When most users speak of embedding subtitles, it is generally accepted that the subtitle is placed within the same file container as the video and audio and its metadata/subtitle track rather than relying on a seperate subtitle file. (named exactly as the container filename).
Exactly
Anonymous
Sorry, after compiling the files for renojim, I realized that the mp4 file I was using to test had a 608/708 closed captioning track in it so did not show up as a subtitle track. When I imported a subtitle track into it (and thought it was playing), it was actually displaying the 608/708 track that will natively show in RMP. (the whole folder of files I was checking actually had closed captioning tracks).
Basically, I gave you bad info. (I should have double checked my file outside of ffmpeg and it would have alerted me to the track.).
Soft-embedded SRT files will not play in mp4 files on Roku (RMP) natively. (neither will vtt or ass) However, hard-encoded SRT files (burnt-in) will play on the mp4 files on RMP.
As mentioned by renojim above, you can take your mp4 file containing the subtitle and convert it to mkv which will display in RMP. (No lengthy re-encode necessary if using ffmpeg)
ffmpeg -i a.mp4 -c:v copy -c:a copy b.mkv
[where a.mp4 is the name of your orig mp4, and b.mkv is the name of your new mkv]. Literally seconds to complete on most computers.
Another method would be to extract the subtitles and then place them in the same folder as the video file. (using the same name).
Sorry for the bad info above. It really is just the case that there is nothing wrong that you are doing. I had just become so accustomed to importing srt files into my mp4s and changing them to mkv that I didn't remember that the reason I actually use the mkv format was so that the subtitles would display on all my devices and Roku. (and since I almost exclusively watch my library through my Roku, I just automatically use the mkv format).
So closed captioning tracks will display in mp4 on Roku, just not a soft encode. I did test the hard encode of a SRT on a mp4 and that also will display fine in RMP.
I did send some info to renojim so if you want the same files to play around and see the differences and the ffmpeg commands let me know and I will send you a link to them via a PM.
Thank you for your help and work
I have decided to return the Roku stick, the low power required (running off a usb on the tv is what attracted me) the hardware is excellent
The media player seems poor compared to VLC and kodi and others freely available on android tv so it will be another android tv box for me so I need to find one with the uk catch up apps iPlayer ITVX all4 and C5 this is quite limiting google streamer is one but expensive
Anonymous
A few points:
