transcomp~ uses transdetect~ to shape the initial attack and release of a signal.
Requires IEM's FIR~, fexpr~ and dbtorms~ which are provided in PD-Extended.
To work properly the transdetect folder should be added to PD's path.
Start by opening help-transcomp~.pd
01 Implementation:
transdetect~ works by using two pairs of envelope followers. The first pair
subtracts an envelope follower with a slow attack from an accurate follower,
the result of which is a signal containing the initial attack. For the initial
release, the second pair subtracts an accurate envelope follower from one with
a slow release.
An envelope follower measures the mean square power of a signal over time
(see 3.audio.examples/H06.envelope.follower.pd for details on implementing an
envelope follower). To do this we must use a low pass filter at a very low
frequency. In order to achieve an accurate follower a linear phase FIR filter
was used (using IEM's FIR~ external). Unfortunately this introduces a phase
delay.
In order to facilitate the use of different envelope follower implementations,
transdetect~ requires a filter type as a creation argument implemented in
followernameTransDetectEF~.pd. 4 linear phase fir implementations are provided:
181, 251, 451 and 501 taps filters. The 501 taps filter provides the most
accurate filter but with a phase delay of 5.668 ms at 44.1kHz (raise the
sampling rate to lower the phase delay). They were all generating using
http://www.dsptutor.freeuk.com/FIRFilterDesign/FIRFiltDes102.html with a
cutoff frequency between 5 and 10 Hz.
A compromise between accuracy and phase delay might be achieved by using
minimum phase FIR filters. A 5th implementation using PD's native lop~ object
is also provided under the designation iir (FIR~ not required).
Along with different possible envelope follower implementation transdetect~
also requires an attack and hold type implemented in
attacknameTransDetectAttackShape~.pd and holdnameTransDetectHoldShape~.pd
respectively. These implementations dictate the kind of attack and release
curves used on the envelope followers (linear, slow[er|est] and fast[er|est]).
All implementations provided use fexpr~. A more efficient external could be
made to take fexpr~ place.
02 Use
In help-transcomp~.pd patch enable start and pay attention to the snap in the
hit. Disable the green toggle button to disable the compression make the snap
go away. Check out the tables on the left to see the results of the transient
compression.
transcomp~ is useful when used with recorded drums to maximize or minimize
its transient (to make it punchier or to make snare drums less clappy).
transcomp~ uses transdetect~. By itself transdetect~ can be used to synthesis
hits from a recording. For example, take a bass drum recording and use the
signals generated by transdetect~ to shape the frequency and envelope of a
synthesized kick drum.
Would love to have some feedback and some help in turning the linear phase filters into minimum phase filters.
