Convert MT2S to MP4

Converting MT2S files directly to MPEG-4 Videos (.mt2s to .mp4 conversion) is not possible, since MT2S is a non-existing format.

Perhaps this is just a typo, and you are actually searching for ways how to convert Blu-ray BDAV Video Files to MPEG-4 Videos. In that case, please refer to the M2TS to MP4 conversion entry.

Simply put, it is impossible to convert MT2S to MP4 directly.
Thus, there is no so-called mt2s to mp4 converter or a free online .mt2s to .mp4 converter to be found.