FreeCalypso > hg > freecalypso-tools
view miscutil/fc-tch2fr.c @ 416:30f6d1c32c6f
doc/Flash-boot-defect article removed (no longer relevant)
This article is no longer relevant because the issue in question
only affected one (1) defective FCDEV3B board which was not
and never will be sold.
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 26 Oct 2018 07:11:08 +0000 |
parents | d57f68d0568d |
children |
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/* * Our experimental Calypso firmware enables us to capture the output of * the GSM 05.03 channel decoder in the DSP, i.e., the bits leaving the * channel decoder and going into the speech decoder. Our fc-shell utility * allows saving this capture to a file; the captured booty includes not only * the expected 260 bits per frame, but also some DSP status words which are * not fully understood, but which are believed to contain indications as to * whether the decoded speech frame is good or bad. * * My first naive thought was to save the captured speech frames in libgsm * format so I could then play them with the 'play' command (SoX package) * under Linux, but the problem with this naive approach is that the bad frames * indication is lost, and some of the saved "speech" frames will contain * utter garbage, resulting in very unkind-on-ears noises if that file is * then played. I don't know what the proper solution should be; I don't know * what the commercial cellphone implementations of the GSM 06.10 speech decoder * (buried in black box DSPs) do when they get bad frames from the channel * decoder. * * The present utility reproduces the naive behaviour of my previous * implementation of fc-shell's tch record command: it takes hex files written * by the current implementation of tch record in fc-shell, DISREGARDS the * DSP status words, and blindly converts each 260-bit frame (good or bad) * into libgsm format. */ #include <sys/types.h> #include <ctype.h> #include <stdio.h> #include <stdlib.h> static decode_hex_digit(ch) { if (isdigit(ch)) return(ch - '0'); else if (isupper(ch)) return(ch - 'A' + 10); else return(ch - 'a' + 10); } main(argc, argv) char **argv; { FILE *inf, *outf; char linebuf[128]; int lineno; char *cp; int i, j; u_char tidsp_bytes[33], libgsm_bytes[33]; if (argc != 3) { fprintf(stderr, "usage: %s infile outfile\n", argv[0]); exit(1); } inf = fopen(argv[1], "r"); if (!inf) { perror(argv[1]); exit(1); } outf = fopen(argv[2], "w"); if (!outf) { perror(argv[2]); exit(1); } for (lineno = 1; fgets(linebuf, sizeof linebuf, inf); lineno++) { /* skip DSP status words */ cp = linebuf; for (i = 0; i < 3; i++) { for (j = 0; j < 4; j++) { if (!isxdigit(*cp++)) { invalid: fprintf(stderr, "error: %s is not in the expected format\n", argv[1]); exit(1); } } if (*cp++ != ' ') goto invalid; } /* read the frame bits */ for (i = 0; i < 33; i++) { if (!isxdigit(cp[0]) || !isxdigit(cp[1])) goto invalid; tidsp_bytes[i] = (decode_hex_digit(cp[0]) << 4) | decode_hex_digit(cp[1]); cp += 2; } gsm0610_tidsp_to_libgsm(tidsp_bytes, libgsm_bytes); fwrite(libgsm_bytes, 1, 33, outf); } exit(0); }