>
> Robert Hegemann wrote:
>
> > Thank you Ross for the info about radio frequencies.
> > Coding FM quality with sharp cutoff would look like:
> >
> > lame --highpass 0.05 --highpass-width 0
> > ...etc
>
> May I make a case for --highpass 0.016 ? FM Radio usually goes down a bit
> lower than 50Hz. The lowest note on a conventional piano is 27.5Hz, the
> orchestral `double-bass' plays down to 32.7Hz, and a 32-foot organ pipe,
> playing the lowest note on the pedal board, is 16.35Hz, though not many home
> systems will reproduce this except to annoy the neighbours.
>
Just a note on the highpass filter: at 44.1khz sampling rate,
we only have 576 MDCT coefficients on which the filter acts and thus
a frequency resolution of only 22050/576 = 38Hz. So the accuracy of the first
few coefficients is questionable, and a highpass filter at 50Hz would
only effect the first 2 MDCT coefficients. I dont know how big a problem
this is, but a true 50Hz filter would need to be done before
calling lame, using a much larger fft/mdct window.
Mark
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