So I have downloaded subler to change .264 files that are MKV to MP4. It works great most of the time, very fast etc. The only problem is the inconsistancy. I have some files that work fine on the 4.1 profile. Some of them return an error saying they canot sync to my ipad as it will not be playable. If I change the profile to 3.1, some files will now work. Then there's other files that won't work on any profile. What is up with the variation in what's fully convertable and what's not? I've read that some people use something called MKVtools. Is this better than subler?