samer@32: function edges=as_cqedges(fs,range,res,F0)
samer@32: 
samer@32: % as_cqedges - Audio Spectrum linear to log frequency map (no checking)
samer@32: % 
samer@32: % Converts a constant-Q filterbank specification into a list of band
samer@32: % edges, and optionally the sparse mapping matrix
samer@32: % which can be multiplied by a STFT power spectrogram to get a 
samer@32: % constant-Q spectrogram. 
samer@32: %
samer@32: % as_cqmap0 ::
samer@32: %    real     ~ 'sampling rate',
samer@32: %    [[2]]    ~ 'requested lower and upper cut-off frequencies',
samer@32: %    real     ~ 'resolution in octaves',
samer@32: %    real     ~ 'origin of frequency grid in Hz (defaut=1kHz)'
samer@32: % ->
samer@32: %    [[L-1]]  ~ 'frequency bin edges',
samer@32: %    [[L,M]]  ~ 'L by M sparse array'.
samer@32: 
samer@32: % origin of frequnecy grid defaults to 1kHz
samer@32: if nargin<4, F0=1000; end
samer@32: 
samer@32: % quantise requested edges and represent them in
samer@32: % in units of res on a log frequency scale.
samer@32: limits = round(log2(range/F0)/res);
samer@32: 
samer@32: % convert to normalised frequencies (fs=1)
samer@32: edges = (F0/fs)*2.^(res*(limits(1):limits(2)));
samer@32: 
samer@32: % remove any edges above Nyquist rate
samer@32: if edges(end)>=0.5, edges = edges(edges<0.5); end