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