Commit 12f0b200 authored by Jean-Paul Saman's avatar Jean-Paul Saman

Added fixed32tos16 filter based upon libmad downscale functionality.

parent c95d91b4
/*****************************************************************************
* fixed32tos16.c : converter from fised32 to signed 16 bits integer
*****************************************************************************
* Copyright (C) 2002 VideoLAN
* $Id: fixed32tos16.c,v 1.1 2002/08/12 20:34:56 jpsaman Exp $
*
* Authors: Jean-Paul Saman <jpsaman@wxs.nl>
*
* 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., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
*****************************************************************************/
/*****************************************************************************
* Preamble
*****************************************************************************/
#include <errno.h>
#include <stdlib.h> /* malloc(), free() */
#include <string.h>
#include <vlc/vlc.h>
#include "audio_output.h"
#include "aout_internal.h"
/*****************************************************************************
* Local prototypes
*****************************************************************************/
static int Create ( vlc_object_t * );
static void DoWork ( aout_instance_t *, aout_filter_t *, aout_buffer_t *,
aout_buffer_t * );
/*****************************************************************************
* Module descriptor
*****************************************************************************/
vlc_module_begin();
set_description( _("aout filter for fixed32->s16 conversion") );
set_capability( "audio filter", 10 );
set_callbacks( Create, NULL );
vlc_module_end();
/*****************************************************************************
* Create: allocate trivial mixer
*****************************************************************************
* This function allocates and initializes a Crop vout method.
*****************************************************************************/
static int Create( vlc_object_t *p_this )
{
aout_filter_t * p_filter = (aout_filter_t *)p_this;
if ( p_filter->input.i_format != AOUT_FMT_FIXED32
&& p_filter->output.i_format != AOUT_FMT_S16_NE )
{
return -1;
}
if ( p_filter->input.i_rate != p_filter->output.i_rate
|| p_filter->input.i_channels != p_filter->output.i_channels )
{
return -1;
}
p_filter->pf_do_work = DoWork;
p_filter->b_in_place = 1;
printf( "fixed32tos16 spawned.\n" );
return 0;
}
/*****************************************************************************
* support routines borrowed from mpg321 (file: mad.c), which is distributed
* under GPL license
*
* mpg321 was written by Joe Drew <drew@debian.org>, and based upon 'plaympeg'
* from the smpeg sources, which was written by various people from Loki Software
* (http://www.lokigames.com).
*
* It also incorporates some source from mad, written by Robert Leslie
*****************************************************************************/
/* The following two routines and data structure are from the ever-brilliant
Rob Leslie.
*/
#define VLC_F_FRACBITS 28
# if VLC_F_FRACBITS == 28
# define VLC_F(x) ((vlc_fixed_t) (x##L))
# endif
# define VLC_F_ONE VLC_F(0x10000000)
struct audio_dither {
vlc_fixed_t error[3];
vlc_fixed_t random;
};
/********************************************************************
* NAME: prng()
* DESCRIPTION: 32-bit pseudo-random number generator
********************************************************************/
static inline unsigned long prng(unsigned long state)
{
return (state * 0x0019660dL + 0x3c6ef35fL) & 0xffffffffL;
}
/********************************************************************
* NAME: mpg321_s24_to_s16_pcm()
* DESCRIPTION: generic linear sample quantize and dither routine
********************************************************************/
static inline s16 mpg321_s24_to_s16_pcm(unsigned int bits, vlc_fixed_t sample,
struct audio_dither *dither)
{
unsigned int scalebits;
vlc_fixed_t output, mask, random;
enum {
MIN = -VLC_F_ONE,
MAX = VLC_F_ONE - 1
};
/* noise shape */
sample += dither->error[0] - dither->error[1] + dither->error[2];
dither->error[2] = dither->error[1];
dither->error[1] = dither->error[0] / 2;
/* bias */
output = sample + (1L << (VLC_F_FRACBITS + 1 - bits - 1));
scalebits = VLC_F_FRACBITS + 1 - bits;
mask = (1L << scalebits) - 1;
/* dither */
random = prng(dither->random);
output += (random & mask) - (dither->random & mask);
dither->random = random;
/* clip */
if (output > MAX) {
output = MAX;
if (sample > MAX)
sample = MAX;
}
else if (output < MIN) {
output = MIN;
if (sample < MIN)
sample = MIN;
}
/* quantize */
output &= ~mask;
/* error feedback */
dither->error[0] = sample - output;
/* scale */
return output >> scalebits;
}
/*****************************************************************************
* s24_to_s16_pcm: Scale a 24 bit pcm sample to a 16 bit pcm sample.
*****************************************************************************/
static inline s16 s24_to_s16_pcm(vlc_fixed_t sample)
{
/* round */
sample += (1L << (VLC_F_FRACBITS - 16));
/* clip */
if (sample >= VLC_F_ONE)
sample = VLC_F_ONE - 1;
else if (sample < -VLC_F_ONE)
sample = -VLC_F_ONE;
/* quantize */
return (sample >> (VLC_F_FRACBITS + 1 - 16));
}
/*****************************************************************************
* DoWork: convert a buffer
*****************************************************************************/
static void DoWork( aout_instance_t * p_aout, aout_filter_t * p_filter,
aout_buffer_t * p_in_buf, aout_buffer_t * p_out_buf )
{
int i;
vlc_fixed_t * p_in = (vlc_fixed_t *)p_in_buf->p_buffer;
s16 * p_out = (s16 *)p_out_buf->p_buffer;
s16 sample;
// static struct audio_dither dither;
for ( i = 0; i < p_in_buf->i_nb_samples * p_filter->input.i_channels; i++ )
{
/* Accurate scaling */
// p_out = mpg321_s24_to_s16_pcm(16, *p_in++, &dither);
/* Fast Scaling */
sample = s24_to_s16_pcm(*p_in++);
#ifndef WORDS_BIGENDIAN
*p_out++ = (s16) (sample >> 0);
*p_out++ = (s16) (sample >> 8);
#else
*p_out++ = (s16) (sample >> 8);
*p_out++ = (s16) (sample >> 0);
#endif
// p_in++; p_out++;
}
p_out_buf->i_nb_samples = p_in_buf->i_nb_samples;
}
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