iPhone Videos app only offer a single subtitle track I rip my Blu-Rays and DVDs, convert to M4V with Handbrake, and create SRT subtitles through OCR, which I then mux into the M4V with Subler (which translates them to "Text 3GPP").

If I ever place more than one subtitle track (foreign-language-only tracks vs. full SDH tracks, or even commentary subtitles, for example), I can access all subtitle tracks on my Mac with iTunes, and also on my Apple TV.

On my iPhone, though, I can only access the first subtitle track.  If there are multiple audio tracks, those are available to me, but on a video that I can confirm has multiple subtitle tracks, the Videos app only shows me the first one.  The others aren't even options.

Is there some trick to encoding or muxing? Or does the Videos app on iOS only support a single subtitle track?
It seems like, as far as I can tell, that the Videos app on iOS only support one subtitle per language. 

I had two English subtitles that both showed up on my Apple TV (as "English") but only one of them in the Videos app. My workaround was to change the language of one of these subtitles to something other than English using Subler (I chose "Unknown"). Then they both showed up i the Videos app as different subtitles.