I'm converting video files to watch on my iPad from .mkv to .mp4 as per the settings in avc. What i'm finding thou is that the original .mkv of 147mb is being converted to .mp4 of size 560mb. Nearly increasing 4 times. Any advice?
MKV and MP4 are container formats. AVC is encoding format. File size does not depend much on container type, although some containers allow for smaller file sizes, like MKV takes less space than TS because metadata is not repeated in the stream.
The single defining parameter of file size is data rate. Depending on the encoding format, frame size and frame rate you should select a reasonable data rate when encoding. Say, 5 Mbit/s for MPEG-2 Part 2 may be too low for HD video, but more than enough if you choose AVC/H.264.
Also, "mb" means "millibits". If you wanted to write "megabytes" you should have capitalized both "m" and "b".