Enable AVFMT_FLAG_NONBLOCK.

Originally committed as revision 17785 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -2805,6 +2805,7 @@ static void opt_input_file(const char *filename)
     ic->video_codec_id   = find_codec_or_die(video_codec_name   , CODEC_TYPE_VIDEO   , 0);
     ic->audio_codec_id   = find_codec_or_die(audio_codec_name   , CODEC_TYPE_AUDIO   , 0);
     ic->subtitle_codec_id= find_codec_or_die(subtitle_codec_name, CODEC_TYPE_SUBTITLE, 0);
+    ic->flags |= AVFMT_FLAG_NONBLOCK;
 
     /* open the input file with generic libav function */
     err = av_open_input_file(&ic, filename, file_iformat, 0, ap);
@@ -3395,6 +3396,7 @@ static void opt_output_file(const char *filename)
     oc->preload= (int)(mux_preload*AV_TIME_BASE);
     oc->max_delay= (int)(mux_max_delay*AV_TIME_BASE);
     oc->loop_output = loop_output;
+    oc->flags |= AVFMT_FLAG_NONBLOCK;
 
     set_context_opts(oc, avformat_opts, AV_OPT_FLAG_ENCODING_PARAM);