threads: default to automatic thread count detection

Changelog

@@ -6,6 +6,7 @@ version <next>:
 
 - Indeo 4 decoder
 - SMJPEG demuxer
+- Automatic thread count based on detection number of (available) CPU cores
 
 
 version 0.8_beta1:

libavcodec/options.c

@@ -370,7 +370,7 @@ static const AVOption options[]={
 {"float", NULL, 0, AV_OPT_TYPE_CONST, {.dbl = FF_AA_FLOAT }, INT_MIN, INT_MAX, V|D, "aa"},
 #endif
 {"qns", "quantizer noise shaping", OFFSET(quantizer_noise_shaping), AV_OPT_TYPE_INT, {.dbl = DEFAULT }, INT_MIN, INT_MAX, V|E},
-{"threads", NULL, OFFSET(thread_count), AV_OPT_TYPE_INT, {.dbl = 1 }, 0, INT_MAX, V|E|D, "threads"},
+{"threads", NULL, OFFSET(thread_count), AV_OPT_TYPE_INT, {.dbl = 0 }, 0, INT_MAX, V|E|D, "threads"},
 {"auto", "detect a good number of threads", 0, AV_OPT_TYPE_CONST, {.dbl = 0 }, INT_MIN, INT_MAX, V|E|D, "threads"},
 {"me_threshold", "motion estimaton threshold", OFFSET(me_threshold), AV_OPT_TYPE_INT, {.dbl = DEFAULT }, INT_MIN, INT_MAX, V|E},
 {"mb_threshold", "macroblock threshold", OFFSET(mb_threshold), AV_OPT_TYPE_INT, {.dbl = DEFAULT }, INT_MIN, INT_MAX, V|E},

libavcodec/version.h

@@ -22,7 +22,7 @@
 
 #define LIBAVCODEC_VERSION_MAJOR 53
 #define LIBAVCODEC_VERSION_MINOR 32
-#define LIBAVCODEC_VERSION_MICRO  0
+#define LIBAVCODEC_VERSION_MICRO  1
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \

libavformat/utils.c

@@ -2268,9 +2268,14 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
     int i, count, ret, read_size, j;
     AVStream *st;
     AVPacket pkt1, *pkt;
+    AVDictionary *one_thread_opt = NULL;
     int64_t old_offset = avio_tell(ic->pb);
     int orig_nb_streams = ic->nb_streams;        // new streams might appear, no options for those
 
+    /* this function doesn't flush the decoders, so force thread count
+     * to 1 to fix behavior when thread count > number of frames in the file */
+    av_dict_set(&one_thread_opt, "threads", "1", 0);
+
     for(i=0;i<ic->nb_streams;i++) {
         AVCodec *codec;
         st = ic->streams[i];
@@ -2300,12 +2305,13 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
         /* Ensure that subtitle_header is properly set. */
         if (st->codec->codec_type == AVMEDIA_TYPE_SUBTITLE
             && codec && !st->codec->codec)
-            avcodec_open2(st->codec, codec, options ? &options[i] : NULL);
+            avcodec_open2(st->codec, codec, options ? &options[i] : &one_thread_opt);
 
         //try to just open decoders, in case this is enough to get parameters
         if(!has_codec_parameters(st->codec)){
             if (codec && !st->codec->codec)
-                avcodec_open2(st->codec, codec, options ? &options[i] : NULL);
+                avcodec_open2(st->codec, codec, options ? &options[i]
+                              : &one_thread_opt);
         }
     }
 
@@ -2444,7 +2450,8 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
            least one frame of codec data, this makes sure the codec initializes
            the channel configuration and does not only trust the values from the container.
         */
-        try_decode_frame(st, pkt, (options && i < orig_nb_streams )? &options[i] : NULL);
+        try_decode_frame(st, pkt, (options && i < orig_nb_streams )? &options[i]
+                         : &one_thread_opt);
 
         st->codec_info_nb_frames++;
         count++;
@@ -2549,8 +2556,12 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
 #endif
 
  find_stream_info_err:
-    for (i=0; i < ic->nb_streams; i++)
+    for (i=0; i < ic->nb_streams; i++) {
+        if (ic->streams[i]->codec)
+            ic->streams[i]->codec->thread_count = 0;
         av_freep(&ic->streams[i]->info);
+    }
+    av_dict_free(&one_thread_opt);
     return ret;
 }