fftools/cmdutils.c: Add cmd line option to override detection of cpu count.

doc/fftools-common-opts.texi

@@ -353,6 +353,13 @@ Possible flags for this option are:
 @end table
 @end table
 
+@item -cpucount @var{count} (@emph{global})
+Override detection of CPU count. This option is intended
+for testing. Do not use it unless you know what you're doing.
+@example
+ffmpeg -cpucount 2
+@end example
+
 @item -max_alloc @var{bytes}
 Set the maximum size limit for allocating a block on the heap by ffmpeg's
 family of malloc functions. Exercise @strong{extreme caution} when using

fftools/cmdutils.c

@@ -71,6 +71,7 @@ AVDictionary *format_opts, *codec_opts, *resample_opts;
 static FILE *report_file;
 static int report_file_level = AV_LOG_DEBUG;
 int hide_banner = 0;
+int cpu_count = -1;
 
 enum show_muxdemuxers {
     SHOW_DEFAULT,
@@ -853,6 +854,32 @@ int opt_cpuflags(void *optctx, const char *opt, const char *arg)
     return 0;
 }
 
+int opt_cpucount(void *optctx, const char *opt, const char *arg)
+{
+    int ret;
+    int count;
+
+    static const AVOption opts[] = {
+        {"count", NULL, 0, AV_OPT_TYPE_INT, { .i64 = -1}, -1, INT_MAX, NULL},
+        {NULL},
+    };
+    static const AVClass class = {
+        .class_name = "cpucount",
+        .item_name  = av_default_item_name,
+        .option     = opts,
+        .version    = LIBAVUTIL_VERSION_INT,
+    };
+    const AVClass *pclass = &class;
+
+    ret = av_opt_eval_int(&pclass, opts, arg, &count);
+
+    if (!ret) {
+        av_force_cpu_count(count);
+    }
+
+    return ret;
+}
+
 int opt_loglevel(void *optctx, const char *opt, const char *arg)
 {
     const struct { const char *name; int level; } log_levels[] = {

fftools/cmdutils.h

@@ -50,6 +50,7 @@ extern AVDictionary *sws_dict;
 extern AVDictionary *swr_opts;
 extern AVDictionary *format_opts, *codec_opts, *resample_opts;
 extern int hide_banner;
+extern int cpu_count;
 
 /**
  * Register a program-specific cleanup routine.
@@ -88,6 +89,11 @@ void log_callback_help(void* ptr, int level, const char* fmt, va_list vl);
  */
 int opt_cpuflags(void *optctx, const char *opt, const char *arg);
 
+/**
+ * Override the cpucount.
+ */
+int opt_cpucount(void *optctx, const char *opt, const char *arg);
+
 /**
  * Fallback for options that are not explicitly handled, these will be
  * parsed through AVOptions.
@@ -239,6 +245,7 @@ void show_help_options(const OptionDef *options, const char *msg, int req_flags,
     { "report",      0,                    { .func_arg = opt_report },       "generate a report" },                     \
     { "max_alloc",   HAS_ARG,              { .func_arg = opt_max_alloc },    "set maximum size of a single allocated block", "bytes" }, \
     { "cpuflags",    HAS_ARG | OPT_EXPERT, { .func_arg = opt_cpuflags },     "force specific cpu flags", "flags" },     \
+    { "cpucount",    HAS_ARG | OPT_EXPERT, { .func_arg = opt_cpucount },     "force specific cpu count", "count" },     \
     { "hide_banner", OPT_BOOL | OPT_EXPERT, {&hide_banner},     "do not show program banner", "hide_banner" },          \
     CMDUTILS_COMMON_OPTIONS_AVDEVICE                                                                                    \