Bauer stereophonic-to-binaural DSP: library description.
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The bs2b library is simple to use. See tables 1 and 2 for example. It is a reductive code of 'bs2bstream.c'. The 'bs2b.h' and 'bs2bclass.h' files of the source code package can help also.
There is a more complex example available on-line.
Table 1. Example of using of bs2b library (C).
#include <stdio.h>
#include "bs2b.h"
int main()
{
t_bs2bdp bs2bdp;
short sample[ 2 ];
bs2bdp = bs2b_open();
/* Default init value
bs2b_set_srate( bs2bdp, 44100 );
bs2b_set_level( bs2bdp, BS2B_DEFAULT_CLEVEL ); // 700 Hz, 4.5 dB
// or another way
bs2b_set_srate( bs2bdp, 44100 );
bs2b_set_level_fcut( bs2bdp, 700 ); // 700 Hz
bs2b_set_level_feed( bs2bdp, 45 ); // 4.5 dB
*/
/* raw LPCM, signed 16 bit, native to CPU byte order, stereo interleaved */
while( 2 == fread( sample, sizeof( short ), 2, stdin ) )
{
bs2b_cross_feed_s16( bs2bdp, sample, 1 );
fwrite( sample, sizeof( short ), 2, stdout );
}
bs2b_close( bs2bdp );
bs2bdp = 0;
return 0 ;
}
Sample rate default value is 44100 Hz. Crossfeed level default value is 700 Hz, 4.5 dB. If a sample rate of audio data is different or if you want to change crossfeed level then you must call 'bs2b_set_srate' and 'bs2b_set_level' functions (or 'bs2b_set_srate', 'bs2b_set_level_fcut', 'bs2b_set_level_feed') accordingly.
Table 2. Example of using of bs2b library (C++).
#include <stdio.h>
#include "bs2bclass.h"
int main()
{
bs2b_base bs2b;
// Default init value
//bs2b.set_srate( 44100 );
//bs2b.set_level( BS2B_DEFAULT_CLEVEL ); // 700 Hz, 4.5 dB
// or another way
//bs2b.set_srate( 44100 );
//bs2b.set_level_fcut( 700 ); // 700 Hz
//bs2b.set_level_feed( 45 ); // 4.5 dB
// raw LPCM, signed 16 bit, native to CPU byte order, stereo interleaved
short sample[ 2 ];
while( 2 == fread( sample, sizeof( short ), 2, stdin ) )
{
bs2b.cross_feed( sample );
fwrite( sample, sizeof( short ), 2, stdout );
}
return 0 ;
}
You can use a 'bs2bstream' with 'lame' by a command line like this:
lame -t --decode test.wav - | bs2bstream | lame -r -x -m j -s 44.1 --bitwidth 16 --preset extreme - test.mp3
or without of '-x' swap bytes of input file, like this:
lame -t --decode test.wav - | bs2bstream | lame -r -m j -s 44.1 --bitwidth 16 --preset extreme - test.mp3
There is a bash script below for example of using of bs2bstream.
Table 3. Example of using of bs2bstream (bash).
#!/bin/bash
# FLAC player using the bs2b DSP
#
# (c) 2011 Bart Lauret
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
# Do not loop though files when no flac exists:
shopt -s nullglob
# Change this to your soundcard's address
# If your soundcard supports S16_LE and S24_3LE, use hw:X,X to circumvent software resampling
DEVICE="plughw:0,0"
function checkplay {
if [ `soxi -V0 -c "$FILE"` -eq "2" ]; then
RATE=`soxi -V0 -r "$FILE"`
RATEKHZ=`echo "scale=1 ; $RATE / 1000" | bc`
case `soxi -V0 -b "$FILE"` in
16) play16;;
24) play24;;
*) echo "File format not supported: use FLACs with 16 or 24 bit resolution.";;
esac
else
echo "File is mono, crossfeed not possible..."
fi
}
function play16 {
echo "*** Playing $FILE... (16 bit/$RATEKHZ kHz)"
if [ "$CROSSFEED" ]; then
flac --endian=little --sign=signed --force-raw-format --totally-silent -dc "$FILE" | \
bs2bstream -e l -b 16 -r "$RATEKHZ" -l "$CROSSFEED" | \
aplay -c 2 -r "$RATE" -f S16_LE -D "$DEVICE" -t raw --quiet
else
echo "*** No crossfeed selected, playing without..."
flac --totally-silent -dc "$FILE" | \
aplay -c 2 -r "$RATE" -f S16_LE -D "$DEVICE" -t wav --quiet
fi
}
function play24 {
echo "*** Playing $FILE... (24 bit/$RATEKHZ kHz)"
if [ "$CROSSFEED" ]; then
flac --endian=little --sign=signed --force-raw-format --totally-silent -dc "$FILE" | \
bs2bstream -e l -b 24 -r "$RATEKHZ" -l "$CROSSFEED" | \
aplay -c 2 -r "$RATE" -f S24_3LE -D "$DEVICE" -t raw --quiet
else
echo "*** No crossfeed selected, playing without..."
flac --totally-silent -dc "$FILE" | \
aplay -c 2 -r "$RATE" -f S24_3LE -D "$DEVICE" -t wav --quiet
fi
}
function usage {
echo "Usage:"
echo "Play a single file: bs2b [-dcm] -f <filename>"
echo "Play all FLACs in a directory: bs2b [-dcm] -D"
echo
echo " -d - default preset - 700Hz/260us, 4.5 dB;"
echo " -c - Chu Moy's preset - 700Hz/260us, 6.0 dB;"
echo " -m - Jan Meier's preset - 650Hz/280us, 9.5 dB."
echo
}
# Script starts here
echo "bs2b - FLAC player with Bauer stereophonic-to-binaural DSP"
echo "bs2b comes with ABSOLUTELY NO WARRANTY. This is free software, and you are"
echo "welcome to redistribute it under certain conditions."
echo
if [ ! `which soxi` ]; then
echo "Please install sox. For more information see http://sox.sourceforge.net/"
if [ ! `which flac` ]; then
echo "Please install flac. For more information see http://flac.sourceforge.net/"
fi
exit 1
fi
while getopts "dcmDf:" flag
do
case "$flag" in
d) CROSSFEED="$flag"; echo "*** Crossfeed set to default preset.";;
c) CROSSFEED="$flag"; echo "*** Crossfeed set to Chu Moy's preset.";;
m) CROSSFEED="$flag"; echo "*** Crossfeed set to Jan Meier's preset.";;
D) DIR="$OPTIND";;
f) FILE="$OPTARG"
esac
done
if [ -f "$FILE" ]; then
checkplay
elif [ $DIR ]; then
for FILE in *.flac
do
checkplay
done
else
usage
exit 1
fi
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© Boris Mikhaylov