Oversampling

   Hi!

I've implmeneted some code for per-module oversampling. It
is based on
FIR filters which are designed from a windowed sinc
function.
Oversampling ratios from 2 to 16 are supported.

To test it, I've implemented Bse::Rectify, a plugin which
should -
without oversampling - generate extreme aliasing.

I am attaching the code here, and an example .bse file. When
running the
bse file, use a fft scope to monitor the rectify output,
while playing
with the oversample ratio setting.

Comments are welcome.

   Cu... Stefan
-- 
Stefan Westerfeld, Hamburg/Germany, http://space.twc.de/~stef
an
/* BseNoise - BSE FM Operator		-*-mode: c++;-*-
 * Copyright (C) 2006 Stefan Westerfeld
 *
 * This library is free software; you can redistribute it
and/or
 * modify it under the terms of the GNU Lesser General
Public
 * License as published by the Free Software Foundation;
either
 * version 2 of the License, or (at your option) any later
version.
 *
 * This library is distributed in the hope that it will be
useful,
 * but WITHOUT ANY WARRANTY; without even the implied
warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General
 * Public License along with this library; if not, write to
the
 * Free Software Foundation, Inc., 59 Temple Place, Suite
330,
 * Boston, MA 02111-1307, USA.
 */
#include <bse/bsecxxmodule.idl>

namespace Bse {

class Rectify : Effect {
  Info    authors     = "Stefan Westerfeld";
  Info    license     = _("GNU Lesser General Public
License");
  Info    category    =
_("/Distortion/Rectify");
  Info    blurb       = _("Outputs -1 for signals <
0 and +1 for signals > 0");
  IStream audio_in    = (_("Audio In"),
_("Audio Input"));
  OStream audio_out   = (_("Audio Out"),
_("Audio Output"));

  group _("General") {
    Int   oversample  = (_("Oversampling"),
_("The amount of internal oversampling. If BSE is
running with a rate of 48000 Hz, "
                                              "an
oversampling of 2 means to perform internal computations
with 2*48000 Hz = 96000 Hz. "
					      "\n\n"
					      "Higher oversampling means better quality
(less aliasing), but also more CPU usage."),
			 1, 1, 16, 1, STANDARD) ;
    Bool  bypass      = Bool (_("Bypass
Rectification"), _("Bypasses Rectification (but
still does oversampling"), FALSE, STANDARD);

  };
};
};
; BseProject

(bse-version "0.6.6")

(container-child "BseWaveRepo::Wave-Repository"
  (modification-time "2006-02-17 07:26:13")
  (creation-time "2006-02-17 07:26:13"))
(container-child "BseCSynth::Unnamed"
  (auto-activate #t)
  (modification-time "2006-02-17 07:26:18")
  (creation-time "2006-02-17 07:26:18")
  (container-child
"BseStandardOsc::StandardOsc-1"
    (pulse-mod-perc 0)
    (pulse-width 50)
    (fm-n-octaves 1)
    (exponential-fm #f)
    (fm-perc 0)
    (base-freq 440)
    (wave-form bse-standard-osc-saw-fall)
    (pos-y 1)
    (pos-x -3))
  (container-child "BseAmplifier::Amplifier-1"
    (master-volume 1)
    (base-level 2.7000000000000011)
    (ostrength 100)
    (ctrl-exp #f)
    (ctrl-mul #t)
    (clevel2 100)
    (clevel1 100)
    (alevel2 100)
    (alevel1 100)
    (pos-y 1)
    (pos-x 1)
    (source-input "audio-in1" (link 1
"Rectify-1") "audio-out"))
  (container-child "BseRectify::Rectify-1"
    (oversample 1)
    (pos-y 1)
    (pos-x -1)
    (source-input "audio-in" (link 1
"StandardOsc-1") "audio-out"))
  (container-child "BsePcmOutput::PcmOutput-1"
    (pos-y 1.03)
    (pos-x 3.15)
    (source-input "left-audio-in" (link 1
"Amplifier-1") "audio-out")
    (source-input "right-audio-in" (link 1
"Amplifier-1") "audio-out")))
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Oversampling

Thread: Oversampling