lavfi/anullsrc: switch to an AVOptions-based system.

doc/filters.texi

@@ -1596,16 +1596,10 @@ as a template and to be employed in analysis / debugging tools, or as
 the source for filters which ignore the input data (for example the sox
 synth filter).
 
-It accepts an optional sequence of @var{key}=@var{value} pairs,
-separated by ":".
-
-The description of the accepted options follows.
+This source accepts the following options:
 
 @table @option
 
-@item sample_rate, s
-Specify the sample rate, and defaults to 44100.
-
 @item channel_layout, cl
 
 Specify the channel layout, and can be either an integer or a string
@@ -1616,6 +1610,9 @@ Check the channel_layout_map definition in
 @file{libavutil/channel_layout.c} for the mapping between strings and
 channel layout values.
 
+@item sample_rate, r
+Specify the sample rate, and defaults to 44100.
+
 @item nb_samples, n
 Set the number of samples per requested frames.
 

libavfilter/asrc_anullsrc.c

@@ -64,12 +64,6 @@ static int init(AVFilterContext *ctx, const char *args)
     ANullContext *null = ctx->priv;
     int ret;
 
-    null->class = &anullsrc_class;
-    av_opt_set_defaults(null);
-
-    if ((ret = av_set_options_string(null, args, "=", ":")) < 0)
-        return ret;
-
     if ((ret = ff_parse_sample_rate(&null->sample_rate,
                                      null->sample_rate_str, ctx)) < 0)
         return ret;

libavfilter/avfilter.c

@@ -676,7 +676,6 @@ static const char *const filters_left_to_update[] = {
     "aconvert",
     "aevalsrc",
     "amerge",
-    "anullsrc",
     "aresample",
     "asetnsamples",
     "atempo",