Soft forced subs in MP4

[Casco]

Hi,

My aim is to convert my DVD collection to a library of self contained MP4 files, using the X264 and AAC codecs.

I would like to use forced soft subs for those movies which contain foreign language sections, and would like to keep the MP4 files standards compliant. I beleive that the MP4 standard for subtitles is 3GPP, and have found it straightforward to convert subs to this format and mux them into the MP4.

However, I am still struggling to find a way to mark a subtitle track as forced. It is easy to mark a subtitle track as forced in an MKV container, but I cannot see how to acheive the same thing in MP4. Can anyone advise me? Is this even supported, and if so, how to do it?

TIA

[Ritsuka]

In a normal world it would be enough to just have an enabled text track.
But every player got its own way of handling tracks in mp4. So, the answer is "who knows".

[TheSkiller]

Since you always want to have these forced subs enabled and, as Ritsuka said, WILL run into problems when using MP4 for this, why not do it the easy and most compatible way possible: hardsub them into the video.
All you need to do is rip them to a *.SUB and a *.IDX file and then "draw" them into the video with VobSub("Path to sub and idx"). You don't even need to OCR this way.

[Casco]

Thanks for the replies. I've looked at the other possibilities, including hardsubbing, external subs, and other containers. But I'm just trying to ascertain whether there is a standard way of achieving forced soft subs in mp4, regardless of the quirks of current players.

I have seen the "enabled" flag for tracks in MP4s - is that designed to determine the default tracks to be played?