Hello! I am trying to re-encode MKV files and am getting pretty desperate. FFMPEG changes my files to MP4 format, with the same quality intact, but the file size nearly doubles with every conversion. (I don't know if this is helpful, but using conversion programs like HandBrake yields the same results: same quality but double the size of the original MKV.) This is taking up a lot of GB on my laptop, but I absolutely need the MP4 container to play my videos in Sony Vegas.

Here is the code that I run:

ffmpeg -i input.mkv -c:v libx264 output.mp4

Why is the file size doubling? Is there anything I can do to prevent this or do you have any other suggestions? I seriously appreciate any help, thank you so much!!