diff -Naur b/ffserver.c a/ffserver.c
--- b/ffserver.c	2011-11-04 22:46:58.000000000 +0100
+++ a/ffserver.c	2011-11-07 01:48:14.158188058 +0100
@@ -2161,6 +2161,7 @@
         http_log("could not open %s: %d\n", input_filename, ret);
         return -1;
     }
+    if (buf_size > 0) ffio_set_buf_size(s->pb, buf_size);
     s->flags |= AVFMT_FLAG_GENPTS;
     c->fmt_in = s;
     if (strcmp(s->iformat->name, "ffm") && av_find_stream_info(c->fmt_in) < 0) {
@@ -3680,6 +3681,8 @@
             int matches = 0;
 
             if (avformat_open_input(&s, feed->feed_filename, NULL, NULL) >= 0) {
+                /* set buffer size */
+                ffio_set_buf_size(s->pb, FFM_PACKET_SIZE);
                 /* Now see if it matches */
                 if (s->nb_streams == feed->nb_streams) {
                     matches = 1;