if we should republish the spec. This requires testing..
… We need to make it highly visible to implementers..
Wendy Reid: This came from implementors and we need to find a way to get it in front of implementors..
Ivan Herman: Also, we have to be careful about editing the text: the differences in the editors spec have to be tracked. It is not the normal editing, and more needs to be done to track changes..