From: George Boyle <geo...@spotify.com>
For the blue and violet noise, I took the pink and brown noise
respectively and subtracted the offsets instead of adding them. When I
eyeball the frequency spectrum of the resulting outputs it looks correct
to me, i.e. the blue graph appears to be a mirror image of the pink, and
the same can be said of the violet and the brown. I did not do anything
else to confirm the correctness.
---
doc/filters.texi | 4 ++--
libavfilter/asrc_anoisesrc.c | 41 +++++++++++++++++++++++++++++++++++------
2 files changed, 37 insertions(+), 8 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index 2708fdb1df..dd88636bb9 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -4471,8 +4471,8 @@ Specify the duration of the generated audio stream. Not
specifying this option
results in noise with an infinite length.
@item color, colour, c
-Specify the color of noise. Available noise colors are white, pink, and brown.
-Default color is white.
+Specify the color of noise. Available noise colors are white, pink, brown,
+blue and violet. Default color is white.
@item seed, s
Specify a value used to seed the PRNG.
diff --git a/libavfilter/asrc_anoisesrc.c b/libavfilter/asrc_anoisesrc.c
index be0d5ab6a5..b60fdfe331 100644
--- a/libavfilter/asrc_anoisesrc.c
+++ b/libavfilter/asrc_anoisesrc.c
@@ -51,12 +51,14 @@ static const AVOption anoisesrc_options[] = {
{ "a", "set amplitude", OFFSET(amplitude),
AV_OPT_TYPE_DOUBLE, {.dbl = 1.}, 0., 1., FLAGS },
{ "duration", "set duration", OFFSET(duration),
AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, FLAGS },
{ "d", "set duration", OFFSET(duration),
AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, FLAGS },
- { "color", "set noise color", OFFSET(color),
AV_OPT_TYPE_INT, {.i64 = 1}, 0, 2, FLAGS, "color" },
- { "colour", "set noise color", OFFSET(color),
AV_OPT_TYPE_INT, {.i64 = 1}, 0, 2, FLAGS, "color" },
- { "c", "set noise color", OFFSET(color),
AV_OPT_TYPE_INT, {.i64 = 0}, 0, 2, FLAGS, "color" },
+ { "color", "set noise color", OFFSET(color),
AV_OPT_TYPE_INT, {.i64 = 1}, 0, 4, FLAGS, "color" },
+ { "colour", "set noise color", OFFSET(color),
AV_OPT_TYPE_INT, {.i64 = 1}, 0, 4, FLAGS, "color" },
+ { "c", "set noise color", OFFSET(color),
AV_OPT_TYPE_INT, {.i64 = 0}, 0, 4, FLAGS, "color" },
{ "white", 0, 0,
AV_OPT_TYPE_CONST, {.i64 = 0}, 0, 0, FLAGS, "color" },
{ "pink", 0, 0,
AV_OPT_TYPE_CONST, {.i64 = 1}, 0, 0, FLAGS, "color" },
{ "brown", 0, 0,
AV_OPT_TYPE_CONST, {.i64 = 2}, 0, 0, FLAGS, "color" },
+ { "blue", 0, 0,
AV_OPT_TYPE_CONST, {.i64 = 3}, 0, 0, FLAGS, "color" },
+ { "violet", 0, 0,
AV_OPT_TYPE_CONST, {.i64 = 4}, 0, 0, FLAGS, "color" },
{ "seed", "set random seed", OFFSET(seed),
AV_OPT_TYPE_INT64, {.i64 = -1}, -1, UINT_MAX, FLAGS },
{ "s", "set random seed", OFFSET(seed),
AV_OPT_TYPE_INT64, {.i64 = -1}, -1, UINT_MAX, FLAGS },
{ "nb_samples", "set the number of samples per requested frame",
OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 1, INT_MAX, FLAGS },
@@ -121,6 +123,22 @@ static double pink_filter(double white, double *buf)
return pink * 0.11;
}
+static double blue_filter(double white, double *buf)
+{
+ double blue;
+
+ /* Same as pink_filter but subtract the offsets rather than add */
+ buf[0] = 0.0555179 * white - 0.99886 * buf[0];
+ buf[1] = 0.0750759 * white - 0.99332 * buf[1];
+ buf[2] = 0.1538520 * white - 0.96900 * buf[2];
+ buf[3] = 0.3104856 * white - 0.86650 * buf[3];
+ buf[4] = 0.5329522 * white - 0.55000 * buf[4];
+ buf[5] = -0.016898 * white + 0.76160 * buf[5];
+ blue = buf[0] + buf[1] + buf[2] + buf[3] + buf[4] + buf[5] + buf[6] +
white * 0.5362;
+ buf[6] = white * 0.115926;
+ return blue * 0.11;
+}
+
static double brown_filter(double white, double *buf)
{
double brown;
@@ -130,6 +148,15 @@ static double brown_filter(double white, double *buf)
return brown * 3.5;
}
+static double violet_filter(double white, double *buf)
+{
+ double violet;
+
+ violet = ((0.02 * white) - buf[0]) / 1.02;
+ buf[0] = violet;
+ return violet * 3.5;
+}
+
static av_cold int config_props(AVFilterLink *outlink)
{
AVFilterContext *ctx = outlink->src;
@@ -144,9 +171,11 @@ static av_cold int config_props(AVFilterLink *outlink)
s->duration = av_rescale(s->duration, s->sample_rate, AV_TIME_BASE);
switch (s->color) {
- case 0: s->filter = white_filter; break;
- case 1: s->filter = pink_filter; break;
- case 2: s->filter = brown_filter; break;
+ case 0: s->filter = white_filter; break;
+ case 1: s->filter = pink_filter; break;
+ case 2: s->filter = brown_filter; break;
+ case 3: s->filter = blue_filter; break;
+ case 4: s->filter = violet_filter; break;
}
return 0;
--
2.13.3
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