ffmpeg: parameters for filter thread counts

Enables specifying how many threads are available to each filtergraph.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

doc/ffmpeg.texi

@@ -415,6 +415,11 @@ This option is similar to @option{-filter}, the only difference is that its
 argument is the name of the file from which a filtergraph description is to be
 read.
 
+@item -filter_threads @var{nb_threads} (@emph{global})
+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 the number of available CPUs.
+
 @item -pre[:@var{stream_specifier}] @var{preset_name} (@emph{output,per-stream})
 Specify the preset for matching stream(s).
 
@@ -1201,6 +1206,11 @@ To generate 5 seconds of pure red video using lavfi @code{color} source:
 ffmpeg -filter_complex 'color=c=red' -t 5 out.mkv
 @end example
 
+@item -filter_complex_threads @var{nb_threads} (@emph{global})
+Defines how many threads are used to process a filter_complex graph.
+Similar to filter_threads but used for @code{-filter_complex} graphs only.
+The default is the number of available CPUs.
+
 @item -lavfi @var{filtergraph} (@emph{global})
 Define a complex filtergraph, i.e. one with arbitrary number of inputs and/or
 outputs. Equivalent to @option{-filter_complex}.

ffmpeg.h

@@ -581,6 +581,9 @@ extern AVIOContext *progress_avio;
 extern float max_error_rate;
 extern char *videotoolbox_pixfmt;
 
+extern int filter_nbthreads;
+extern int filter_complex_nbthreads;
+
 extern const AVIOInterruptCB int_cb;
 
 extern const OptionDef options[];

ffmpeg_filter.c

@@ -39,6 +39,9 @@
 #include "libavutil/imgutils.h"
 #include "libavutil/samplefmt.h"
 
+int filter_nbthreads = -1;
+int filter_complex_nbthreads = -1;
+
 static const enum AVPixelFormat *get_compliance_unofficial_pix_fmts(enum AVCodecID codec_id, const enum AVPixelFormat default_formats[])
 {
     static const enum AVPixelFormat mjpeg_formats[] =
@@ -991,6 +994,8 @@ int configure_filtergraph(FilterGraph *fg)
         char args[512];
         AVDictionaryEntry *e = NULL;
 
+        fg->graph->nb_threads = filter_complex_nbthreads;
+
         args[0] = 0;
         while ((e = av_dict_get(ost->sws_dict, "", e,
                                 AV_DICT_IGNORE_SUFFIX))) {
@@ -1021,6 +1026,8 @@ int configure_filtergraph(FilterGraph *fg)
         e = av_dict_get(ost->encoder_opts, "threads", NULL, 0);
         if (e)
             av_opt_set(fg->graph, "threads", e->value, 0);
+    } else {
+        fg->graph->nb_threads = filter_nbthreads;
     }
 
     if ((ret = avfilter_graph_parse2(fg->graph, graph_desc, &inputs, &outputs)) < 0)

ffmpeg_opt.c

@@ -3381,12 +3381,16 @@ 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 },
+        "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" },
     { "reinit_filter",  HAS_ARG | OPT_INT | OPT_SPEC | OPT_INPUT,    { .off = OFFSET(reinit_filters) },
         "reinit filtergraph on input parameter changes", "" },
     { "filter_complex", HAS_ARG | OPT_EXPERT,                        { .func_arg = opt_filter_complex },
         "create a complex filtergraph", "graph_description" },
+    { "filter_complex_threads", HAS_ARG | OPT_INT,                   { &filter_complex_nbthreads },
+        "number of threads for -filter_complex" },
     { "lavfi",          HAS_ARG | OPT_EXPERT,                        { .func_arg = opt_filter_complex },
         "create a complex filtergraph", "graph_description" },
     { "filter_complex_script", HAS_ARG | OPT_EXPERT,                 { .func_arg = opt_filter_complex_script },