120 lines
3.6 KiB
C
120 lines
3.6 KiB
C
|
/*
|
||
|
|
* This source code is a product of Sun Microsystems, Inc. and is provided
|
||
|
|
* for unrestricted use. Users may copy or modify this source code without
|
||
|
|
* charge.
|
||
|
|
*
|
||
|
|
* SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
|
||
|
|
* THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
|
||
|
|
* PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
|
||
|
|
*
|
||
|
|
* Sun source code is provided with no support and without any obligation on
|
||
|
|
* the part of Sun Microsystems, Inc. to assist in its use, correction,
|
||
|
|
* modification or enhancement.
|
||
|
|
*
|
||
|
|
* SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
|
||
|
|
* INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
|
||
|
|
* OR ANY PART THEREOF.
|
||
|
|
*
|
||
|
|
* In no event will Sun Microsystems, Inc. be liable for any lost revenue
|
||
|
|
* or profits or other special, indirect and consequential damages, even if
|
||
|
|
* Sun has been advised of the possibility of such damages.
|
||
|
|
*
|
||
|
|
* Sun Microsystems, Inc.
|
||
|
|
* 2550 Garcia Avenue
|
||
|
|
* Mountain View, California 94043
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
* g711.h
|
||
|
|
*
|
||
|
|
* u-law, A-law and linear PCM conversions.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#ifndef G711_H
|
||
|
|
#define G711_H
|
||
|
|
|
||
|
|
#ifdef __cplusplus
|
||
|
|
extern "C" {
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/*
|
||
|
|
* linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
|
||
|
|
*
|
||
|
|
* linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
|
||
|
|
*
|
||
|
|
* Linear Input Code Compressed Code
|
||
|
|
* ------------------------ ---------------
|
||
|
|
* 0000000wxyza 000wxyz
|
||
|
|
* 0000001wxyza 001wxyz
|
||
|
|
* 000001wxyzab 010wxyz
|
||
|
|
* 00001wxyzabc 011wxyz
|
||
|
|
* 0001wxyzabcd 100wxyz
|
||
|
|
* 001wxyzabcde 101wxyz
|
||
|
|
* 01wxyzabcdef 110wxyz
|
||
|
|
* 1wxyzabcdefg 111wxyz
|
||
|
|
*
|
||
|
|
* For further information see John C. Bellamy's Digital Telephony, 1982,
|
||
|
|
* John Wiley & Sons, pps 98-111 and 472-476.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* pcm_val is 2's complement (16-bit range) */
|
||
|
|
unsigned char _af_linear2alaw (int pcm_val);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* alaw2linear() - Convert an A-law value to 16-bit linear PCM
|
||
|
|
*
|
||
|
|
*/
|
||
|
|
|
||
|
|
int _af_alaw2linear (unsigned char a_val);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* linear2ulaw() - Convert a linear PCM value to u-law
|
||
|
|
*
|
||
|
|
* In order to simplify the encoding process, the original linear magnitude
|
||
|
|
* is biased by adding 33 which shifts the encoding range from (0 - 8158) to
|
||
|
|
* (33 - 8191). The result can be seen in the following encoding table:
|
||
|
|
*
|
||
|
|
* Biased Linear Input Code Compressed Code
|
||
|
|
* ------------------------ ---------------
|
||
|
|
* 00000001wxyza 000wxyz
|
||
|
|
* 0000001wxyzab 001wxyz
|
||
|
|
* 000001wxyzabc 010wxyz
|
||
|
|
* 00001wxyzabcd 011wxyz
|
||
|
|
* 0001wxyzabcde 100wxyz
|
||
|
|
* 001wxyzabcdef 101wxyz
|
||
|
|
* 01wxyzabcdefg 110wxyz
|
||
|
|
* 1wxyzabcdefgh 111wxyz
|
||
|
|
*
|
||
|
|
* Each biased linear code has a leading 1 which identifies the segment
|
||
|
|
* number. The value of the segment number is equal to 7 minus the number
|
||
|
|
* of leading 0's. The quantization interval is directly available as the
|
||
|
|
* four bits wxyz. * The trailing bits (a - h) are ignored.
|
||
|
|
*
|
||
|
|
* Ordinarily the complement of the resulting code word is used for
|
||
|
|
* transmission, and so the code word is complemented before it is returned.
|
||
|
|
*
|
||
|
|
* For further information see John C. Bellamy's Digital Telephony, 1982,
|
||
|
|
* John Wiley & Sons, pps 98-111 and 472-476.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* pcm_val is 2's complement (16-bit range) */
|
||
|
|
unsigned char _af_linear2ulaw (int pcm_val);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* ulaw2linear() - Convert a u-law value to 16-bit linear PCM
|
||
|
|
*
|
||
|
|
* First, a biased linear code is derived from the code word. An unbiased
|
||
|
|
* output can then be obtained by subtracting 33 from the biased code.
|
||
|
|
*
|
||
|
|
* Note that this function expects to be passed the complement of the
|
||
|
|
* original code word. This is in keeping with ISDN conventions.
|
||
|
|
*/
|
||
|
|
|
||
|
|
int _af_ulaw2linear (unsigned char u_val);
|
||
|
|
|
||
|
|
#ifdef __cplusplus
|
||
|
|
}
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#endif /* G711_H */
|