FreeCalypso > hg > gsm-codec-lib
view dev/a2s-regen.c @ 477:4c9222d95647
libtwamr encoder: always emit frame->mode = mode;
In the original implementation of amr_encode_frame(), the 'mode' member
of the output struct was set to 0xFF if the output frame type is TX_NO_DATA.
This design was made to mimic the mode field (16-bit word) being set to
0xFFFF (or -1) in 3GPP test sequence format - but nothing actually depends
on this struct member being set in any way, and amr_frame_to_tseq()
generates the needed 0xFFFF on its own, based on frame->type being equal
to TX_NO_DATA.
It is simpler and more efficient to always set frame->mode to the actual
encoding mode in amr_encode_frame(), and this new behavior has already
been documented in doc/AMR-library-API description in anticipation of
the present change.
author | Mychaela Falconia <falcon@freecalypso.org> |
---|---|
date | Sat, 18 May 2024 22:30:42 +0000 |
parents | ba737a0203e2 |
children |
line wrap: on
line source
/* * 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); }