Not a get_iplayer query, but a related question

[Clive]

I run get_iplayer under Linux Mint 11 and it works splendidly well. I 
have been d/l the Proms as m4a files and finding that many of them 
contain acres of the following program. Does there exist a Linux gui 
that will enable me to trim off the excess? I have tried some of the 
Windows applications under Wine but not had any success - they install 
but don't seem to function. One (Free Audio Dub) played the file as 
though it was playing twice, the two a fraction of a second apart. 
Others simply don't install or install but don't recognise m4a format.

I hope this off-topic post does not break any rules.

Thank you.