lavfi/hue: add process_command callback

This allows dynamic reconfiguration of the filter.
The callback uses some code that was in the init function. Hence this code
has been moved in its own function.
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

doc/filters.texi

@@ -2350,6 +2350,18 @@ hue=PI/2:1
 @end example
 @end itemize
 
+@subsection Commands
+
+This filter supports the following command:
+@table @option
+@item reinit
+Modify the hue and/or the saturation of the input video.
+The command accepts the same named options and syntax than when calling the
+filter from the command-line.
+
+If a parameter is omitted, it is kept at its current value.
+@end table
+
 @section idet
 
 Interlaceing detect filter. This filter tries to detect if the input is

libavfilter/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  3
 #define LIBAVFILTER_VERSION_MINOR  15
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_hue.c

@@ -63,19 +63,19 @@ static const AVOption hue_options[] = {
 
 AVFILTER_DEFINE_CLASS(hue);
 
-static av_cold int init(AVFilterContext *ctx, const char *args)
+static inline int set_options(AVFilterContext *ctx, const char *args)
 {
     HueContext *hue = ctx->priv;
     int n, ret;
     char c1 = 0, c2 = 0;
     char *equal;
 
-    hue->class = &hue_class;
-    av_opt_set_defaults(hue);
-
     if (args) {
         /* named options syntax */
         if (equal = strchr(args, '=')) {
+            hue->hue     = -FLT_MAX;
+            hue->hue_deg = -FLT_MAX;
+
             if ((ret = av_set_options_string(hue, args, "=", ":")) < 0)
                 return ret;
             if (hue->hue != -FLT_MAX && hue->hue_deg != -FLT_MAX) {
@@ -103,6 +103,20 @@ static av_cold int init(AVFilterContext *ctx, const char *args)
         }
     }
 
+    return 0;
+}
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+    HueContext *hue = ctx->priv;
+    int ret;
+
+    hue->class = &hue_class;
+    av_opt_set_defaults(hue);
+
+    if ((ret = set_options(ctx, args)) < 0)
+        return ret;
+
     if (hue->saturation == -FLT_MAX)
         hue->hue = SAT_DEFAULT_VAL;
     if (hue->hue == -FLT_MAX)
@@ -223,6 +237,28 @@ static int draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
     return ff_draw_slice(inlink->dst->outputs[0], y, h, slice_dir);
 }
 
+static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,
+                           char *res, int res_len, int flags)
+{
+    HueContext *hue = ctx->priv;
+    int ret;
+
+    if (!strcmp(cmd, "reinit")) {
+        if ((ret = set_options(ctx, args)) < 0)
+            return ret;
+
+        if (hue->hue_deg != -FLT_MAX)
+            /* Convert angle from degrees to radians */
+            hue->hue = hue->hue_deg * M_PI / 180;
+
+        hue->hue_sin = rint(sin(hue->hue) * (1 << 16) * hue->saturation);
+        hue->hue_cos = rint(cos(hue->hue) * (1 << 16) * hue->saturation);
+    } else
+        return AVERROR(ENOSYS);
+
+    return 0;
+}
+
 AVFilter avfilter_vf_hue = {
     .name        = "hue",
     .description = NULL_IF_CONFIG_SMALL("Adjust the hue and saturation of the input video."),
@@ -232,6 +268,7 @@ AVFilter avfilter_vf_hue = {
     .init          = init,
     .uninit        = uninit,
     .query_formats = query_formats,
+    .process_command = process_command,
 
     .inputs = (const AVFilterPad[]) {
         {