Adding subs to video files problem (huge converted files)

Jul 3, 2013
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I am trying to add subtitles to video files, usually .srt subtitle files added to .mp4 or .mkv files.

Using various software programs such as Aimersoft or Submerge, I am able to convert the files successfully, albeit with this bizarre reservation: even though the .srt files are usually smaller than 100K, the converted .mp4 file can end up being anything from 50% to 400% larger than the original video file. In one case, a 1.4GB video file, when added to a 45K .srt file, ended up converted to 6.8GB!

This makes no apparent sense. Worse, when I contact the service departments of the software developers, they can offer no solution and appear baffled as to the cause. I have no idea whether my case is unusual, or whether this effect is the norm. Any help, comment or suggestion would be very welcome.

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