About in-line button controls, you're in luck with Xduoo X3II. When booted in stock firmware mode (Xvortex's custom firmware is dual-boot; you could select between stock FW and Rockbox at start-up), they work (play/pause button, volume controls, and all), both in wired and Bluetooth headsets, whether if they are single-button or the ones with volume controls. The inline controls, along with Bluetooth, don't work in Rockbox mode.
Many thanks for clarifying! This definitely moves the x3ii to the top of my list.
The X3ii manual mentions it supports CTIA standard, but would need an adapter for OMTP standard.
What is less clear for me is how to determine which standard my headset uses.
Is it safe to assume that CTIA is the norm (does not need to be mentioned), and it would be specified if OMTP?
I have JVC HAFR100X, and I have not found specific details about the 1-button control beyond "iphone, smartphone and tablet compatible".
http://www.us.jvc.com/headphones/in_ear/ha_fr100x/
My Forza Metallo Wireless headset is great, but does encounter significant interference in certain parts of my cycling commute (ie streetcar tracks, no walls, moisture, etc).
It worked relatively well with my 7th gen iPod Nano, but was a nightmare with my Benjie T6 (unbearable distortion, huge delay in response time with inline control).
The ultimate win scenario would be if inline control functionality would work through Rockbox, so fingers crossed.
Further Clarification - Is it possible to backup usage data through Android HibyLink Connection?
My hope would be, on occasion while listening, to add songs to specific playlists (ie Instrumental, Live, etc).
When using Hiby, can you produce m3u or m3u8 files (that you could adjust on a computer)?
This was one of the many reasons why Rockbox kicked ass on my T6 - Very easy to add songs to .m3u files that can be backed up or altered on a computer.
It was very easy to add to favorites list on HIby T6, but you could not customize the list name, nor could you export that list.
Lastly - My understanding is that through Xvortex firmware, the max songs is 30000. Is the native firmware capped at 15000?
If you max out at 30000, does it slow down, or does it still work the same?
With my T6, I have more than 15000 songs. With playlists made in Rockbox (and transferred to root), they work in Hiby, but only for songs that were included in 15000 scan.
T6 Hiby playlists accessed through file browser skip songs that were not included in the 15000 limit.