Index: mpcommon.h
===================================================================
--- mpcommon.h	（版本 23698）
+++ mpcommon.h	（工作副本）
@@ -5,3 +5,4 @@
 extern sub_data *subdata;
 extern subtitle *vo_sub_last;
 void update_subtitles(sh_video_t *sh_video, demux_stream_t *d_dvdsub, int reset);
+unsigned get_num_processors(void);
Index: mpcommon.c
===================================================================
--- mpcommon.c	（版本 23698）
+++ mpcommon.c	（工作副本）
@@ -1,4 +1,18 @@
 #include <stdlib.h>
+
+#if defined(WIN32)
+#include <windows.h>
+#elif defined(SYS_LINUX)
+#include <sched.h>
+#elif defined(SYS_BEOS)
+#include <kernel/OS.h>
+#elif defined(SYS_MACOSX)
+#include <sys/types.h>
+#include <sys/sysctl.h>
+#elif defined(sun)
+#include <unistd.h>
+#endif
+
 #include "stream/stream.h"
 #include "libmpdemux/demuxer.h"
 #include "libmpdemux/stheader.h"
@@ -138,3 +152,37 @@
     }
     current_module=NULL;
 }
+
+static unsigned popcnt(unsigned n)
+{
+    unsigned ret, i;
+    for (ret = 0, i = 0; i < sizeof(n) * 8; i++)
+	ret += (n >> i) & 1;
+    return ret;
+}
+
+unsigned get_num_processors(void)
+{
+    unsigned ret = 1;
+#if defined(WIN32)
+    DWORD proc, sys;
+    if (GetProcessAffinityMask(GetCurrentProcess(), &proc, &sys))
+	ret = popcnt(proc);
+#elif defined(SYS_LINUX)
+    cpu_set_t aff;
+    if (sched_getaffinity(0, sizeof(aff), &aff) != -1)
+	ret = popcnt(aff);
+#elif defined(SYS_BEOS)
+    system_info info;
+    get_system_info(&info);
+    ret = info.cpu_count;
+#elif defined(SYS_MACOSX)
+    size_t len = sizeof(ret);
+    if (sysctlbyname("hw.ncpu", &ret, &len, NULL, 0))
+	ret = 1;
+#elif defined(sun)
+    ret = sysconf(_SC_NPROCESSORS_CONF);
+#endif
+    return ret;
+}
+
Index: libmpcodecs/vd_ffmpeg.c
===================================================================
--- libmpcodecs/vd_ffmpeg.c	（版本 23698）
+++ libmpcodecs/vd_ffmpeg.c	（工作副本）
@@ -88,7 +89,7 @@
 static char *lavc_param_skip_loop_filter_str = NULL;
 static char *lavc_param_skip_idct_str = NULL;
 static char *lavc_param_skip_frame_str = NULL;
-static int lavc_param_threads=1;
+static int lavc_param_threads=0;
 static int lavc_param_bitexact=0;
 
 m_option_t lavc_decode_opts_conf[]={
@@ -109,7 +110,7 @@
 	{"skiploopfilter", &lavc_param_skip_loop_filter_str, CONF_TYPE_STRING, 0, 0, 0, NULL},
 	{"skipidct", &lavc_param_skip_idct_str, CONF_TYPE_STRING, 0, 0, 0, NULL},
 	{"skipframe", &lavc_param_skip_frame_str, CONF_TYPE_STRING, 0, 0, 0, NULL},
-        {"threads", &lavc_param_threads, CONF_TYPE_INT, CONF_RANGE, 1, 8, NULL},
+        {"threads", &lavc_param_threads, CONF_TYPE_INT, CONF_RANGE, 0, 8, NULL},
         {"bitexact", &lavc_param_bitexact, CONF_TYPE_FLAG, 0, 0, CODEC_FLAG_BITEXACT, NULL},
 	{NULL, NULL, 0, 0, 0, 0, NULL}
 };
@@ -402,6 +403,8 @@
     if(sh->bih)
 	avctx->bits_per_sample= sh->bih->biBitCount;
 
+    if(lavc_param_threads == 0)
+        lavc_param_threads = get_num_processors();
     if(lavc_param_threads > 1)
         avcodec_thread_init(avctx, lavc_param_threads);
     /* open it */
Index: libmpcodecs/ve_lavc.c
===================================================================
--- libmpcodecs/ve_lavc.c	（版本 23698）
+++ libmpcodecs/ve_lavc.c	（工作副本）
@@ -141,7 +141,7 @@
 static int lavc_param_nssew= 8;
 static int lavc_param_closed_gop = 0;
 static int lavc_param_dc_precision = 8;
-static int lavc_param_threads= 1;
+static int lavc_param_threads= 0;
 static int lavc_param_turbo = 0;
 static int lavc_param_brd_scale = 0;
 static int lavc_param_bidir_refine = 0;
@@ -285,7 +285,7 @@
 	{"top", &lavc_param_top, CONF_TYPE_INT, CONF_RANGE, -1, 1, NULL},
         {"qns", &lavc_param_qns, CONF_TYPE_INT, CONF_RANGE, 0, 1000000, NULL},
         {"nssew", &lavc_param_nssew, CONF_TYPE_INT, CONF_RANGE, 0, 1000000, NULL},
-	{"threads", &lavc_param_threads, CONF_TYPE_INT, CONF_RANGE, 1, 8, NULL},
+	{"threads", &lavc_param_threads, CONF_TYPE_INT, CONF_RANGE, 0, 8, NULL},
 	{"turbo", &lavc_param_turbo, CONF_TYPE_FLAG, 0, 0, 1, NULL},
 	{"brd_scale", &lavc_param_brd_scale, CONF_TYPE_INT, CONF_RANGE, 0, 10, NULL},
 	{"bidir_refine", &lavc_param_bidir_refine, CONF_TYPE_INT, CONF_RANGE, 0, 4, NULL},
@@ -663,6 +663,8 @@
 	vf->priv->pic->quality = (int)(FF_QP2LAMBDA * lavc_param_vqscale + 0.5);
     }
 
+    if(lavc_param_threads == 0)
+        lavc_param_threads = get_num_processors();
     if(lavc_param_threads > 1)
 	avcodec_thread_init(lavc_venc_context, lavc_param_threads);
 
Index: DOCS/man/en/mplayer.1
===================================================================
--- DOCS/man/en/mplayer.1	（版本 23698）
+++ DOCS/man/en/mplayer.1	（工作副本）
@@ -4246,8 +4246,8 @@
 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 only)"
-number of threads to use for decoding (default: 1)
+.IPs "threads=<0\-8> (MPEG-1/2 only)"
+number of threads to use for decoding, 0 for autodetect (default)
 .IPs vismv=<value>
 Visualize motion vectors.
 .RSss
@@ -7242,8 +7242,8 @@
 Do not use this option unless you know exactly what you are doing.
 .
 .TP
-.B threads=<1\-8>
-Maximum number of threads to use (default: 1).
+.B threads=<0\-8>
+Maximum number of threads to use, 0 for autodetect (default).
 May have a slight negative effect on motion estimation.
 .RE
 .