[music-dsp] fast algorithm for seamless joining of two cut waveforms

[Anders Torger]

Say we have a sound signal A and a sound signal B. When A ends, B takes over. 
The problem is that the A waveform can end at any amplitude, and B can also 
start at any amplitude. Thus, there is a great risk that there will be an 
audible clicking sound in the joint.

What I need is an algorithm that modifies the B waveform so it connects 
smoothly to A.

A and B actually comes from the same original signal, but processed with 
convolution with different filters. The goal here is thus to remove the 
potential clicking artifact when filters are changed.

The algorithm must be relatively cheap in terms of processor cycles. The 
algorithm to lengthen A a block into B and then fade out/in and mix will 
probably sound just great, but is too demanding, since in the overlap block 
the convolution must be made with both filters -> twice the processor time 
needed -> realtime performance strongly reduced.

Some sort of simple time-domain solution would be great I think. Any ideas?

/Anders Torger