Add features related to AudioBooks

[tesshucom]

Consideration for adding audiobook-related features. Related airsonic/airsonic#558, #1761, #352.
Prerequisites: #1885, v111.6.0

According to the UPnP specification, audioBook is a kind of audioItem parallel to musicTrack and audioBroadcast. Therefore, it is considered to be a universal and general requirement to some extent. (Though it should be noted that the realistic priority for this server is lower than musicTrack.)

UPnP models and views are loosely coupled, making them relatively easy to implement. It seems that one of the correct answers is to implement UPnP before the Web page. (If it is only this feature, it is possible to provide relatively early)

Below is our current view on the request.

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• seperate tab (like podcasts) for audiobooks
  • Tabs and menu items of top level vary by app. Like podcasts, we think it's not unnatural for AudioBooks to be the top item. However, it should be optional.
• searchable (book and author as categories[either in its tab or with the library as a whole])
  • The details need to be worked out, but it's not difficult. It is a specification since Subsonic. Need to change specification or add the search criteria for this. Because the search from the current web page excludes AudioBooks by Mediatype.
  • Jpsonic's UPnP search, on the other hand, follows the client application's criteria, unlike web search. (i.e. already supported)
    • Note, however, that this does not necessarily mean that AudioBooks are searchable.
    • Jpsonic's UPnP search follows client requests. For example, an app without video controls will not include videos in searches. There are apps that search for the entire audioItem, and there are apps that search for musicTrack, audioBroadcast, audioBook, etc. separately, or any of them. No specification changes will be made for this. Because it's a search for client apps to request data that's appropriate for their app's functionality.
      • Some apps display everything in a list, while others sort the search results into folders by MediaType or sort them by tags.
    • There are relatively many apps that search for the entire audioItem, but there are some apps that limit it to Music. You may want to evaluate some UPnP apps and choose the one that is easy to use.

• ability to set a folder in settings or base audiobook detection on tags (may be less reliable)

  • Jpsonic does not change or add to this specification. (or already existed)
    • Subsonic/Airsonic specs are like this : Contains audiobook or audio book in path or Genre tag.
    • These are converted to attributes Mediafile#MediaType and used for search filters and the like.
    • The reason Subsonic has such an implementation specification is that ID3 tags dedicated to music do not have tags that indicate media classification. (There is a tag that indicates the medium. such as DVDs and Blu-rays.) Therefore, in order to enable classification equivalent to UPnP internally, each process determines the type at the time of scanning.
• variable speed listening
  • I think this is another matter. If necessary, it will be implemented in WebPlayer, but it's not available from Rest or UPnP, so it's a somewhat narrow request.