Not possible to rewind to previous mp3 files on iOS

[AndreasLymalmMTM]

Problem

When playing a publication (WebPubAudioOnly format), doing a rewind (previous()) only rewinds to, at most, the start of the current mp3 file.

Expected Result

Should rewind to previous mp3 file the remaing seek interval, like it does on Android.

[ddfreiling]

This is due to an implementation difference between kotlin-toolkit and swift-toolkit.

Android side has a SmartSeeker, iOS side does not seem to have the same. I suggest implementing SmartSeeker in swift-toolkit, if this feature is a priority.

See
https://github.com/readium/kotlin-toolkit/blob/develop/readium/adapters/exoplayer/audio/src/main/java/org/readium/adapter/exoplayer/audio/SmartSeeker.kt

https://github.com/readium/swift-toolkit/blob/develop/Sources/Navigator/Audiobook/AudioNavigator.swift#L239-L241