man3/AF_gain_table_a.3

#

    AF_gain_table_u(3)					   AF_gain_table_u(3)

    NAME
      AF_gain_table_u, AF_gain_table_a - ULAW and ALAW gain	tables

    SYNTAX
      #include <AF/AFUtils.h>

      extern int AF_gain_min_u, AF_gain_max_u;

      extern unsigned char *AF_gain_table_u[];

      extern int AF_gain_min_a, AF_gain_max_a;

      extern unsigned char *AF_gain_table_a[];

    DESCRIPTION
      AF_gain_table_u is an	array of precomputed gain tables for ULAW samples.
      AF_gain_table_a is the same thing, but for ALAW samples.  These tables are
      useful for effectivly	decompressing a	sample,	multiplying by a constant,
      and recompressing.  The tables are available in 1 dB steps from
      AF_gain_min_u	to AF_gain_max_u for ULAW samples.  (or	from AF_gain_min_a to
      AF_gain_max_a	for ALAW samples.)

    EXAMPLES
      Typical usage	is:

      unsigned char	*gain_table;
      unsigned char	input, output;
      /* first select a particular table, for 5 dB gain */
      gain_table = AF_gain_table_u[	5 - AF_gain_min_u ];
      /* now translate the sample */
      output = gain_table[ input ];

    DIAGNOSTICS
      If you index the table with an out-of-range linear value you may cause a
      protection fault and crash your application.

    SEE ALSO
      AF(1)

    BUGS
      If you encounter a reproducible bug, please submit a problem report to
      (af-bugs@crl.dec.com).

    COPYRIGHT
      Copyright 1990-1994, Digital Equipment Corporation.
      See AF(1) for	a full statement of rights and permissions.

    AUTHORS
      Tom Levergood	and Larry Stewart, Digital Cambridge Research Lab