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avfilter/af_acrossover: document roll-off of each filter order

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This commit is contained in:
Paul B Mahol 2020-12-02 12:28:01 +01:00
parent ba6e2a2d05
commit 0a5ff19643
2 changed files with 24 additions and 12 deletions
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14
doc/filters.texi
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@ -523,19 +523,31 @@ The filter accepts the following options:
Set split frequencies. Those must be positive and increasing.
@item order
Set filter order. Available values are:
Set filter order for each band split. This controls filter roll-off or steepness
of filter transfer function.
Available values are:
@table @samp
@item 2nd
12 dB per octave.
@item 4th
24 dB per octave.
@item 6th
36 dB per octave.
@item 8th
48 dB per octave.
@item 10th
60 dB per octave.
@item 12th
72 dB per octave.
@item 14th
84 dB per octave.
@item 16th
96 dB per octave.
@item 18th
108 dB per octave.
@item 20th
120 dB per octave.
@end table
Default is @var{4th}.

22
libavfilter/af_acrossover.c
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@ -83,17 +83,17 @@ typedef struct AudioCrossoverContext {
static const AVOption acrossover_options[] = {
{ "split", "set split frequencies", OFFSET(splits_str), AV_OPT_TYPE_STRING, {.str="500"}, 0, 0, AF },
{ "order", "set order", OFFSET(order_opt), AV_OPT_TYPE_INT, {.i64=1}, 0, 9, AF, "m" },
{ "2nd", "2nd order", 0, AV_OPT_TYPE_CONST, {.i64=0}, 0, 0, AF, "m" },
{ "4th", "4th order", 0, AV_OPT_TYPE_CONST, {.i64=1}, 0, 0, AF, "m" },
{ "6th", "6th order", 0, AV_OPT_TYPE_CONST, {.i64=2}, 0, 0, AF, "m" },
{ "8th", "8th order", 0, AV_OPT_TYPE_CONST, {.i64=3}, 0, 0, AF, "m" },
{ "10th", "10th order", 0, AV_OPT_TYPE_CONST, {.i64=4}, 0, 0, AF, "m" },
{ "12th", "12th order", 0, AV_OPT_TYPE_CONST, {.i64=5}, 0, 0, AF, "m" },
{ "14th", "14th order", 0, AV_OPT_TYPE_CONST, {.i64=6}, 0, 0, AF, "m" },
{ "16th", "16th order", 0, AV_OPT_TYPE_CONST, {.i64=7}, 0, 0, AF, "m" },
{ "18th", "18th order", 0, AV_OPT_TYPE_CONST, {.i64=8}, 0, 0, AF, "m" },
{ "20th", "20th order", 0, AV_OPT_TYPE_CONST, {.i64=9}, 0, 0, AF, "m" },
{ "order", "set filter order", OFFSET(order_opt), AV_OPT_TYPE_INT, {.i64=1}, 0, 9, AF, "m" },
{ "2nd", "2nd order (12 dB/8ve)", 0, AV_OPT_TYPE_CONST, {.i64=0}, 0, 0, AF, "m" },
{ "4th", "4th order (24 dB/8ve)", 0, AV_OPT_TYPE_CONST, {.i64=1}, 0, 0, AF, "m" },
{ "6th", "6th order (36 dB/8ve)", 0, AV_OPT_TYPE_CONST, {.i64=2}, 0, 0, AF, "m" },
{ "8th", "8th order (48 dB/8ve)", 0, AV_OPT_TYPE_CONST, {.i64=3}, 0, 0, AF, "m" },
{ "10th", "10th order (60 dB/8ve)",0, AV_OPT_TYPE_CONST, {.i64=4}, 0, 0, AF, "m" },
{ "12th", "12th order (72 dB/8ve)",0, AV_OPT_TYPE_CONST, {.i64=5}, 0, 0, AF, "m" },
{ "14th", "14th order (84 dB/8ve)",0, AV_OPT_TYPE_CONST, {.i64=6}, 0, 0, AF, "m" },
{ "16th", "16th order (96 dB/8ve)",0, AV_OPT_TYPE_CONST, {.i64=7}, 0, 0, AF, "m" },
{ "18th", "18th order (108 dB/8ve)",0, AV_OPT_TYPE_CONST, {.i64=8}, 0, 0, AF, "m" },
{ "20th", "20th order (120 dB/8ve)",0, AV_OPT_TYPE_CONST, {.i64=9}, 0, 0, AF, "m" },
{ "level", "set input gain", OFFSET(level_in), AV_OPT_TYPE_FLOAT, {.dbl=1}, 0, 1, AF },
{ NULL }
};