Arny Krueger wrote:

The file already exists. 128kb/s, 44.1k. The question
is how to cut this existing file in half with the least
effect on sound quality. Going from stereo to mono would
constitute a big sacrifice.

IME, not really.

Cutting the upper frequency
response to 10kHz would be much less bothersome.

Most MP3 encoders implement a soft high frequency cutoff as the bitrate goes
down. Dropping the sample rate to 22 KHz is obviously more like a brick
wall.

The perceptual coder doesn't assign the same importance to the octave
between 11 kHz and 22 kHz as it does to the range between 0 Hz and 11 kHz,
anyway, so dropping the sample rate to 22 kHz wouldn't produce the desired
halving of file size.


Francois.