[FFmpeg-devel] [PATCH] avfilter: add asubcut filter
Marton Balint
cus at passwd.hu
Mon Nov 30 15:58:25 EET 2020
On Mon, 30 Nov 2020, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
> doc/filters.texi | 25 +++++++++++
> libavfilter/Makefile | 1 +
> libavfilter/af_asupercut.c | 89 ++++++++++++++++++++++++++++++--------
> libavfilter/allfilters.c | 1 +
> 4 files changed, 97 insertions(+), 19 deletions(-)
>
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 06ed28f3f9..348cdae4e9 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -2636,6 +2636,28 @@ Default value is 20.
>
> This filter supports the all above options as @ref{commands}.
>
> + at section asubcut
> +Cut subwoofer frequencies.
Please explain in the documentation how is this different from a simple
highpass filter, and when it is preferable to use this and when to use
highpass.
Thanks,
Marton
> +
> +The filter accepts the following options:
> +
> + at table @option
> + at item cutoff
> +Set cutoff frequency in Hertz. Allowed range is 2 to 200.
> +Default value is 20.
> +
> + at item order
> +Set filter order. Available values are from 3 to 20.
> +Default value is 10.
> +
> + at item level
> +Set input gain level. Allowed range is from 0 to 1. Default value is 1.
> + at end table
> +
> + at subsection Commands
> +
> +This filter supports the all above options as @ref{commands}.
> +
> @section asupercut
> Cut super frequencies.
>
> @@ -2649,6 +2671,9 @@ Default value is 20000.
> @item order
> Set filter order. Available values are from 3 to 20.
> Default value is 10.
> +
> + at item level
> +Set input gain level. Allowed range is from 0 to 1. Default value is 1.
> @end table
>
> @subsection Commands
> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
> index cff9402989..03998dc064 100644
> --- a/libavfilter/Makefile
> +++ b/libavfilter/Makefile
> @@ -90,6 +90,7 @@ OBJS-$(CONFIG_ASR_FILTER) += af_asr.o
> OBJS-$(CONFIG_ASTATS_FILTER) += af_astats.o
> OBJS-$(CONFIG_ASTREAMSELECT_FILTER) += f_streamselect.o framesync.o
> OBJS-$(CONFIG_ASUBBOOST_FILTER) += af_asubboost.o
> +OBJS-$(CONFIG_ASUBCUT_FILTER) += af_asupercut.o
> OBJS-$(CONFIG_ASUPERCUT_FILTER) += af_asupercut.o
> OBJS-$(CONFIG_ATEMPO_FILTER) += af_atempo.o
> OBJS-$(CONFIG_ATRIM_FILTER) += trim.o
> diff --git a/libavfilter/af_asupercut.c b/libavfilter/af_asupercut.c
> index ef241405d8..6d0a2b79a9 100644
> --- a/libavfilter/af_asupercut.c
> +++ b/libavfilter/af_asupercut.c
> @@ -32,6 +32,7 @@ typedef struct ASuperCutContext {
> const AVClass *class;
>
> double cutoff;
> + double level;
> int order;
>
> int filter_count;
> @@ -95,27 +96,52 @@ static int get_coeffs(AVFilterContext *ctx)
> s->filter_count = s->order / 2 + (s->order & 1);
> calc_q_factors(s->order, q);
>
> - if (s->order & 1) {
> - BiquadCoeffs *coeffs = &s->coeffs[0];
> - double omega = 2. * tan(M_PI * w0);
> + if (!strcmp(ctx->filter->name, "asubcut")) {
> + if (s->order & 1) {
> + BiquadCoeffs *coeffs = &s->coeffs[0];
> + double omega = 2. * tan(M_PI * w0);
>
> - coeffs->b0 = omega / (2. + omega);
> - coeffs->b1 = coeffs->b0;
> - coeffs->b2 = 0.;
> - coeffs->a1 = -(omega - 2.) / (2. + omega);
> - coeffs->a2 = 0.;
> - }
> + coeffs->b0 = 2. / (2. + omega);
> + coeffs->b1 = -coeffs->b0;
> + coeffs->b2 = 0.;
> + coeffs->a1 = -(omega - 2.) / (2. + omega);
> + coeffs->a2 = 0.;
> + }
> +
> + for (int b = (s->order & 1); b < s->filter_count; b++) {
> + BiquadCoeffs *coeffs = &s->coeffs[b];
> + const int idx = b - (s->order & 1);
> + double norm = 1.0 / (1.0 + K / q[idx] + K * K);
>
> - for (int b = (s->order & 1); b < s->filter_count; b++) {
> - BiquadCoeffs *coeffs = &s->coeffs[b];
> - const int idx = b - (s->order & 1);
> - double norm = 1.0 / (1.0 + K / q[idx] + K * K);
> + coeffs->b0 = norm;
> + coeffs->b1 = -2.0 * coeffs->b0;
> + coeffs->b2 = coeffs->b0;
> + coeffs->a1 = -2.0 * (K * K - 1.0) * norm;
> + coeffs->a2 = -(1.0 - K / q[idx] + K * K) * norm;
> + }
> + } else {
> + if (s->order & 1) {
> + BiquadCoeffs *coeffs = &s->coeffs[0];
> + double omega = 2. * tan(M_PI * w0);
> +
> + coeffs->b0 = omega / (2. + omega);
> + coeffs->b1 = coeffs->b0;
> + coeffs->b2 = 0.;
> + coeffs->a1 = -(omega - 2.) / (2. + omega);
> + coeffs->a2 = 0.;
> + }
>
> - coeffs->b0 = K * K * norm;
> - coeffs->b1 = 2.0 * coeffs->b0;
> - coeffs->b2 = coeffs->b0;
> - coeffs->a1 = -2.0 * (K * K - 1.0) * norm;
> - coeffs->a2 = -(1.0 - K / q[idx] + K * K) * norm;
> + for (int b = (s->order & 1); b < s->filter_count; b++) {
> + BiquadCoeffs *coeffs = &s->coeffs[b];
> + const int idx = b - (s->order & 1);
> + double norm = 1.0 / (1.0 + K / q[idx] + K * K);
> +
> + coeffs->b0 = K * K * norm;
> + coeffs->b1 = 2.0 * coeffs->b0;
> + coeffs->b2 = coeffs->b0;
> + coeffs->a1 = -2.0 * (K * K - 1.0) * norm;
> + coeffs->a2 = -(1.0 - K / q[idx] + K * K) * norm;
> + }
> }
>
> return 0;
> @@ -135,6 +161,7 @@ static int filter_channels_## name(AVFilterContext *ctx, void *arg, \
> AVFrame *in = td->in; \
> const int start = (in->channels * jobnr) / nb_jobs; \
> const int end = (in->channels * (jobnr+1)) / nb_jobs; \
> + const double level = s->level; \
> \
> for (int ch = start; ch < end; ch++) { \
> const type *src = (const type *)in->extended_data[ch]; \
> @@ -150,7 +177,7 @@ static int filter_channels_## name(AVFilterContext *ctx, void *arg, \
> type *w = ((type *)s->w->extended_data[ch]) + b * 2; \
> \
> for (int n = 0; n < in->nb_samples; n++) { \
> - type sin = b ? dst[n] : src[n]; \
> + type sin = b ? dst[n] : src[n] * level; \
> type sout = sin * b0 + w[0]; \
> \
> w[0] = b1 * sin + w[1] + a1 * sout; \
> @@ -240,6 +267,7 @@ static av_cold void uninit(AVFilterContext *ctx)
> static const AVOption asupercut_options[] = {
> { "cutoff", "set cutoff frequency", OFFSET(cutoff), AV_OPT_TYPE_DOUBLE, {.dbl=20000}, 20000, 192000, FLAGS },
> { "order", "set filter order", OFFSET(order), AV_OPT_TYPE_INT, {.i64=10}, 3, 20, FLAGS },
> + { "level", "set input level", OFFSET(level), AV_OPT_TYPE_DOUBLE, {.dbl=1.}, 0., 1., FLAGS },
> { NULL }
> };
>
> @@ -276,3 +304,26 @@ AVFilter ff_af_asupercut = {
> .flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC |
> AVFILTER_FLAG_SLICE_THREADS,
> };
> +
> +static const AVOption asubcut_options[] = {
> + { "cutoff", "set cutoff frequency", OFFSET(cutoff), AV_OPT_TYPE_DOUBLE, {.dbl=20}, 2, 200, FLAGS },
> + { "order", "set filter order", OFFSET(order), AV_OPT_TYPE_INT, {.i64=10}, 3, 20, FLAGS },
> + { "level", "set input level", OFFSET(level), AV_OPT_TYPE_DOUBLE, {.dbl=1.}, 0., 1., FLAGS },
> + { NULL }
> +};
> +
> +AVFILTER_DEFINE_CLASS(asubcut);
> +
> +AVFilter ff_af_asubcut = {
> + .name = "asubcut",
> + .description = NULL_IF_CONFIG_SMALL("Cut subwoofer frequencies."),
> + .query_formats = query_formats,
> + .priv_size = sizeof(ASuperCutContext),
> + .priv_class = &asubcut_class,
> + .uninit = uninit,
> + .inputs = inputs,
> + .outputs = outputs,
> + .process_command = process_command,
> + .flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC |
> + AVFILTER_FLAG_SLICE_THREADS,
> +};
> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
> index 83f434bc27..d0fb7bfe9d 100644
> --- a/libavfilter/allfilters.c
> +++ b/libavfilter/allfilters.c
> @@ -83,6 +83,7 @@ extern AVFilter ff_af_asr;
> extern AVFilter ff_af_astats;
> extern AVFilter ff_af_astreamselect;
> extern AVFilter ff_af_asubboost;
> +extern AVFilter ff_af_asubcut;
> extern AVFilter ff_af_asupercut;
> extern AVFilter ff_af_atempo;
> extern AVFilter ff_af_atrim;
> --
> 2.17.1
>
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