ffmpeg: let AVFilterGraph parse the filter_threads option

This way the CLI accepts for "filter_threads" the same values as for the
libavcodec specific option "threads".

Fixes FATE with THREADS=auto which was broken in bdc1bdf3f5.

Signed-off-by: James Almer <jamrial@gmail.com>

fftools/ffmpeg.c

@@ -653,6 +653,7 @@ static void ffmpeg_cleanup(int ret)
                    av_err2str(AVERROR(errno)));
     }
     av_freep(&vstats_filename);
+    av_freep(&filter_nbthreads);
 
     av_freep(&input_streams);
     av_freep(&input_files);

fftools/ffmpeg.h

@@ -629,7 +629,7 @@ extern AVIOContext *progress_avio;
 extern float max_error_rate;
 extern char *videotoolbox_pixfmt;
 
-extern int filter_nbthreads;
+extern char *filter_nbthreads;
 extern int filter_complex_nbthreads;
 extern int vstats_version;
 extern int auto_conversion_filters;

fftools/ffmpeg_filter.c

@@ -968,8 +968,11 @@ int configure_filtergraph(FilterGraph *fg)
         char args[512];
         AVDictionaryEntry *e = NULL;
 
-        fg->graph->nb_threads = filter_nbthreads;
-        if (!fg->graph->nb_threads) {
+        if (filter_nbthreads) {
+            ret = av_opt_set(fg->graph, "threads", filter_nbthreads, 0);
+            if (ret < 0)
+                goto fail;
+        } else {
             e = av_dict_get(ost->encoder_opts, "threads", NULL, 0);
             if (e)
                 av_opt_set(fg->graph, "threads", e->value, 0);

fftools/ffmpeg_opt.c

@@ -169,7 +169,7 @@ int qp_hist           = 0;
 int stdin_interaction = 1;
 int frame_bits_per_raw_sample = 0;
 float max_error_rate  = 2.0/3;
-int filter_nbthreads = 0;
+char *filter_nbthreads;
 int filter_complex_nbthreads = 0;
 int vstats_version = 2;
 int auto_conversion_filters = 1;
@@ -264,6 +264,13 @@ static AVDictionary *strip_specifiers(AVDictionary *dict)
     return ret;
 }
 
+static int opt_filter_threads(void *optctx, const char *opt, const char *arg)
+{
+    av_free(filter_nbthreads);
+    filter_nbthreads = av_strdup(arg);
+    return 0;
+}
+
 static int opt_abort_on(void *optctx, const char *opt, const char *arg)
 {
     static const AVOption opts[] = {
@@ -3618,7 +3625,7 @@ const OptionDef options[] = {
         "set profile", "profile" },
     { "filter",         HAS_ARG | OPT_STRING | OPT_SPEC | OPT_OUTPUT, { .off = OFFSET(filters) },
         "set stream filtergraph", "filter_graph" },
-    { "filter_threads",  HAS_ARG | OPT_INT,                          { &filter_nbthreads },
+    { "filter_threads", HAS_ARG,                                     { .func_arg = opt_filter_threads },
         "number of non-complex filter threads" },
     { "filter_script",  HAS_ARG | OPT_STRING | OPT_SPEC | OPT_OUTPUT, { .off = OFFSET(filter_scripts) },
         "read stream filtergraph description from a file", "filename" },