vd_ffmpeg: set thread count to number of cores on machine by default

Make "-lavdopts threads=0" mean an autodetected number of threads, and
make that the default value of the option. Also increase the upper
limit of the option from 8 to 16. Add new file osdep/numcores.c which
tries to determine the number of cores available on the machine.

numcores.c is based (heavily modified) on public domain numcpus.c by
Philip Willoughby <pgw99@doc.ic.ac.uk>, downloaded from
http://csgsoft.doc.ic.ac.uk/numcpus/

DOCS/man/en/mplayer.1

@@ -4909,8 +4909,12 @@ This degrades quality a lot of in almost all cases
 Skips decoding of frames completely.
 Big speedup, but jerky motion and sometimes bad artifacts
 (see skiploopfilter for available skip values).
-.IPs "threads=<1\-8> (MPEG-1/2 and H.264 only)"
-number of threads to use for decoding (default: 1)
+.IPs "threads=<0\-16>"
+Number of threads to use for decoding.
+Whether threading is actually supported depends on codec.
+0 means autodetect number of cores on the machine and use that, up to the
+maximum of 16.
+(default: 0)
 .IPs vismv=<value>
 Visualize motion vectors.
 .RSss

Makefile

@@ -505,6 +505,7 @@ SRCS_COMMON = asxparser.c \
               libvo/osd.c \
               libvo/sub.c \
               osdep/findfiles.c \
+              osdep/numcores.c \
               osdep/$(GETCH) \
               osdep/$(TIMER) \
               stream/open.c \

defaultopts.c

@@ -50,7 +50,6 @@ void set_default_mplayer_options(struct MPOpts *opts)
             .workaround_bugs = 1, // autodetect
             .error_resilience = 2,
             .error_concealment = 3,
-            .threads = 1,
         },
         .input = {
              .config_file = "input.conf",

libmpcodecs/vd_ffmpeg.c

@@ -37,6 +37,7 @@
 #include "img_format.h"
 #include "libmpdemux/stheader.h"
 #include "codec-cfg.h"
+#include "osdep/numcores.h"
 #include "vd_ffmpeg.h"
 
 static const vd_info_t info = {
@@ -105,7 +106,7 @@ const m_option_t lavc_decode_opts_conf[]={
     OPT_STRING("skiploopfilter", lavc_param.skip_loop_filter_str, 0),
     OPT_STRING("skipidct", lavc_param.skip_idct_str, 0),
     OPT_STRING("skipframe", lavc_param.skip_frame_str, 0),
-    OPT_INTRANGE("threads", lavc_param.threads, 0, 1, 8),
+    OPT_INTRANGE("threads", lavc_param.threads, 0, 0, 16),
     OPT_FLAG_CONSTANTS("bitexact", lavc_param.bitexact, 0, 0, CODEC_FLAG_BITEXACT),
     OPT_STRING("o", lavc_param.avopt, 0),
     {NULL, NULL, 0, 0, 0, 0, NULL}
@@ -222,11 +223,23 @@ static int init(sh_video_t *sh){
         avctx->slice_flags = SLICE_FLAG_CODED_ORDER|SLICE_FLAG_ALLOW_FIELD;
     }
 
+    if (lavc_param->threads == 0) {
+        int threads = default_thread_count();
+        if (threads < 1) {
+            mp_msg(MSGT_DECVIDEO, MSGL_WARN, "[VD_FFMPEG] Could not determine "
+                   "thread count to use, defaulting to 1.\n");
+            threads = 1;
+        }
+        threads = FFMIN(threads, 16);
+        lavc_param->threads = threads;
+    }
     /* Our get_buffer and draw_horiz_band callbacks are not safe to call
      * from other threads. */
     if (lavc_param->threads > 1) {
         ctx->do_dr1 = false;
         ctx->do_slices = false;
+        mp_tmsg(MSGT_DECVIDEO, MSGL_INFO, "Asking decoder to use "
+                "%d threads if supported.\n", lavc_param->threads);
     }
 
     if(ctx->do_dr1){

osdep/numcores.c

@@ -0,0 +1,66 @@
+/*
+ * This file is part of MPlayer.
+ *
+ * MPlayer is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * MPlayer is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with MPlayer; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+
+#include "numcores.h"
+
+#ifdef _SC_NPROCESSORS_ONLN
+#define SCNAME _SC_NPROCESSORS_ONLN
+#elif defined _SC_NPROC_ONLN
+#define SCNAME _SC_NPROC_ONLN
+#elif defined _SC_CRAY_NCPU
+#define SCNAME _SC_CRAY_NCPU
+#endif
+
+#ifdef _WIN32
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+int default_thread_count(void)
+{
+    SYSTEM_INFO info;
+    GetSystemInfo(&info);
+    int count = info.dwNumberOfProcessors;
+    if (count > 0)
+        return count;
+    return -1;
+}
+
+#elif defined SCNAME
+
+int default_thread_count(void)
+{
+    long nprocs = sysconf(SCNAME);
+    if (nprocs < 1)
+        return -1;
+    return nprocs;
+}
+
+#else
+
+int default_thread_count(void)
+{
+    return -2;
+}
+
+#endif

osdep/numcores.h

@@ -0,0 +1 @@
+int default_thread_count(void);