Did you change any encoding

Did you change any encoding settings when you convert the file from mp4 to avi? To maintain the image and audio quality, you need to keep things no change prior to editing, and just transfer the container from .mp4 to .avi.

I tested so many video encoders and Digiber converter http://www.digiber.com is the BEST so far, you can choose to convert the file keep original options, or compress to a smaller size.

For EDITING, Sony Vegas is pretty decent if you’re into making your videos all fancy and stuff