Bit rate from --aactomp3

[RS]

Some podcasts, such as Moneybox, are at 48kbit/s .  It is adequate for mono
speech programmes, especially if it is to be listened to on a cheap mp3 
player
while walking.  Once it has been compressed to 48kbit/s, any higher 
frequency
information is gone.  It cannot be retrieved by converting at a higher bit 
rate.
Also the conversion to .mp3 at 128kbit/s takes a lot longer than the
--radiomode flashaaclow .m4a download at 48kbit/s.

It is difficult to see what parameters get_iplayer passes to ffmpeg.  As far 
as I have
been aware, when tv programmes are converted (by default) from .flv to .mp4,
the .mp4 bit rate is similar to the .flv bit rate.

This is the first time I have used get_iplayer for a radio programme, so I 
cannot
say whether the increase of bit rate in --aactomp3 is a new problem.