ffplay: add support for setting the number of filter threads

Signed-off-by: Marton Balint <cus@passwd.hu>

doc/ffplay.texi

@@ -195,6 +195,12 @@ input as soon as possible. Enabled by default for realtime streams, where data
 may be dropped if not read in time. Use this option to enable infinite buffers
 for all inputs, use @option{-noinfbuf} to disable it.
 
+@item -filter_threads @var{nb_threads}
+Defines how many threads are used to process a filter pipeline. Each pipeline
+will produce a thread pool with this many threads available for parallel
+processing. The default is 0 which means that the thread count will be
+determined by the number of available CPUs.
+
 @end table
 
 @section While playing

fftools/ffplay.c

@@ -353,6 +353,7 @@ static char *afilters = NULL;
 #endif
 static int autorotate = 1;
 static int find_stream_info = 1;
+static int filter_nbthreads = 0;
 
 /* current context */
 static int is_full_screen;
@@ -1954,6 +1955,7 @@ static int configure_audio_filters(VideoState *is, const char *afilters, int for
     avfilter_graph_free(&is->agraph);
     if (!(is->agraph = avfilter_graph_alloc()))
         return AVERROR(ENOMEM);
+    is->agraph->nb_threads = filter_nbthreads;
 
     while ((e = av_dict_get(swr_opts, "", e, AV_DICT_IGNORE_SUFFIX)))
         av_strlcatf(aresample_swr_opts, sizeof(aresample_swr_opts), "%s=%s:", e->key, e->value);
@@ -2162,6 +2164,7 @@ static int video_thread(void *arg)
                 ret = AVERROR(ENOMEM);
                 goto the_end;
             }
+            graph->nb_threads = filter_nbthreads;
             if ((ret = configure_video_filters(graph, is, vfilters_list ? vfilters_list[is->vfilter_idx] : NULL, frame)) < 0) {
                 SDL_Event event;
                 event.type = FF_QUIT_EVENT;
@@ -3611,6 +3614,7 @@ static const OptionDef options[] = {
     { "autorotate", OPT_BOOL, { &autorotate }, "automatically rotate video", "" },
     { "find_stream_info", OPT_BOOL | OPT_INPUT | OPT_EXPERT, { &find_stream_info },
         "read and decode the streams to fill missing information with heuristics" },
+    { "filter_threads", HAS_ARG | OPT_INT | OPT_EXPERT, { &filter_nbthreads }, "number of filter threads per graph" },
     { NULL, },
 };