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+The files in this directory comprise ANSI-C language reference implementations
+of the CCITT (International Telegraph and Telephone Consultative Committee)
+G.711, G.721 and G.723 voice compressions. They have been tested on Sun
+SPARCstations and passed 82 out of 84 test vectors published by CCITT
+(Dec. 20, 1988) for G.721 and G.723. [The two remaining test vectors,
+which the G.721 decoder implementation for u-law samples did not pass,
+may be in error because they are identical to two other vectors for G.723_40.]
+This source code is released by Sun Microsystems, Inc. to the public domain.
+Please give your acknowledgement in product literature if this code is used
+in your product implementation.
+Sun Microsystems supports some CCITT audio formats in Solaris 2.0 system
+software. However, Sun's implementations have been optimized for higher
+performance on SPARCstations.
+The source files for CCITT conversion routines in this directory are:
+ g72x.h header file for g721.c, g723_24.c and g723_40.c
+ g711.c CCITT G.711 u-law and A-law compression
+ g72x.c common denominator of G.721 and G.723 ADPCM codes
+ g721.c CCITT G.721 32Kbps ADPCM coder (with g72x.c)
+ g723_24.c CCITT G.723 24Kbps ADPCM coder (with g72x.c)
+ g723_40.c CCITT G.723 40Kbps ADPCM coder (with g72x.c)
+Simple conversions between u-law, A-law, and 16-bit linear PCM are invoked
+as follows:
+ unsigned char ucode, acode;
+ short pcm_val;
+ ucode = linear2ulaw(pcm_val);
+ ucode = alaw2ulaw(acode);
+ acode = linear2alaw(pcm_val);
+ acode = ulaw2alaw(ucode);
+ pcm_val = ulaw2linear(ucode);
+ pcm_val = alaw2linear(acode);
+The other CCITT compression routines are invoked as follows:
+ #include "g72x.h"
+ struct g72x_state state;
+ int sample, code;
+ g72x_init_state(&state);
+ code = {g721,g723_24,g723_40}_encoder(sample, coding, &state);
+ sample = {g721,g723_24,g723_40}_decoder(code, coding, &state);
+ coding = AUDIO_ENCODING_ULAW for 8-bit u-law samples
+ AUDIO_ENCODING_ALAW for 8-bit A-law samples
+ AUDIO_ENCODING_LINEAR for 16-bit linear PCM samples
+This directory also includes the following sample programs:
+ encode.c CCITT ADPCM encoder
+ decode.c CCITT ADPCM decoder
+ Makefile makefile for the sample programs
+The sample programs contain examples of how to call the various compression
+routines and pack/unpack the bits. The sample programs read byte streams from
+stdin and write to stdout. The input/output data is raw data (no file header
+or other identifying information is embedded). The sample programs are
+invoked as follows:
+ encode [-3|4|5] [-a|u|l] <infile >outfile
+ decode [-3|4|5] [-a|u|l] <infile >outfile
+ -3 encode to (decode from) G.723 24kbps (3-bit) data
+ -4 encode to (decode from) G.721 32kbps (4-bit) data [the default]
+ -5 encode to (decode from) G.723 40kbps (5-bit) data
+ -a encode from (decode to) A-law data
+ -u encode from (decode to) u-law data [the default]
+ -l encode from (decode to) 16-bit linear data
+ # Read 16-bit linear and output G.721
+ encode -4 -l <pcmfile >g721file
+ # Read 40Kbps G.723 and output A-law
+ decode -5 -a <g723file >alawfile
+ # Compress and then decompress u-law data using 24Kbps G.723
+ encode -3 <ulawin | deoced -3 >ulawout