From: Martin Guy <martinw...@gmail.com>
This change adds a "normalize" flag, -n, to sox spectrogram to adjust
the spectrogram gain such that the highest values get the brightest
colours, allowing one to get uniform spectrograms regardless of
different volumes in music files.
Tested-by: Eric Wong <normalper...@yhbt.net>
---
sox.1 | 4 ++++
src/spectrogram.c | 23 ++++++++++++++++++++---
2 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/sox.1 b/sox.1
index 5a4766dd..04ab09b1 100644
--- a/sox.1
+++ b/sox.1
@@ -3235,6 +3235,10 @@ A negative
.I num
effectively increases the `brightness' of the spectrogram display,
and vice versa.
+.IP \fB\-n\fR
+Sets the upper limit of the Z axis so that the loudest pixels
+are shown using the brightest colour in the palette - a kind of
+automatic \fB\-Z\fR flag.
.IP \fB\-q\ \fInum\fR
Sets the Z-axis quantisation, i.e. the number of different colours (or
intensities) in which to render Z-axis
diff --git a/src/spectrogram.c b/src/spectrogram.c
index b38d2124..34457f21 100644
--- a/src/spectrogram.c
+++ b/src/spectrogram.c
@@ -59,7 +59,7 @@ typedef struct {
double pixels_per_sec, window_adjust;
int x_size0, y_size, Y_size, dB_range, gain, spectrum_points, perm;
sox_bool monochrome, light_background, high_colour, slack_overlap, no_axes;
- sox_bool raw, alt_palette, truncate;
+ sox_bool normalize, raw, alt_palette, truncate;
win_type_t win_type;
char const * out_name, * title, * comment;
char const *duration_str, *start_time_str;
@@ -113,7 +113,7 @@ static int getopts(sox_effect_t * effp, int argc, char
**argv)
char const * next;
int c;
lsx_getopt_t optstate;
- lsx_getopt_init(argc, argv, "+S:d:x:X:y:Y:z:Z:q:p:W:w:st:c:AarmlhTo:", NULL,
lsx_getopt_flag_none, 1, &optstate);
+ lsx_getopt_init(argc, argv, "+S:d:x:X:y:Y:z:Z:q:p:W:w:st:c:AarmnlhTo:",
NULL, lsx_getopt_flag_none, 1, &optstate);
p->dB_range = 120, p->spectrum_points = 249, p->perm = 1; /* Non-0 defaults
*/
p->out_name = "spectrogram.png", p->comment = "Created by SoX";
@@ -134,6 +134,7 @@ static int getopts(sox_effect_t * effp, int argc, char
**argv)
case 'a': p->no_axes = sox_true; break;
case 'r': p->raw = sox_true; break;
case 'm': p->monochrome = sox_true; break;
+ case 'n': p->normalize = sox_true; break;
case 'l': p->light_background = sox_true; break;
case 'h': p->high_colour = sox_true; break;
case 'T': p->truncate = sox_true; break;
@@ -557,6 +558,7 @@ static int stop(sox_effect_t * effp) /* only called, by
end(), on flow 0 */
int i, j, k, base, step, tick_len = 3 - p->no_axes;
char text[200], * prefix;
double limit;
+ float autogain = 0.0; /* Is changed if the -n flag was supplied */
free(p->shared);
if (p->using_stdout) {
@@ -583,8 +585,22 @@ static int stop(sox_effect_t * effp) /* only called, by
end(), on flow 0 */
png_rows[rows - 1 - j] = (png_bytep)(pixels + j * cols);
/* Spectrogram */
+
+ if (p->normalize)
+ /* values are already in dB, so we subtract the maximum value
+ * (which will normally be negative) to raise the maximum to 0.0.
+ */
+ autogain = -p->max;
+
for (k = 0; k < chans; ++k) {
priv_t * q = (priv_t *)(effp - effp->flow + k)->priv;
+
+ if (p->normalize) {
+ float *fp;
+
+ for (i = p->rows * p->cols, fp = q->dBfs; i > 0 ; fp++, i--)
+ *fp += autogain;
+ }
base = !p->raw * below + (chans - 1 - k) * (p->rows + 1);
for (j = 0; j < p->rows; ++j) {
for (i = 0; i < p->cols; ++i)
@@ -651,7 +667,7 @@ static int stop(sox_effect_t * effp) /* only called, by
end(), on flow 0 */
step = 10 * ceil(p->dB_range / 10. * (font_y + 2) / (k - 1));
for (i = 0; i <= p->dB_range; i += step) { /* (Tick) labels */
int y = (double)i / p->dB_range * (k - 1) + .5;
- sprintf(text, "%+i", i - p->gain - p->dB_range);
+ sprintf(text, "%+i", i - p->gain - p->dB_range - (int)(autogain+0.5));
print_at(cols - right + 1, base + y + 5, Labels, text);
}
}
@@ -692,6 +708,7 @@ sox_effect_handler_t const * lsx_spectrogram_effect_fn(void)
"\t-Y num\tY-height total (i.e. not per channel); default 550",
"\t-z num\tZ-axis range in dB; default 120",
"\t-Z num\tZ-axis maximum in dBFS; default 0",
+ "\t-n\tSet Z-axis maximum to the brightest pixel",
"\t-q num\tZ-axis quantisation (0 - 249); default 249",
"\t-w name\tWindow:
Hann(default)/Hamming/Bartlett/Rectangular/Kaiser/Dolph",
"\t-W num\tWindow adjust parameter (-10 - 10); applies only to
Kaiser/Dolph",
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