Which is the best video authoring(or converting) software?

1)I am new to dvd authoring and wanted to know the best software to author and convert my video files to better formats.

2)If i want to reduce the size of the video, to which format should and what settings should i convert it to get the the best quality on the least size.

3)To which format and to what settings should i convert the video to get the best quality. size is no problem.

4)Can i also improve the audio(or music) quality for example change it to, say, 5.1 channel? if yes, which software is the best to do so?

The main purpose behind all this is that i got GBs of episodes, movies and music from my friend. The episodes are like 700 MB(usually of 41 mins). I wanted to reduce their size to burn them to DVD. so i want a software to do this. the movies are also around 700MB but i wanted to get better quality. so i need a software to do this so i can only watch it in better quality but burn it as it is.

Basically a good converter would do the work. also if anyone can explain me about codecs it would be great.

 

You will have to re-encode and take a quality hit.

Ain't gonna happen.

No.

 

so i would say that your 700mg movie files are avi right? convertxtodvd is your best bet for that, and for music there are some for that, but not sure for thoses, you might try using google for that