[linux-audio-user] extract and mix

I couldn't find a way to do this in ecasound, maybe there's a way to do it. Here's what I want to do: Find the exact length of a audio file in ms. I think ecalength can do this, I know it's not sample accurate, but I just need down to the around 1ms. Maybe there's another option other than ecalength. Then, I want to extract a section of another file: at a specific location in ms at a length of the file above. Then, mix that extracted segment with another file and save the result to a new file. How can this be done? I don't know of a utility that can extract a specific length at a specific location in ms. brad