FreeCalypso > hg > gsm-codec-lib
view dev/a2s-regen.c @ 384:a8dab7028e4d
libtwamr: integrate lag_wind.c
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Mon, 06 May 2024 05:56:50 +0000 |
parents | ba737a0203e2 |
children |
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/* * This program regenerates a G.711 A-law decoding table equivalent to the * a2s[] table in the toast_alaw.c module in libgsm/toast; the intent is * to check that table for correctness. The "engine" function that does * the computation is based on alaw_expand() from ITU-T G.191 STL. */ #include <stdio.h> #include <stdlib.h> static unsigned alaw_expand (input) unsigned input; { short ix, mant, iexp; ix = input ^ (0x0055); /* re-toggle toggled bits */ ix &= (0x007F); /* remove sign bit */ iexp = ix >> 4; /* extract exponent */ mant = ix & (0x000F); /* now get mantissa */ if (iexp > 0) mant = mant + 16; /* add leading '1', if exponent > 0 */ mant = (mant << 4) + (0x0008); /* now mantissa left justified and */ /* 1/2 quantization step added */ if (iexp > 1) /* now left shift according exponent */ mant = mant << (iexp - 1); if (input & 0x80) /* invert, if negative sample */ return mant; else return -mant & 0xFFFF; } main(argc, argv) char **argv; { unsigned input, output; for (input = 0; input < 256; input++) { output = alaw_expand(input); printf("%6u,", output); if ((input & 7) == 7) putchar('\n'); } exit(0); }