Want to apply fading effect to audio, do I have to recompress?

[Chainmax]

I am trying to make a DVD out of a multitude of videos taken by a camera. Since they all represent very different scenes, I want to make fading effects to the video and audio so when put together they flow in a smoother way. Is there something within Avisynth or VDubMod that will help me avoid recompressing the audio or am I out of luck?