[FFmpeg-cvslog] avfilter/af_crossfeed: add option for linear phase filtering
Paul B Mahol
git at videolan.org
Mon May 9 23:21:22 EEST 2022
ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Mon May 9 21:59:03 2022 +0200| [5ccd8f492bc807dbf084bf13f3f288b2f4ac41f1] | committer: Paul B Mahol
avfilter/af_crossfeed: add option for linear phase filtering
But at expense of additional delay.
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=5ccd8f492bc807dbf084bf13f3f288b2f4ac41f1
---
doc/filters.texi | 7 ++
libavfilter/af_crossfeed.c | 174 +++++++++++++++++++++++++++++++++++++++++----
2 files changed, 167 insertions(+), 14 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index 468c277798..22a88d7f58 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -4205,6 +4205,13 @@ Set input gain. Default is 0.9.
@item level_out
Set output gain. Default is 1.
+
+ at item block_size
+Set block size used for reverse IIR processing. If this value is set to high enough
+value (higher than impulse response length truncated when reaches near zero values) filtering
+will become linear phase otherwise if not big enough it will just produce nasty artifacts.
+
+Note that filter delay will be exactly this many samples when set to non-zero value.
@end table
@subsection Commands
diff --git a/libavfilter/af_crossfeed.c b/libavfilter/af_crossfeed.c
index 15990703e1..d7110098e0 100644
--- a/libavfilter/af_crossfeed.c
+++ b/libavfilter/af_crossfeed.c
@@ -21,6 +21,7 @@
#include "libavutil/opt.h"
#include "avfilter.h"
#include "audio.h"
+#include "filters.h"
#include "formats.h"
typedef struct CrossfeedContext {
@@ -31,11 +32,16 @@ typedef struct CrossfeedContext {
double slope;
double level_in;
double level_out;
+ int block_samples;
+ int block_size;
double a0, a1, a2;
double b0, b1, b2;
double w1, w2;
+
+ double *mid;
+ double *side[3];
} CrossfeedContext;
static int query_formats(AVFilterContext *ctx)
@@ -77,9 +83,49 @@ static int config_input(AVFilterLink *inlink)
s->b1 /= s->a0;
s->b2 /= s->a0;
+ if (s->block_samples == 0 && s->block_size > 0) {
+ s->block_samples = s->block_size;
+ s->mid = av_calloc(s->block_samples * 2, sizeof(*s->mid));
+ for (int i = 0; i < 3; i++) {
+ s->side[i] = av_calloc(s->block_samples * 2, sizeof(*s->side[0]));
+ if (!s->side[i])
+ return AVERROR(ENOMEM);
+ }
+ }
+
return 0;
}
+static void reverse_samples(double *dst, const double *src,
+ int nb_samples)
+{
+ for (int i = 0, j = nb_samples - 1; i < nb_samples; i++, j--)
+ dst[i] = src[j];
+}
+
+static void filter_samples(double *dst, const double *src,
+ int nb_samples,
+ double b0, double b1, double b2,
+ double a1, double a2,
+ double *sw1, double *sw2)
+{
+ double w1 = *sw1;
+ double w2 = *sw2;
+
+ for (int n = 0; n < nb_samples; n++) {
+ double side = src[n];
+ double oside = side * b0 + w1;
+
+ w1 = b1 * side + w2 + a1 * oside;
+ w2 = b2 * side + a2 * oside;
+
+ dst[n] = oside;
+ }
+
+ *sw1 = w1;
+ *sw2 = w2;
+}
+
static int filter_frame(AVFilterLink *inlink, AVFrame *in)
{
AVFilterContext *ctx = inlink->dst;
@@ -95,7 +141,6 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
const double a2 = -s->a2;
AVFrame *out;
double *dst;
- int n;
if (av_frame_is_writable(in)) {
out = in;
@@ -109,21 +154,79 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
}
dst = (double *)out->data[0];
- for (n = 0; n < out->nb_samples; n++, src += 2, dst += 2) {
- double mid = (src[0] + src[1]) * level_in * .5;
- double side = (src[0] - src[1]) * level_in * .5;
- double oside = side * b0 + s->w1;
+ if (s->block_samples == 0) {
+ double w1 = s->w1;
+ double w2 = s->w2;
+
+ for (int n = 0; n < out->nb_samples; n++, src += 2, dst += 2) {
+ double mid = (src[0] + src[1]) * level_in * .5;
+ double side = (src[0] - src[1]) * level_in * .5;
+ double oside = side * b0 + w1;
+
+ w1 = b1 * side + w2 + a1 * oside;
+ w2 = b2 * side + a2 * oside;
+
+ if (ctx->is_disabled) {
+ dst[0] = src[0];
+ dst[1] = src[1];
+ } else {
+ dst[0] = (mid + oside) * level_out;
+ dst[1] = (mid - oside) * level_out;
+ }
+ }
+
+ s->w1 = w1;
+ s->w2 = w2;
+ } else {
+ double *mdst = s->mid + s->block_samples;
+ double *sdst = s->side[0] + s->block_samples;
+ double *ssrc = s->side[0];
+ double *msrc = s->mid;
+ double w1 = s->w1;
+ double w2 = s->w2;
+
+ for (int n = 0; n < out->nb_samples; n++, src += 2) {
+ mdst[n] = (src[0] + src[1]) * level_in * .5;
+ sdst[n] = (src[0] - src[1]) * level_in * .5;
+ }
+
+ sdst = s->side[1];
+ filter_samples(sdst, ssrc, s->block_samples,
+ b0, b1, b2, a1, a2,
+ &w1, &w2);
+ s->w1 = w1;
+ s->w2 = w2;
- s->w1 = b1 * side + s->w2 + a1 * oside;
- s->w2 = b2 * side + a2 * oside;
+ ssrc = s->side[0] + s->block_samples;
+ sdst = s->side[1] + s->block_samples;
+ filter_samples(sdst, ssrc, s->block_samples,
+ b0, b1, b2, a1, a2,
+ &w1, &w2);
- if (ctx->is_disabled) {
- dst[0] = src[0];
- dst[1] = src[1];
- } else {
- dst[0] = (mid + oside) * level_out;
- dst[1] = (mid - oside) * level_out;
+ reverse_samples(s->side[2], s->side[1], s->block_samples * 2);
+ w1 = w2 = 0.;
+ filter_samples(s->side[2], s->side[2], s->block_samples * 2,
+ b0, b1, b2, a1, a2,
+ &w1, &w2);
+
+ reverse_samples(s->side[1], s->side[2] + s->block_samples, s->block_samples);
+
+ src = (const double *)in->data[0];
+ ssrc = s->side[1];
+ for (int n = 0; n < out->nb_samples; n++, src += 2, dst += 2) {
+ if (ctx->is_disabled) {
+ dst[0] = src[0];
+ dst[1] = src[1];
+ } else {
+ dst[0] = (msrc[n] + ssrc[n]) * level_out;
+ dst[1] = (msrc[n] - ssrc[n]) * level_out;
+ }
}
+
+ memmove(s->mid, s->mid + s->block_samples,
+ s->block_samples * sizeof(*s->mid));
+ memmove(s->side[0], s->side[0] + s->block_samples,
+ s->block_samples * sizeof(*s->side[0]));
}
if (out != in)
@@ -131,6 +234,37 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
return ff_filter_frame(outlink, out);
}
+static int activate(AVFilterContext *ctx)
+{
+ AVFilterLink *inlink = ctx->inputs[0];
+ AVFilterLink *outlink = ctx->outputs[0];
+ CrossfeedContext *s = ctx->priv;
+ AVFrame *in = NULL;
+ int ret;
+
+ FF_FILTER_FORWARD_STATUS_BACK(outlink, inlink);
+
+ if (s->block_samples > 0) {
+ ret = ff_inlink_consume_samples(inlink, s->block_samples, s->block_samples, &in);
+ } else {
+ ret = ff_inlink_consume_frame(inlink, &in);
+ }
+ if (ret < 0)
+ return ret;
+ if (ret > 0)
+ return filter_frame(inlink, in);
+
+ if (s->block_samples > 0 && ff_inlink_queued_samples(inlink) >= s->block_samples) {
+ ff_filter_set_ready(ctx, 10);
+ return 0;
+ }
+
+ FF_FILTER_FORWARD_STATUS(inlink, outlink);
+ FF_FILTER_FORWARD_WANTED(outlink, inlink);
+
+ return FFERROR_NOT_READY;
+}
+
static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,
char *res, int res_len, int flags)
{
@@ -143,8 +277,18 @@ static int process_command(AVFilterContext *ctx, const char *cmd, const char *ar
return config_input(ctx->inputs[0]);
}
+static av_cold void uninit(AVFilterContext *ctx)
+{
+ CrossfeedContext *s = ctx->priv;
+
+ av_freep(&s->mid);
+ for (int i = 0; i < 3; i++)
+ av_freep(&s->side[i]);
+}
+
#define OFFSET(x) offsetof(CrossfeedContext, x)
#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
+#define AF AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
static const AVOption crossfeed_options[] = {
{ "strength", "set crossfeed strength", OFFSET(strength), AV_OPT_TYPE_DOUBLE, {.dbl=.2}, 0, 1, FLAGS },
@@ -152,6 +296,7 @@ static const AVOption crossfeed_options[] = {
{ "slope", "set curve slope", OFFSET(slope), AV_OPT_TYPE_DOUBLE, {.dbl=.5}, .01, 1, FLAGS },
{ "level_in", "set level in", OFFSET(level_in), AV_OPT_TYPE_DOUBLE, {.dbl=.9}, 0, 1, FLAGS },
{ "level_out", "set level out", OFFSET(level_out), AV_OPT_TYPE_DOUBLE, {.dbl=1.}, 0, 1, FLAGS },
+ { "block_size", "set the block size", OFFSET(block_size),AV_OPT_TYPE_INT, {.i64=0}, 0, 32768, AF },
{ NULL }
};
@@ -161,7 +306,6 @@ static const AVFilterPad inputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_AUDIO,
- .filter_frame = filter_frame,
.config_props = config_input,
},
};
@@ -178,6 +322,8 @@ const AVFilter ff_af_crossfeed = {
.description = NULL_IF_CONFIG_SMALL("Apply headphone crossfeed filter."),
.priv_size = sizeof(CrossfeedContext),
.priv_class = &crossfeed_class,
+ .activate = activate,
+ .uninit = uninit,
FILTER_INPUTS(inputs),
FILTER_OUTPUTS(outputs),
FILTER_QUERY_FUNC(query_formats),
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