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avfilter/avf_showspectrum: add option to control dynamic range for colors

This commit is contained in:
Paul B Mahol 2021-08-05 20:57:23 +02:00
parent 2146b65553
commit 2678b4f81b
2 changed files with 18 additions and 3 deletions
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8
doc/filters.texi
View File

@ -26914,6 +26914,10 @@ Set upper frame rate limit. Default is @code{auto}, unlimited.
@item legend
Draw time and frequency axes and legends. Default is disabled.
@item drange
Set dynamic range used to calculate intensity color values. Default is 120dBFS.
Allowed range is from 10 to 200.
@end table
The usage is very similar to the showwaves filter; see the examples in that
@ -27087,6 +27091,10 @@ Set start frequency from which to display spectrogram. Default is @code{0}.
@item stop
Set stop frequency to which to display spectrogram. Default is @code{0}.
@item drange
Set dynamic range used to calculate intensity color values. Default is 120dBFS.
Allowed range is from 10 to 200.
@end table
@subsection Examples

13
libavfilter/avf_showspectrum.c
View File

@ -101,6 +101,8 @@ typedef struct ShowSpectrumContext {
int single_pic;
int legend;
int start_x, start_y;
float drange;
float dmin, dscale;
int (*plot_channel)(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs);
} ShowSpectrumContext;
@ -181,6 +183,7 @@ static const AVOption showspectrum_options[] = {
{ "stop", "stop frequency", OFFSET(stop), AV_OPT_TYPE_INT, {.i64 = 0}, 0, INT32_MAX, FLAGS },
{ "fps", "set video rate", OFFSET(rate_str), AV_OPT_TYPE_STRING, {.str = "auto"}, 0, 0, FLAGS },
{ "legend", "draw legend", OFFSET(legend), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, FLAGS },
{ "drange", "set dynamic range in dBFS", OFFSET(drange), AV_OPT_TYPE_FLOAT, {.dbl = 120}, 10, 200, FLAGS },
{ NULL }
};
@ -871,10 +874,10 @@ static int draw_legend(AVFilterContext *ctx, int samples)
}
for (y = 0; ch == 0 && y < h; y += h / 10) {
float value = 120.f * log10f(1.f - y / (float)h);
float value = s->drange * log10f(1.f - y / (float)h);
char *text;
if (value < -120)
if (value < -s->drange)
break;
text = av_asprintf("%.0f dB", value);
if (!text)
@ -925,7 +928,7 @@ static float get_value(AVFilterContext *ctx, int ch, int y)
a = av_clipf(powf(a, 0.20), 0, 1);
break;
case LOG:
a = 1.f + log10f(av_clipf(a, 1e-6, 1)) / 6.f; // zero = -120dBFS
a = 1.f + log10f(av_clipf(a, s->dmin, 1.f)) * s->dscale;
break;
default:
av_assert0(0);
@ -999,6 +1002,9 @@ static int config_output(AVFilterLink *outlink)
int i, fft_size, h, w, ret;
float overlap;
s->dmin = expf(-s->drange * M_LN10 / 20.f);
s->dscale = -1.f / log10f(s->dmin);
switch (s->fscale) {
case F_LINEAR: s->plot_channel = plot_channel_lin; break;
case F_LOG: s->plot_channel = plot_channel_log; break;
@ -1641,6 +1647,7 @@ static const AVOption showspectrumpic_options[] = {
{ "rotation", "color rotation", OFFSET(rotation), AV_OPT_TYPE_FLOAT, {.dbl = 0}, -1, 1, FLAGS },
{ "start", "start frequency", OFFSET(start), AV_OPT_TYPE_INT, {.i64 = 0}, 0, INT32_MAX, FLAGS },
{ "stop", "stop frequency", OFFSET(stop), AV_OPT_TYPE_INT, {.i64 = 0}, 0, INT32_MAX, FLAGS },
{ "drange", "set dynamic range in dBFS", OFFSET(drange), AV_OPT_TYPE_FLOAT, {.dbl = 120}, 10, 200, FLAGS },
{ NULL }
};