Analog Devices VISUALDSP++ 3.5 Manual page 513

The twiddle table is passed in the argument
¾ twiddle factors. The function
n
tialize the array. If the twiddle table contains more factors than needed for
a particular call on
appropriately; otherwise it should be one.
The argument
output to avoid overflow. If no scaling is selected by setting
to zero, then the input signal should be sufficiently conditioned to avoid
overflow. The
The function will perform static scaling if
static scaling, the function will scale intermediate results to prevent over-
flow. The final output will be scaled by
set to .
log2(n)
If
scale_method
Under dynamic scaling, the function will inspect the intermediate results
and will only scale to avoid overflow. Dynamic scaling therefore mini-
mizes loss of precision but at the possible cost of slightly reduced
performance. The
0 (which indicates that no scaling was performed) and
scaling was performed).
Algorithm
See
cfftrad4_fr16
Domain
Input sequence length
VisualDSP++ 3.5 C/C++ Compiler and Library Manual
for ADSP-219x DSPs
rfftrad4_fr16
controls how the function should scale the
scale_method
argument will be set to zero.
block_exponent
is set to 2, then the function will select dynamic scaling.
block_exponent
on page 4-38.
must be a power of four and at least 16.
n
DSP Run-Time Library
, which must contain at least
w
twidfftrad4_fr16
, then the stride factor has to be set
scale_method
, and
1/n block_exponent
argument will be set to a value between
may be used to ini-
scale_method
is set to 1. For
will be
(as if static
log2(n)
4-97