FreeCalypso > hg > gsm-codec-lib
view miscutil/pcm16-to-ulaw.c @ 282:9ee8ad3d4d30
frtest: rm gsmfr-hand-test and gsmfr-max-out utils
These hack programs were never properly documented and were written
only as part of a debug chase, in pursuit of a bug that ultimately
turned out to be in our then-hacky patch to osmo-bts-sysmo,
before beginning of proper patches in Osmocom. These hack programs
need to be dropped from the present sw package because they depend
on old libgsm, and we are eliminating that dependency.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Sun, 14 Apr 2024 05:44:47 +0000 |
parents | c7f02428bda6 |
children |
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/* * This program reads a 16-bit PCM recording in raw format (robe by default, * or LE with -l option) and converts it to 8-bit PCM in North American * mu-law encoding. It is based on the ulaw_compress() function from ITU-T * G.191 STL, using the most significant 14 bits of each input linear PCM * sample, rather than just 13. A command line option is also provided * to truncate each input value to 13 bits prior to mu-law encoding, to * replicate the effect of using a table lookup conversion method that * only considers the upper 13 bits - specify -t option to select this mode. */ #include <stdio.h> #include <stdint.h> #include <stdlib.h> #include <string.h> #include <strings.h> #include <unistd.h> static unsigned ulaw_compress(input) unsigned input; { short i; /* aux.var. */ short absno; /* absolute value of linear (input) sample */ short segno; /* segment (Table 2/G711, column 1) */ short low_nibble; /* low nibble of log companded sample */ short high_nibble; /* high nibble of log companded sample */ unsigned output; /* -------------------------------------------------------------------- */ /* Input is 14-bit right-justified in this version */ /* Compute absolute value; adjust for easy processing */ /* -------------------------------------------------------------------- */ absno = input >= 0x2000 /* compute 1's complement in case of */ ? (~input & 0x1FFF) + 33 /* negative samples */ : input + 33; /* NB: 33 is the difference value */ /* between the thresholds for */ /* A-law and u-law. */ if (absno > (0x1FFF)) /* limitation to "absno" < 8192 */ absno = (0x1FFF); /* Determination of sample's segment */ i = absno >> 6; segno = 1; while (i != 0) { segno++; i >>= 1; } /* Mounting the high-nibble of the log-PCM sample */ high_nibble = (0x0008) - segno; /* Mounting the low-nibble of the log PCM sample */ low_nibble = (absno >> segno) /* right shift of mantissa and */ &(0x000F); /* masking away leading '1' */ low_nibble = (0x000F) - low_nibble; /* Joining the high-nibble and the low-nibble of the log PCM sample */ output = (high_nibble << 4) | low_nibble; /* Add sign bit */ if (input < 0x2000) output = output | (0x0080); return output; } main(argc, argv) char **argv; { int opt, little_endian = 0, truncate = 0; char *infname, *outfname; FILE *inf, *outf; uint8_t inb[2]; uint16_t ins; int cc; extern int optind; while ((opt = getopt(argc, argv, "lt")) != EOF) { switch (opt) { case 'l': little_endian = 1; continue; case 't': truncate = 1; continue; default: usage: fprintf(stderr, "usage: %s [-l] [-t] input.pcm16 output.ulaw\n", argv[0]); exit(1); } } if (argc != optind + 2) goto usage; infname = argv[optind]; outfname = argv[optind+1]; inf = fopen(infname, "r"); if (!inf) { perror(infname); exit(1); } outf = fopen(outfname, "w"); if (!outf) { perror(outfname); exit(1); } for (;;) { cc = fread(inb, 1, 2, inf); if (cc <= 0) break; if (cc & 1) { fprintf(stderr, "error: %s has odd number of bytes\n", infname); exit(1); } if (little_endian) ins = ((uint16_t) inb[1] << 8) | ((uint16_t) inb[0]); else ins = ((uint16_t) inb[0] << 8) | ((uint16_t) inb[1]); ins >>= 2; if (truncate) ins &= ~1; putc(ulaw_compress(ins), outf); } fclose(outf); exit(0); }