--- stream/asf_mmst_streaming.c	2009-03-20 09:06:31.000000000 +0100
+++ stream/asf_mmst_streaming.c.ultimo_riferimento3	2009-03-20 09:04:44.000000000 +0100
@@ -84,6 +84,7 @@
    ASFtype stream_type[MAX_STREAMS];
    uint32_t stream_bitrates[MAX_STREAMS];
    uint32_t packet_size;
+   uint64_t preroll;
    int audio_id, video_id;
 };
 
@@ -324,6 +325,16 @@
   }
 }
 
+static void adjust_prebuffer_size(streaming_ctrl_t *streaming_ctrl)
+{
+    struct asf_mms_streaming_ctrl *mms_ctrl = streaming_ctrl->data;
+    uint32_t max_bitrate = mms_ctrl->stream_bitrates[mms_ctrl->audio_id];
+    max_bitrate += mms_ctrl->stream_bitrates[mms_ctrl->video_id];
+
+    if (max_bitrate)
+        streaming_ctrl->prebuffer_size = (unsigned int)((mms_ctrl->preroll / 1000.0) * (max_bitrate / 8.0));
+}
+
 static int interp_header (uint8_t *header, int len, streaming_ctrl_t *streaming_ctrl)
 {
     struct asf_mms_streaming_ctrl *mms_ctrl = streaming_ctrl->data;
@@ -335,6 +346,8 @@
         pos += sizeof(ASF_file_header_t);
         if (pos > len) goto len_err_out;
         mms_ctrl->packet_size = (uint32_t) AV_RL32(&file_properties->max_packet_size);
+        mms_ctrl->preroll = file_properties->preroll;
+        streaming_ctrl->prebuffer_size = (unsigned int)((file_properties->preroll / 1000.0) * (file_properties->max_bitrate / 8.0));
     }
     else {
         mp_msg(MSGT_NETWORK, MSGL_FATAL, "File properties object in ASF header not found, exiting.\n");
@@ -667,6 +680,8 @@
       }
   }
 
+  adjust_prebuffer_size(stream->streaming_ctrl);
+
   for (i = 1; i < MAX_STREAMS; i++) {
       if (mms_ctrl->stream_type[i] != ASF_NO_STREAM) {
           num_stream_ids++;