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When implementing large delay length changes (by many samples), a
useful implementation is to cross-fade from the initial delay
line configuration to the new configuration:
- Computational requirements are doubled during the cross-fade.
- The cross-fade should occur over a time interval
long enough to yield a smooth result.
- The new delay interpolation filter, if any, may be initialized in advance
of the cross-fade, for maximum smoothness. Thus, if the transient
response of the interpolation filter is
samples, the new delay-line
+ interpolation filter can be ``warmed up'' (executed) for
time steps before beginning the cross-fade. If the cross-fade time
is long compared with the interpolation filter duration, ``pre-warming''
is not necessary.
- This is not a true ``morph'' from one delay length to another since we do not pass through the intermediate delay lengths. However, it avoids a potentially undesirable Doppler effect.
- A single delay line can be shared such that the cross-fade
occurs from one read-pointer (plus associated
filtering) to another.
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