samer@3: % framedata - return abstract data object for buffering signal frames
samer@0: %
samer@0: % framedata :: 
samer@3: % 	( s:seq [C,T] 	~'C-channel signal of length T',
samer@0: %	  N:natural 	~'frame size',
samer@0: %	  M:natural 	~'hop size',
samer@0: %	  L:natural 	~'frames per buffer' | ([] => whole file) 
samer@0: %	  options... )
samer@3: %	-> seq [N,L]. 
samer@0: %
samer@0: % Options:
samer@0: % 	wrap/0     if 1, then buffer samples as if one continuous circular signal
samer@0: % 	            otherwise, don't return buffers that wrap round from end to start
samer@0: % 	random/0:   if [], return buffers sequentially, if number or random state
samer@0: % 	            vector, return buffers in random order, using value as seed. 
samer@0: %  filter/[]  optional filter function to apply to long windows before buffering
samer@0: %
samer@0: % Note: if the signal is a multichannel signal, ie of size CxT with C>1,
samer@0: % the samples for each channel are interleaved.
samer@0: 
samer@3: function a=framedata(signal,frame,hop,width,varargin)
samer@0: 	if nargin<4, width = []; end
samer@37: 	opts=options('wrap',0,'random',[],'dim',2,'filter',@id,varargin{:});
samer@0: 	if isempty(width), opts.truncate=0; end 
samer@0: 	
samer@0: 	[span,jump]=windowparams(size(signal),frame,hop,width,opts);
samer@0: 	if isempty(opts.random),
samer@42: 		wd=window(signal,span,jump,'wrap',opts.wrap,'dim',opts.dim);
samer@0: 	else
samer@0: 		wd=rndwindow(signal,span,opts.dim);
samer@0: 	end
samer@0: 
samer@3: 	wd=opts.filter(wd);
samer@3: 	if size(wd,1)>1, wd=map(@flatten,wd); end
samer@3: 	olap=frame-hop;
samer@3: 	if hop<frame, buffn=@(x)buffer(x,frame,olap,'nodelay');
samer@3: 	else buffn=@(x)buffer(x,frame,olap); 
samer@3: 	end
samer@0: 
samer@0: 	% NB: makes sense to cache large windows to save repeated calls
samer@0: 	% extract current large window from data source while processing
samer@0: 	% the buffered window.
samer@3: 	a=map(buffn,cache(wd));
samer@3: end