UltraGrid/ultragrid

UltraGrid - A High Definition Collaboratory

   Copyright (c) 2001-2004 University of Southern California 
   Copyright (c) 2003-2004 University of Glasgow
   All rights reserved.

   This software is distributed under license, see the file COPYRIGHT for
   full terms and conditions.


About UltraGrid

   UltraGrid is an experimental high-definition video teleconferencing
   system. It was developed by the University of Southern California's
   Information Sciences Institute, and by the Department of Computing
   Science at the University of Glasgow. The project aims to demonstrate
   high-quality video conferencing running over standard UDP/IP networks,
   and to investigate adaptive congestion control for multimedia systems.

   The contents of this directory are as follows:

   	COPYRIGHT	Full license terms and conditions
   	INSTALL		Installation instructions
	MODS		Change log and modification history
	README		This file
	VERSION		Version number of the UltraGrid system
	bin/		Compiled binaries
	src/		Source code for the UltraGrid system
	test/ 		Source code and binaries for test routines
	Makefile.in	Build script
	acconfig.h	"	"
	config.guess	"	"
	config.sub	"	"
	configure	"	"
	configure.in	"	"
	install-sh	"	"


Hardware and Software Requirements

   The UltraGrid software has been developed on Linux and FreeBSD, but
   should port to other Unix-like systems with relative ease (the main 
   difficulty will be in porting the video capture and audio routines,
   since there are few portable APIs in this area). We have no plans to
   port the system to Microsoft Windows at this time.

   The system depends on modified versions of Tcl-8.0 and Tk-8.0 which
   should be included in the distribution. It will not work correctly 
   with the standard Tcl/Uk versions.

   The system can use the Xvideo extension to the X window system for
   accelerated video display. Recent versions of XFree86 and the X.org
   server provide the necessary support, depending on the capabilities
   of your hardware.

   HDTV capture and playback using a DVS HDstationOEM card is supported
   on Linux provided the necessary hardware is installed and the SDK is
   present. We have tested with version 2.5p3b of the DVS SDK, which 
   should be installed in ../sdk2.5p3b. 
   
   Hosts used to capture and send high definition video need significant
   I/O bandwidth: the minimum requirement is a PC with dual 64 bit/66MHz
   PCI bus architecture (such as found on server-class motherboards).
   Systems which have the HDTV capture card and network interface on the
   same PCI bus will perform very poorly. 

   Hosts used to receive and display high definition content have similar
   requirements: if using a DVS HDstation card for display, it should be 
   located on a separate PCI bus to the network card. Note that display
   adaptors that connect to the AGP bus perform well, since this is 
   separate to the PCI bus used for the network card.


Using the UltraGrid System

   The file INSTALL gives instructions for building the UltraGrid system. 
   Once the system has been built, the "uv" binary will be present. This
   can be invoked as follows:

   	uv -d <display_device> -m <mtu> hostname	(on the receiver)
	uv -t <capture_device> -m <mtu> -f <fps> hostname (on the sender)

   The <display_device> is one of "hdtv" for the DVS HDstation display
   card, "x11" for display using the X Window System and "xv" for display
   using the X Window System with the Xvideo extension (the "xv" display
   type provides better performance than "x11" if your hardware supports
   the Xvideo extension). 

   The <capture_device> is one of "hdtv" for the DVS HDstation capture
   card, or "testcard" for a static test image.

   The <mtu> specifies the maximum transfer unit of the network path from
   sender to receiver (the default MTU is 1500 octets, suitable for use on
   standard Ethernets). This parameter allows the application to make use
   of networks with larger MTU, for example gigabit Ethernet using jumbo
   frames. 

   The desired video framerate is specified by the <fps> parameter. The
   default, if not specified, is 60 frames per second.

   As an example, if a user on host "ormal" wishes to send video captured
   using a DVS HDstation card at 60 frames per second to another user on
   host "curtis" with a display using the Xv driver, then the user on host
   "ormal" would run:

   	uv -t hdtv -f 60 curtis

   while the user on "curtis" would run:

   	uv -d xv ormal

   The system requires access to UDP ports 5004 and 5005: you should open
   these ports on any firewall on the network path. High definition video
   formats require approximately 1 gigabit per second of network capacity.
   An automatic cutoff will operate, shutting down the system, if network
   congestion is detected.


Performance Tuning: Network

   To achieve optimum performance with high definition video, it may be
   necessary to tune your system's network parameters to more aggressive
   values than used by default.  

   A key factor affecting performance is the path MTU. It is unlikely that
   the system will sustain gigabit rates with the 1500 octet Ethernet MTU. 
   If using a gigabit Ethernet you may be able to improve performance by
   setting an 8192 octet MTU on the interface, provided all intermediate
   hops on the path from sender to receiver support the large MTU. 

   UltraGrid attempts to increase the UDP receive socket buffer from the
   default value (typically 64 kilobytes) to 2 megabytes. If successful,
   this will make the system more robust to scheduling variations and
   better able to accept bursty packet arrivals. If you see the message:

	WARNING: Unable to increase UDP recvbuffer

   when starting the application, this means that the operating system did
   not allow such a large buffer to be configured. On FreeBSD, the maximum
   buffer that may be configured can be set using the "kern.ipc.maxsockbuf"
   sysctl, for example:

   	sysctl kern.ipc.maxsockbuf=2621440

   Other operating systems may allow tuning of the maximum UDP buffer size
   in different ways.

   Interrupt processing load on the receiver host may be significant when
   running at high rates. Depending on your network interface hardware it
   may be possible to coalesce interrupts to reduce this load, although
   the settings to do this are highly driver dependent. On FreeBSD, the
   use of network device polling may also help performance: see the man
   page for "polling" in section 4 of the manual.

   In many cases, the performance of your network interface card may be
   limited by host bus performance (this is particularly an issue at high
   rates, for example when using HDTV format video).


Performance Tuning: Display devices

   If using a DVS HDstation card as a display device ("-d hdtv"), the
   key factor limiting performance is PCI bus contention. Ensure that
   the HDstation card is on a separate PCI bus to the network card --
   this typically requires a server class motherboard. On Linux, the
   PCI bus topology can be displayed using "lspci-tv", for example:

	[root@ormal root]# lspci -tv
	-+-[03]---06.0  Xilinx, Inc.: Unknown device d150
	 +-[01]-+-02.0-[02]--+-04.0  Adaptec 7899P
	 |      |            \-04.1  Adaptec 7899P
	 |      \-0e.0  3Com Corporation 3c985 1000BaseSX
	 \-[00]-+-00.0  ServerWorks CNB20HE
		+-00.1  ServerWorks CNB20HE
		+-00.2  ServerWorks: Unknown device 0006
		+-00.3  ServerWorks: Unknown device 0006
		+-04.0  Intel Corporation 82557 [Ethernet Pro 100]
		+-0e.0  ATI Technologies Inc Rage XL
		+-0f.0  ServerWorks OSB4
		\-0f.1  ServerWorks: Unknown device 0211
	[root@ormal root]# 

   showing an HDstation card on PCI bus [03] (the card shows as a Xilinx
   device) and a gigabit Ethernet card on PCI bus [02] (the 3Com entry).

   If using the X window system display routines ("-d x11"), performance
   will be poor. Performance of the conversion from native YUV format to 
   the RGB display format is limited by the memory bandwidth of the CPU.
   An implementation using SIMD instructions (e.g. MMX, AltiVec) would 
   be significantly faster than the current software implementation.
   Contributions of code are solicited.

   If using the X window system display routines with Xvideo extensions
   ("-d xv") performance should be good, although this depends on the
   quality of the display drivers. There is little tuning that can be
   performed, short of changing graphics card or updating the version
   of the X window system on your host.


Performance Tuning: Other Factors

   The UltraGrid system will attempt to enable POSIX real-time scheduling
   to improve performance.  If you see the message:

	WARNING: Unable to set real-time scheduling

   when starting the application, this means that the operating system did
   not permit it to enable real-time scheduling. The application will run,
   but with reduced performance. The most likely reason for failure to set
   realtime scheduling is that the application has insufficient privilege:
   it should either be run by root, or be made setuid root. A similar
   message:

   	WARNING: System does not support real-time scheduling

   indicates that your operating system does not support POSIX real-time
   scheduling. The application will still run, but performance may be less
   than desired.

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