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Volker Fischer
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README
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README
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/******************************************************************************\
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* Copyright (c) 2004-2006
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* Copyright (c) 2004-2008
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*
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* Author(s):
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* Volker Fischer
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*
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* This program is free software; you can redistribute it and/or modify it under
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* the terms of the GNU General Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at your option) any later
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* Foundation; either version 2 of the License, or (at your option) any later
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* version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc.,
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* this program; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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\******************************************************************************/
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llcon
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-----
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Low-Latency Connection / client and server
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OBJECTIVES:
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The task is to build a client/server software to enable musicians to play together
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over the internet. Target internet connection is DSL with 256 kbps upstream and
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1 Mbit downstream. The server software must be located at a server with a very
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fast internet connection (at least 1 Mbps for up- and downstream).
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To get sufficient results, a sample rate of 24 kHz (mono channel) was chosen. An
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audio compression algorithm with very low delay is IMA-ADPCM (delay is just one
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sample). This gives a raw compressed audio data rate of 96 kbps.
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Target hardware setup at the client is stereo audio input signal with one channel
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is the instrument and the other channel is a microphone signal. On the microphne
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channel a reverberation effect can be applied (maybe at a later time other audio
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effects are added).
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MANUAL:
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For starting server type ./llcon -s
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Start the llcon server on a remote computer with fast internet access. Start the
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llcon client on your local computer and connect your sound card with your
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instrument/microphone and headphone and type in the IP address of the server.
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There are levelers for adjusting the sound card (in/out) and network buffer sizes.
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It seems that 2 blocks for network buffer is optimal choice. For the sound card
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buffer, try to make them as short as possible by watching the LEDs below the
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levelers (they should stay green) and the timing standard deviation (should be
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as low as approx. 0.5 ms).
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For test purpose it is possible to run server and client on the same computer. For
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this setup firstly start server and then the client. Type in 127.0.0.1 for the
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IP address in the client.
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EXTERNAL CODE:
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This code contains open source code from different sources. The developer(s) want
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to thank the developer of this code for making their efforts available under open
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source:
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- audio reverberation code: by Perry R. Cook and Gary P. Scavone, 1995 - 2004
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(taken from "The Synthesis ToolKit in C++ (STK)")
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- IMA-ADPCM: by Erik de Castro Lopo
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- some parts are taken from the project "Dream: a PC-based Digital Radio Mondiale
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(DRM) receiver" written by one of the llcon authors, Volker Fischer
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Low-Latency Connection / client and server (http://llcon.sourceforge.net)
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INTRODUCTION:
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The llcon software enables musicians to play together over the internet. The
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way it works is that there must be one server which collects the audio data
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from each client, mixes all together and sends the mix back to each client.
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The minimum internet connection speed at each client must be 256 kbps upstream
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and 1 Mbit downstream. The server software must be located at a server with a
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very fast internet connection (at least 1 Mbps for up- and downstream) and a
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very low ping time. To get satisfactory results, the ping time from the client
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computer to the server should not exceed 30 ms average and the network jitter
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should be as low as 2-5 ms (To get a low ping time on DSL connections, an
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extra option "DSL fast path" should be enabled by your internet provider).
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Technical details
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To get sufficient results, a sample rate of 24 kHz (mono channel) was chosen.
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The audio compression algorithm IMA-ADPCM with very low delay is used which
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results in a raw compressed audio data rate of 96 kbps. First tests showed
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that an upstream of 128 kbps is too slow for using the llcon software. At
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least 256 kbps upstream bandwidth is required.
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The llcon software package includes both, the server and the client
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functionality which can be selected by using command line arguments.
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MANUAL:
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For starting server type ./llcon -s
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Start the llcon server on a remote computer with fast internet access. Start the
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llcon client on your local computer and connect your sound card with your
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instrument/microphone and headphone and type in the IP address of the server.
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There are levelers for adjusting the sound card (in/out) and network buffer sizes.
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It seems that 2 blocks for network buffer is an optimal choice. For the sound card
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buffer, try to make them as short as possible by watching the LEDs below the
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levelers (they should stay green).
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For test purpose it is possible to run server and client on the same computer. For
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this setup first start the server and then the client. Type in 127.0.0.1 for the
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IP address in the client software.
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EXTERNAL CODE:
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This code contains open source code from different sources. The developer(s) want
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to thank the developer of this code for making their efforts available under open
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source:
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- audio reverberation code: by Perry R. Cook and Gary P. Scavone, 1995 - 2004
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(taken from "The Synthesis ToolKit in C++ (STK)")
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- IMA-ADPCM: by Erik de Castro Lopo
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- some parts are taken from the project "Dream: a PC-based Digital Radio Mondiale
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(DRM) receiver" written by one of the llcon authors, Volker Fischer
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