avfilter/af_silenceremove: make size of window user configurable

Signed-off-by: Paul B Mahol <onemda@gmail.com>

doc/filters.texi

@@ -2973,6 +2973,10 @@ to remove the pauses completely. Default value is @code{0}.
 Set how is silence detected. Can be @code{rms} or @code{peak}. Second is faster
 and works better with digital silence which is exactly 0.
 Default value is @code{rms}.
+
+@item window
+Set ratio used to calculate size of window for detecting silence.
+Default value is @code{0.02}. Allowed range is from @code{0} to @code{10}.
 @end table
 
 @subsection Examples

libavfilter/af_silenceremove.c

@@ -61,6 +61,7 @@ typedef struct SilenceRemoveContext {
     size_t stop_holdoff_end;
     int    stop_found_periods;
 
+    double window_ratio;
     double *window;
     double *window_current;
     double *window_end;
@@ -89,6 +90,7 @@ static const AVOption silenceremove_options[] = {
     { "detection",       NULL, OFFSET(detection),       AV_OPT_TYPE_INT,      {.i64=1},     0,       1, FLAGS, "detection" },
     {   "peak",          0,    0,                       AV_OPT_TYPE_CONST,    {.i64=0},     0,       0, FLAGS, "detection" },
     {   "rms",           0,    0,                       AV_OPT_TYPE_CONST,    {.i64=1},     0,       0, FLAGS, "detection" },
+    { "window",          NULL, OFFSET(window_ratio),    AV_OPT_TYPE_DOUBLE,   {.dbl=0.02},  0,      10, FLAGS },
     { NULL }
 };
 
@@ -175,7 +177,7 @@ static int config_input(AVFilterLink *inlink)
     AVFilterContext *ctx = inlink->dst;
     SilenceRemoveContext *s = ctx->priv;
 
-    s->window_size = (inlink->sample_rate / 50) * inlink->channels;
+    s->window_size = FFMAX((inlink->sample_rate * s->window_ratio), 1) * inlink->channels;
     s->window = av_malloc_array(s->window_size, sizeof(*s->window));
     if (!s->window)
         return AVERROR(ENOMEM);