readme.txt

语音信号进行Fir滤波

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README.txt  Guitar Distortion

Analog Devices, Inc.
DSP Division
P.O. Box 9106
Norwood, MA 02062

* DUE TO THE SIZE OF THIS DEMO, IT CANNOT BE REBUILT WITH A DEMO LICENSE,
  ONLY DOWNLOADED AND RUN.  TO REBUILD THIS PROJECT, YOU'LL NEED A 
  FULL LICENSE.  *


This program demonstrates one technique for distorting a signal similar to a
tube-amplifier.

The incoming signal is sent through a first clipped on both the positive and
negative side by 2 independant paramters.  After this, the clipped signal is
filtered by 3 parallel IIR biquads and each filtered result is sent though a
delay, mixed together and sent out.


    INPUT               PREFILTER
    GAIN                  GAIN
        |                   |   /--[IIR 1]---[DELAY 1]----\
        |                   |  /                           \
 x[n]o--x--[CLIP by +x, -y]-x-<---[IIR 2]----[DELAY 2]------+------o y[n]
                               \                           /
                                \--[IIR 3]---[DELAY 3]----/

The following parameters can be modifed via the preprocessor variables

Gain
INPUT_GAIN      (4.0)
PREFILTER_GAIN  (2.0)

Clip
POS_CLIP        (0.08)
NEG_CLIP        (-0.08)

Delay Line Length (samples) - each must be less than 1000
DELAY_LINE_0_LEN    (200)
DELAY_LINE_1_LEN    (743)
DELAY_LINE_2_LEN    (431)

DElay Line Feedback
DELAY_LINE_0_FB     (0.4)
DELAY_LINE_1_FB     (-0.7)
DELAY_LINE_2_FB     (-0.3)

Filter center frequency
FILTER_CF_0         (600.0)
FILTER_CF_1         (150.0)
FILTER_CF_2         (300.0)

Filter width
FITLER_WIDTH_0      (150.0)
FITLER_WIDTH_1      (150.0)
FITLER_WIDTH_2      (150.0)

This is one of many techniques to simulate a true tube-amplifier sound.

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