loudness.c

用 Hitex 工具软件开发 stm32 的例子

/********************************************************************
 * Project:    Tasking-STM32-Stick
 * File:       loudness.c
 *
 * System:     Cortex ARMv7 32 Bit (STM32FRT)
 * Compiler:   Tasking Altuim VX Toolchain v2.01
 *
 * Date:       2007-08-20
 * Author:     [e-mail]
 *
 * Rights:     Hitex Development Tools GmbH
 *             Greschbachstr. 12
 *             D-76229 Karlsruhe
 ********************************************************************
 * Description:
 *
 * This file is part of the Tasking Example chain
 * The code is based on usage of the STmicro library functions
 * This is a small implementation of different features
 * The application runs in ARM mode with high optimization level.
 * loudness.c - loudness of the signal
 *
 *    loud()      calculates the loudness of the signal, for
 *                each freq point. Result is an integer array,
 *                units are dB (values will be negative).
 *
 *       All data are fixed-point short integers, in which
 *       -32768 to +32768 represent -1.0 to +1.0. Integer arithmetic
 *       is used for speed, instead of the more natural floating-point.
 *
 ********************************************************************
 * History:
 *
 *    Revision 1.0    2007/08/20      Gn
 *    Initial revision
 ********************************************************************
 * This is a preliminary version.
 *
 * WARRANTY:  HITEX warrants that the media on which the SOFTWARE is
 * furnished is free from defects in materials and workmanship under
 * normal use and service for a period of ninety (90) days. HITEX entire
 * liability and your exclusive remedy shall be the replacement of the
 * SOFTWARE if the media is defective. This Warranty is void if failure
 * of the media resulted from unauthorized modification, accident, abuse,
 * or misapplication.
 *
 * DISCLAIMER:  OTHER THAN THE ABOVE WARRANTY, THE SOFTWARE IS FURNISHED
 * "AS IS" WITHOUT WARRANTY OF ANY KIND. HITEX DISCLAIMS ALL OTHER WARRANTIES,
 * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * NEITHER HITEX NOR ITS AFFILIATES SHALL BE LIABLE FOR ANY DAMAGES ARISING
 * OUT OF THE USE OF OR INABILITY TO USE THE SOFTWARE, INCLUDING DAMAGES FOR
 * LOSS OF PROFITS, BUSINESS INTERRUPTION, OR ANY SPECIAL, INCIDENTAL, INDIRECT
 * OR CONSEQUENTIAL DAMAGES EVEN IF HITEX HAS BEEN ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGES.
 ********************************************************************/

#include "FFTfunc.h"

int db_from_ampl(short re, short im);

/**
   loudness() - compute loudness of freq-spectrum components.
   n should be ntot/2, where ntot was passed to fix_fft();
   6 dB is added to account for the omitted alias components.
   loud[] is the loudness, in dB wrt 32767; will be +10 to -N_LOUD.
*/
void loudness(short loud[], short fr[], short fi[])
{
   int i;

   for(i=0; i<N_SAMPLE/2; ++i)
   {
      loud[i] = db_from_ampl(fr[i],fi[i]) + 6;
      if(loud[i] > 0) loud[i] = 0;
      loud[i] = -loud[i];
   }
}

/**
   db_from_ampl() - find loudness (in dB) from
   the complex amplitude.
*/
int db_from_ampl(short re, short im)
{
   long v;
   int i;

   v = (long)re * (long)re + (long)im * (long)im;

   for(i=0; i<N_LOUD; ++i)
      if(loudness_table[i] <= v)
         break;

   return (-i);
}