64 lines
2.2 KiB
C++
64 lines
2.2 KiB
C++
// soundgenerator.cxx -- simple sound generation
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//
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// Written by Curtis Olson, started March 2001.
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//
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// Copyright (C) 2001 Curtis L. Olson - http://www.flightgear.org/~curt
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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//
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#include "soundgenerator.hxx"
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#include <simgear/constants.h>
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FGSoundGenerator::~FGSoundGenerator()
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{
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}
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// Make a tone of specified freq and total_len with trans_len ramp in
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// and out and only the first len bytes with sound, the rest with
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// silence
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void FGSoundGenerator::make_tone( unsigned char *buf, int freq,
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int len, int total_len, int trans_len )
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{
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int i, j;
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for ( i = 0; i < trans_len; ++i ) {
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float level = ( sin( (double) i * SGD_2PI / (BYTES_PER_SECOND / freq) ) )
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* ((double)i / trans_len) / 2.0 + 0.5;
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/* Convert to unsigned byte */
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buf[ i ] = (unsigned char) ( level * 255.0 ) ;
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}
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for ( i = trans_len; i < len - trans_len; ++i ) {
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float level = ( sin( (double) i * SGD_2PI / (BYTES_PER_SECOND / freq) ) )
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/ 2.0 + 0.5;
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/* Convert to unsigned byte */
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buf[ i ] = (unsigned char) ( level * 255.0 ) ;
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}
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j = trans_len;
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for ( i = len - trans_len; i < len; ++i ) {
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float level = ( sin( (double) i * SGD_2PI / (BYTES_PER_SECOND / freq) ) )
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* ((double)j / trans_len) / 2.0 + 0.5;
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--j;
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/* Convert to unsigned byte */
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buf[ i ] = (unsigned char) ( level * 255.0 ) ;
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}
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for ( i = len; i < total_len; ++i ) {
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buf[ i ] = (unsigned char) ( 0.5 * 255.0 ) ;
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}
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}
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