Tip from http://lists.apple.com/archives/streaming-server-users/2003/Oct/msg00125.html

Advice on trying to reduce latency on the streaming server.

The general view was to reduce the
<PREF NAME="reflector_buffer_size_sec" TYPE="UInt32" >0</PREF> config to 0.

Some people said this worked well, others didn't have an luck.

I had problems, but have figured it out so would like to share my findings.

If you open the config file in something like BBEdit (something that
reports on when a file changes on disk) you can see what is going on a
bit easier When I changed my config file I tried restarting QTSS (both
through the web interface and from the command line doing various kill
-HUP and straight kill). However when I tabbed back to BBEdit, it
reported that the config file had changed, and sure enough, when i
reloaded, the previous delay settings were still there. This made me
think that there must be a process that is writing the config file
back at regular intervals. Why? I don't know....

To get your changes to work every time do this.

open terminal
ps -auwx | grep -i stream
root 376 0.0 0.0 14684 112 ?? Ss 1Jan70 0:00.00 /usr/sbin/QuickTimeStreamingServer
root 377 0.0 0.2 16616 880 ?? S 1Jan70 0:00.49 /usr/sbin/QuickTimeStreamingServer
root 379 0.0 0.1 3764 480 ?? Ss 1Jan70 0:00.02 perl /usr/sbin/streamingadminserver.pl
robin 456 0.0 0.0 1116 4 std R+ 12:16PM 0:00.00 grep -i stream

kill ALL streaming related processes

now change your config file.
restart QTSS through the web interface

I have got the latency down to under a second over a wireless lan with
moderate MPEG4 encoding settings.