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Volker Fischer 2008-07-17 19:07:12 +00:00
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README
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@ -1,5 +1,5 @@
/******************************************************************************\
* Copyright (c) 2004-2006
* Copyright (c) 2004-2008
*
* Author(s):
* Volker Fischer
@ -25,23 +25,30 @@
llcon
-----
Low-Latency Connection / client and server
Low-Latency Connection / client and server (http://llcon.sourceforge.net)
OBJECTIVES:
The task is to build a client/server software to enable musicians to play together
over the internet. Target internet connection is DSL with 256 kbps upstream and
1 Mbit downstream. The server software must be located at a server with a very
fast internet connection (at least 1 Mbps for up- and downstream).
INTRODUCTION:
The llcon software enables musicians to play together over the internet. The
way it works is that there must be one server which collects the audio data
from each client, mixes all together and sends the mix back to each client.
The minimum internet connection speed at each client must be 256 kbps upstream
and 1 Mbit downstream. The server software must be located at a server with a
very fast internet connection (at least 1 Mbps for up- and downstream) and a
very low ping time. To get satisfactory results, the ping time from the client
computer to the server should not exceed 30 ms average and the network jitter
should be as low as 2-5 ms (To get a low ping time on DSL connections, an
extra option "DSL fast path" should be enabled by your internet provider).
To get sufficient results, a sample rate of 24 kHz (mono channel) was chosen. An
audio compression algorithm with very low delay is IMA-ADPCM (delay is just one
sample). This gives a raw compressed audio data rate of 96 kbps.
Technical details
To get sufficient results, a sample rate of 24 kHz (mono channel) was chosen.
The audio compression algorithm IMA-ADPCM with very low delay is used which
results in a raw compressed audio data rate of 96 kbps. First tests showed
that an upstream of 128 kbps is too slow for using the llcon software. At
least 256 kbps upstream bandwidth is required.
Target hardware setup at the client is stereo audio input signal with one channel
is the instrument and the other channel is a microphone signal. On the microphne
channel a reverberation effect can be applied (maybe at a later time other audio
effects are added).
The llcon software package includes both, the server and the client
functionality which can be selected by using command line arguments.
MANUAL:
@ -51,14 +58,13 @@ Start the llcon server on a remote computer with fast internet access. Start the
llcon client on your local computer and connect your sound card with your
instrument/microphone and headphone and type in the IP address of the server.
There are levelers for adjusting the sound card (in/out) and network buffer sizes.
It seems that 2 blocks for network buffer is optimal choice. For the sound card
It seems that 2 blocks for network buffer is an optimal choice. For the sound card
buffer, try to make them as short as possible by watching the LEDs below the
levelers (they should stay green) and the timing standard deviation (should be
as low as approx. 0.5 ms).
levelers (they should stay green).
For test purpose it is possible to run server and client on the same computer. For
this setup firstly start server and then the client. Type in 127.0.0.1 for the
IP address in the client.
this setup first start the server and then the client. Type in 127.0.0.1 for the
IP address in the client software.
EXTERNAL CODE: