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util/spkmodem-decode: annotate prototypes

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Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-13 01:23:27 +00:00
parent 7c88154cd2
commit 681f580053
1 changed files with 117 additions and 98 deletions
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util/spkmodem_decode/spkmodem-decode.c
+117 -98
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@@ -213,25 +213,44 @@ struct decoder_state {
static const char *argv0;
/*
* 16-bit little endian words are read
* continuously. we will swap them, if
* the host cpu is big endian.
*/
static int host_is_big_endian(void);
/* main loop */
static void handle_audio(struct decoder_state *st);
static void detect_tone(struct decoder_state *st);
static int silent_signal(struct decoder_state *st);
static void select_low_tone(struct decoder_state *st);
/* separate tone tolerances */
static void select_separator_tone(struct decoder_state *st);
static int valid_signal(struct decoder_state *st);
static int is_valid_signal(struct decoder_state *st);
/* output to terminal */
static int set_ascii_bit(struct decoder_state *st);
static void print_char(struct decoder_state *st);
static void reset_char(struct decoder_state *st);
/* process samples/frames */
static void decode_pulse(struct decoder_state *st);
static signed short read_sample(struct decoder_state *st);
static void read_words(struct decoder_state *st);
static int set_ascii_bit(struct decoder_state *st);
static void print_char(struct decoder_state *st);
static void print_stats(struct decoder_state *st);
static void reset_char(struct decoder_state *st);
/* continually adjust tone */
static void detect_tone(struct decoder_state *st);
static int silent_signal(struct decoder_state *st);
static void select_low_tone(struct decoder_state *st);
/* debug */
static void print_stats(struct decoder_state *st);
/* error handling / usage */
static void err(int errval, const char *msg, ...);
static void usage(void);
static const char *progname(void);
/* portability (old systems) */
int getopt(int, char * const *, const char *);
extern char *optarg;
extern int optind;
@@ -321,70 +340,6 @@ handle_audio(struct decoder_state *st)
detect_tone(st);
}
/*
* Automatically detect spkmodem tone
*/
static void
detect_tone(struct decoder_state *st)
{
if (st->learn_frames >= LEARN_FRAMES)
return;
st->learn_frames++;
if (silent_signal(st))
return;
select_low_tone(st);
if (st->learn_frames != LEARN_FRAMES)
return;
st->freq_threshold =
(st->freq_min + st->freq_max) / 2;
if (st->debug)
printf("auto threshold: %dHz\n",
st->freq_threshold * FRAME_RATE);
}
/*
* Ignore silence / near silence.
* Both FIR windows will be near zero when no signal exists.
*/
static int
silent_signal(struct decoder_state *st)
{
return (st->freq_data <= 2 &&
st->freq_separator <= 2);
}
/*
* Choose the lowest active tone.
* Separator frames carry tone in the separator window,
* data frames carry tone in the data window.
*/
static void
select_low_tone(struct decoder_state *st)
{
int f;
f = st->freq_data;
if (f <= 0 || (st->freq_separator > 0 &&
st->freq_separator < f))
f = st->freq_separator;
if (f <= 0)
return;
if (f < st->freq_min)
st->freq_min = f;
if (f > st->freq_max)
st->freq_max = f;
}
/*
* collect separator tone statistics
* (and auto-adjust tolerances)
@@ -394,7 +349,7 @@ select_separator_tone(struct decoder_state *st)
{
int avg;
if (valid_signal(st))
if (is_valid_signal(st))
return;
if (st->sep_samples >= 50 && st->freq_separator <= 0)
@@ -422,12 +377,46 @@ select_separator_tone(struct decoder_state *st)
* from being misinterpreted as data.
*/
static int
valid_signal(struct decoder_state *st)
is_valid_signal(struct decoder_state *st)
{
return (st->freq_separator > 0 &&
st->freq_data > 0);
}
/*
* Each validated frame contributes one bit of modem data.
* Bits are accumulated MSB-first into the ASCII byte.
*/
static int
set_ascii_bit(struct decoder_state *st)
{
if (st->debug)
print_stats(st);
if (st->freq_data < st->freq_threshold)
st->ascii |= (1 << st->ascii_bit);
st->ascii_bit--;
return st->ascii_bit;
}
static void
print_char(struct decoder_state *st)
{
if (st->debug)
printf("<%c,%x>", st->ascii, st->ascii);
else
putchar(st->ascii);
reset_char(st);
}
static void
reset_char(struct decoder_state *st)
{
st->ascii = 0;
st->ascii_bit = 7;
}
/*
* Main demodulation step (moving-sum FIR filter).
*/
@@ -551,30 +540,67 @@ read_words(struct decoder_state *st)
}
/*
* Each validated frame contributes one bit of modem data.
* Bits are accumulated MSB-first into the ASCII byte.
* Automatically detect spkmodem tone
*/
static int
set_ascii_bit(struct decoder_state *st)
static void
detect_tone(struct decoder_state *st)
{
if (st->debug)
print_stats(st);
if (st->freq_data < st->freq_threshold)
st->ascii |= (1 << st->ascii_bit);
if (st->learn_frames >= LEARN_FRAMES)
return;
st->ascii_bit--;
return st->ascii_bit;
st->learn_frames++;
if (silent_signal(st))
return;
select_low_tone(st);
if (st->learn_frames != LEARN_FRAMES)
return;
st->freq_threshold =
(st->freq_min + st->freq_max) / 2;
if (st->debug)
printf("auto threshold: %dHz\n",
st->freq_threshold * FRAME_RATE);
}
static void
print_char(struct decoder_state *st)
/*
* Ignore silence / near silence.
* Both FIR windows will be near zero when no signal exists.
*/
static int
silent_signal(struct decoder_state *st)
{
if (st->debug)
printf("<%c,%x>", st->ascii, st->ascii);
else
putchar(st->ascii);
return (st->freq_data <= 2 &&
st->freq_separator <= 2);
}
reset_char(st);
/*
* Choose the lowest active tone.
* Separator frames carry tone in the separator window,
* data frames carry tone in the data window.
*/
static void
select_low_tone(struct decoder_state *st)
{
int f;
f = st->freq_data;
if (f <= 0 || (st->freq_separator > 0 &&
st->freq_separator < f))
f = st->freq_separator;
if (f <= 0)
return;
if (f < st->freq_min)
st->freq_min = f;
if (f > st->freq_max)
st->freq_max = f;
}
static void
@@ -610,13 +636,6 @@ print_stats(struct decoder_state *st)
sep_hz_max);
}
static void
reset_char(struct decoder_state *st)
{
st->ascii = 0;
st->ascii_bit = 7;
}
static void
err(int errval, const char *msg, ...)
{