expected end of line but found unknown token - terminal

Question

Ok so after days of searching, here I am. I am new to ffmpeg, applescript, and terminal.
I want to use ffmpeg to batch convert a group of selected files in any folder. I was successful in doing this by opening the terminal at the folder location and using this code:
for f in *.flv; do ffmpeg -i "$f" -acodec libmp3lame -b:a 256k "${f%.flv}.mp3" && rm "$f"; done
which finds all flv files, and converts it to 256 bit rate mp3, then deletes the original files.
Now I want it to be more automated, so I looked into creating a service. I tried running an apple script through automator, which I want it to open the terminal at the folder location the file then run the code to convert the files. Here's the code I attempted:
tell application "Finder" to set currentFolder to target of front Finder window as text
set theWin to currentFolder's POSIX path
tell application "Terminal"
if not (exists window 1) then reopen
activate
do script "cd " & quoted form of theWin & ";clear" in window 1
tell application "Terminal"
do script "for f in *.flv; do ffmpeg -i "$f" -acodec libmp3lame -b:a 256k "${f%.flv}.mp3" && rm "$f"; done"
end tell
end tell
The first part of code opens up terminal at the folder location just fine. But when I add the part with the ffmpeg code it crashes. The error is apparently with the "$", those are what light up as the error, the error message says "Expected end of line, but found unknown token". Looking for some assistance please. I need the "$" because those are what make the loop work for renaming the files and such.

Answer 1

You have to escape the quotes when you pass the string using \"
This line becomes:
do script "for f in *.flv; do ffmpeg -i \"$f\" -acodec libmp3lame -b:a 256k \"${f%.flv}.mp3\" && rm \"$f\"; done"