I export my animations as .avi ! Because this give the best colours and the quality is really good. Then I open the file on Adobe After Effects and add some audio. I also export it as .avi but then it has lost a lot of quality. What can i do that the quality stays good?
So according to what you say the lost of quality of your video is not because of AS but After effects, mm.... i dont really know after effects so i hope somebody can help you.
By the way your english is not bad.
I recommend you to use quicktime's mov. Quality and compression are better than avi.
Try with mov "png" instead avi.
You must have in mind too that there are several types of .avi (just like several types of .mov). It's not a software problem, it's about how each format works.
Maybe you could try exporting as PNG sequence from ASP and from AE, then converting to MOV with millions of colors + in Adobe Media Encoder, which I assume you have since you have AE.