Welcome to Cyber Radio 1 !


Cyber Radio 1 is the distribution name of the live Internet audio
broadcast system that I wrote for the Georiga Tech student radio
station, WREK Atlanta 91.1 FM. WREK has been using this system for the
past year under the name WREK-NET.


Cyber Radio 1 is a client/server system. The server continually reads
digital data from the audio device (e.g. /dev/audio) and multiplexes it
out to any number of connected clients. Connected clients in turn,
receive the digital audio data to play out of their audio device.


The Cyber Radio 1 system has been tested to work with any Sun Sparc,
Linux, or BSD system with an audio device. The client program will work
on any SGI workstation as well.  It's reported that it should work on
HP/UX workstations as well. It could potentially work on NeXT machines
and other systems with minimal hacking. There is no reason why a
Windows version couldn't be made.



Cyber Radio 1 consists of the following programs:

     A server program. 

     A client program. 

     A server utility program that displays current client/server
     connection information. 

     Other utility programs to manage connections, including a sample
     program that can send text messages to clients. 

     A special version of the client program and shell script that sends
     short samples of audio data over the WWW as a CGI-BIN program. 


Cyber Radio 1 is being distributed under the GNU General Public
License. The GNU GPL is gives everyone the right to have access to the
source code, the right to modify, and redistribute under the terms of
the GNU GPL.  Read the file labeled COPYING for more information.


Cyber Radio 1 is intended for radio stations with a fast connection to
the Internet to broadcast their sound on. It is especially hoped that
other computer hackers that work in college radio will attempt to use
it and perhaps improve it.


Although it is not as sophisticated as Cu-See-Me, RealAudio, or other
net audio software, the sound quality of CR1 is better suited for
music. In addition, the client and server processes use minimal CPU and
network resources.


Cyber Radio 1 has been written in C and will compile on any UNIX
system. After downloading the package, read the file labeled "INSTALL"
for instructions on how to build it into a network audio broadcast system.



Below is a list of all the files included


audio_sgi.c   - SGI AUDIO CODE
audio_sgi.h   - SGI AUDIO CODE
tables.c      - SGI AUDIO CODE
tables.h      - SGI AUDIO CODE

cr1.c         - CLIENT PROGRAM 
cr1.h         - CLIENT PROGRAM

request.c     - SERVER PROGRAM
server.c      - SERVER PROGRAM
bconsole.c    - SERVER BROADCAST CONSOLE

shm.c         - IPC SERVICES FOR ALL SERVER PROGRAMS
shm.h         - IPC SERVICES FOR ALL SERVER PROGRAMS

talk.c        - SERVER UTILITY PROGRAM
terminate.c   - SERVER UTILITY PROGRAM

README        - THIS FILE
COPYING       - GNU PUBLIC LICENSE
INSTALL       - INSTALLATION GUIDE


webdemo.c     - WWW demo program of CR1  (Solaris)
webdemo.cgi   - WWW demo cgi script
cr1.py        - Python version of the client program

MISC          - information about the python and web demo files

packet.format - The UDP packet format for CR1 client server communication
protocol      - The CR1 protocol

HACKING       - Information for people interested in improving CR1


Users of this software package are expected to have read the file
COPYING.  This is the GNU public license.  It specifies the terms
of the software's distribution and it's warranty.


Special thanks to the following people:

eric.buckhalt@wrek.radio
strick@techwood
heather@utexas
captain@actlab
kral@bsdi.hefnet.org
aaron@rama.hefnet.org
joel@skeeter.hefnet.org
joe.dennison@ec85.residence
iansmith@stein.club
keith@multimedia
will.moore@wrek.radio
gregh@punk.rock
rick@pink.palace
all@oit.gatech.edu

stevie.lefcort@wrek.radio
chris.campbell@duck.wrek.radio
richard.musterer@wrek.radio
richard.westrick@wrek.radio
linda.deerborne@wrek.radio
jason.pickering@french.toast

bhollon@mellon
skibo@sgi


Thank you again to Ian Smith for the SGI Audio code.

-------------------------
New! Improved!

If you have a net connection like mine, you will have discovered that 
the cr1 client, in it's original state, doesn't work very well if you
are more than a few network hops away from the broadcaster.  The UDP
packets on which this client get dropped, show up late, etc.  To improve
sound delivery, I have added a circular buffer (fifo) to buffer up
packets as they arrive.  This means it will take a few seconds for the
client to start up, but when it does, the sound will be more continuous.

The buffer helps with reception, but it is not perfect.  UDP packets are
sent in real time, and if one is lost, there *will* be a pause or skip
in the music.  To this end, I have begun to experiment with dynamic rate
adaptation, to ever-so-slightly slow things down so that the audio
pauses due missing packets and gaps don't result in silence.  However,
the rate adaptation code is incomplete, and is currently disabled.  I
was unable to complete this work because thre seems to be bugs in the
version of ossfree I am running (v3.8beta5) and/or in linux v.2.1.26.
Basically, I never get EAGAIN on a full audio device, and if I overstuff
the device, it goes into an infinite loop. Sigh.  

Another idea I would like to discuss with anyone is a semi-gaurenteed 
packet delivery scheme for UDP, more suitable for real-time streams such
as audio and video.  The idea is that packets are given sequence
numbers, and that packets that aren't delivered get re-requested. Of
course, extremely stale re-requests are ignored, as is appropriate for
real-time streams.

The semi-gaurenteed UDP has several immense advatages as compared to
TCP. First, the audio server does not need to keep O(n) connections to n
clients: it only needs to keep the last ten or twenty seconds worth of
data (i.e. only 100K to 200K of data for 8K ulaw sound).  If
re-transimit requests show up for packets older than that, they are
ignored.  Also, unlike tcpip, there is no acknowledgement of receipt
send.  Instead, there is an acknowledgement of loss.  Anyone interested
in playing with this, please write me.

15 Feb 1997 -- Linas Vepstas linas@fc.net