mirror of
https://codeberg.org/canoeboot/cbmk.git
synced 2024-12-22 07:49:55 +00:00
124 lines
2.9 KiB
C
124 lines
2.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
|
|
/* SPDX-FileCopyrightText: 2013 Free Software Foundation, Inc. */
|
|
/* Usage: parec --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv */
|
|
|
|
/* Forked from coreboot's version, at util/spkmodem_recv/ in coreboot.git,
|
|
* revision 5c2b5fcf2f9c9259938fd03cfa3ea06b36a007f0 as of 3 January 2022.
|
|
* This version is heavily modified, re-written based on OpenBSD Kernel Source
|
|
* File Style Guide (KNF); this change is Copyright 2023 Leah Rowe. */
|
|
|
|
#include <err.h>
|
|
#include <errno.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
|
|
#define SAMPLES_PER_FRAME 240
|
|
#define MAX_SAMPLES (2 * SAMPLES_PER_FRAME)
|
|
#define FREQ_SEP_MIN 5
|
|
#define FREQ_SEP_MAX 15
|
|
#define FREQ_DATA_MIN 15
|
|
#define FREQ_DATA_THRESHOLD 25
|
|
#define FREQ_DATA_MAX 60
|
|
#define THRESHOLD 500
|
|
|
|
#define ERR() (errno = errno ? errno : ECANCELED)
|
|
#define reset_char() ascii = 0, ascii_bit = 7
|
|
|
|
signed short frame[MAX_SAMPLES], pulse[MAX_SAMPLES];
|
|
int ringpos, debug, freq_data, freq_separator, sample_count, ascii_bit = 7;
|
|
char ascii = 0;
|
|
|
|
void handle_audio(void);
|
|
void decode_pulse(void);
|
|
int set_ascii_bit(void);
|
|
void print_char(void);
|
|
void print_stats(void);
|
|
|
|
int
|
|
main(int argc, char *argv[])
|
|
{
|
|
int c;
|
|
#ifdef __OpenBSD__
|
|
if (pledge("stdio", NULL) == -1)
|
|
err(ERR(), "pledge");
|
|
#endif
|
|
while ((c = getopt(argc, argv, "d")) != -1)
|
|
if (!(debug = (c == 'd')))
|
|
err(errno = EINVAL, NULL);
|
|
setvbuf(stdout, NULL, _IONBF, 0);
|
|
while (!feof(stdin))
|
|
handle_audio();
|
|
if (errno && debug)
|
|
err(errno, "Unhandled error, errno %d", errno);
|
|
return errno;
|
|
}
|
|
|
|
void
|
|
handle_audio(void)
|
|
{
|
|
if (sample_count > (3 * SAMPLES_PER_FRAME))
|
|
sample_count = reset_char();
|
|
if ((freq_separator <= FREQ_SEP_MIN) || (freq_separator >= FREQ_SEP_MAX)
|
|
|| (freq_data <= FREQ_DATA_MIN) || (freq_data >= FREQ_DATA_MAX)) {
|
|
decode_pulse();
|
|
return;
|
|
}
|
|
|
|
if (set_ascii_bit() < 0)
|
|
print_char();
|
|
sample_count = 0;
|
|
for (int sample = 0; sample < SAMPLES_PER_FRAME; sample++)
|
|
decode_pulse();
|
|
}
|
|
|
|
void
|
|
decode_pulse(void)
|
|
{
|
|
int next_ringpos = (ringpos + SAMPLES_PER_FRAME) % MAX_SAMPLES;
|
|
freq_data -= pulse[ringpos];
|
|
freq_data += pulse[next_ringpos];
|
|
freq_separator -= pulse[next_ringpos];
|
|
|
|
fread(frame + ringpos, 1, sizeof(frame[0]), stdin);
|
|
if (ferror(stdin) != 0)
|
|
err(ERR(), "Could not read from frame.");
|
|
|
|
if ((pulse[ringpos] = (abs(frame[ringpos]) > THRESHOLD) ? 1 : 0))
|
|
++freq_separator;
|
|
++ringpos;
|
|
ringpos %= MAX_SAMPLES;
|
|
++sample_count;
|
|
}
|
|
|
|
int
|
|
set_ascii_bit(void)
|
|
{
|
|
if (debug)
|
|
print_stats();
|
|
if (freq_data < FREQ_DATA_THRESHOLD)
|
|
ascii |= (1 << ascii_bit);
|
|
--ascii_bit;
|
|
return ascii_bit;
|
|
}
|
|
|
|
void
|
|
print_char(void)
|
|
{
|
|
if (debug)
|
|
printf("<%c, %x>", ascii, ascii);
|
|
else
|
|
printf("%c", ascii);
|
|
reset_char();
|
|
}
|
|
|
|
void
|
|
print_stats(void)
|
|
{
|
|
long stdin_pos;
|
|
if ((stdin_pos = ftell(stdin)) == -1)
|
|
err(ERR(), NULL);
|
|
printf ("%d %d %d @%ld\n", freq_data, freq_separator,
|
|
FREQ_DATA_THRESHOLD, stdin_pos - sizeof(frame));
|
|
}
|