Sun Microsystems MEDIACENTER 2.1 User Manual
Sun™ MediaCenter™ Server
Administrator’s Guide
Release 2.1
A Sun Microsystems, Inc. Business
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Part No.: 805-3194-10
Revision A, December 1997
1997 Sun Microsystems, Inc. All rights reserved.
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Contents
1. Introduction 1-1
1.1 Introduction 1-1
1.2 Sun MediaCenter Hardware 1-2
1.3 Sun MediaCenter Software 1-4
1.3.1 Media File System (MFS) 1-5
1.3.2 Media Stream Manager 1-7
1.3.3 Content Manager 1-8
1.3.4 Web-based Tools 1-8
1.4 Video Output Interfaces 1-8
1.4.1 ATM 1-9
1.4.2 LAN 1-9
1.5 Content Preparation and Loading 1-10
1.6 Server Management 1-11
1.7 Push Model 1-11
1.8 Design Benefits 1-12
2. Preparing and Loading Content 2-1
2.1 General MPEG Encoding Requirements 2-1
2.2 MPEG Encoding Requirements for Trick Play 2-2
Contents iii
2.3 Splice Points 2-3
2.3.1 Packet Boundary 2-3
2.3.2 closed_gop 2-4
2.3.3 payload_unit_start_indicator 2-4
2.3.4 adaptation_field_control 2-4
2.3.5 random_access_indicator 2-4
2.3.6 PCR_flag 2-4
2.4 Content Loading 2-5
2.5 References 2-7
3. Monitoring the Server 3-1
3.1 Overview 3-1
3.2 Using the WebAdmin Tool 3-2
3.2.1 Invoking the Tool 3-2
3.2.2 Common Page Elements 3-5
3.3 Resource Utilization 3-5
3.4 Streaming Videos 3-6
3.5 Copy Sessions 3-9
3.6 Disk Capacity 3-12
3.7 Troubleshooting 3-15
3.7.1 Disk Health 3-17
3.7.2 Console Log 3-18
3.7.3 Scheduler and Bitpump 3-20
4. Moving Content 4-1
4.1 Overview 4-1
4.2 Using CmTool 4-2
4.2.1 Invoking the Tool 4-2
4.2.2 Common Page Elements 4-5
4.3 Loading Content 4-5
iv Sun MediaCenter Server Administrator’s Guide • December 1997
4.4 Table of Contents Page 4-12
4.4.1 View Menu 4-13
4.4.2 Selected Menu 4-15
5. Sun MediaCenter Server Utilities 5-1
5.1 Setting a Title Access Control List 5-1
5.2 The smc_copy Utility 5-4
5.3 The smc_tar Utility 5-8
5.3.1 Syntax and Options 5-8
5.3.2 Content Loading 5-9
5.3.3 Copying Content 5-10
5.3.4 Remote Copying and Extraction 5-12
5.3.5 Examples 5-12
5.4 The smc_ls Utility 5-17
5.5 The smc_rm Utility 5-21
6. Sun MediaCenter Server
FTP Daemon 6-1
6.1 Keyword for Video-File Functions 6-3
6.2 Video-File Attributes 6-4
6.3 Video-File Commands 6-5
6.3.1 Listing Files 6-7
6.3.2 Moving Files 6-9
6.3.3 Renaming Files 6-13
6.3.4 Deleting Files 6-14
6.4 Loading Content with ftp 6-14
Contents v
7. Server Output Data Format 7-1
7.1 Introduction 7-1
7.2 ATM Encapsulation 7-2
7.2.1 MPEG-2 Transport Stream Packet Encapsulation 7-2
7.2.2 MPEG-2 Program Stream Packet Encapsulation 7-3
7.2.3 MPEG-1 System Stream Packet Encapsulation 7-3
7.2.4 Thomson Electronics Packet Encapsulation 7-3
7.2.5 MPEG-2 Encapsulation over Classical IP over AAL5 7-3
7.3 ATM Addressing 7-4
7.3.1 MPEG over AAL5 7-4
7.3.2 MPEG-2 over Classical IP over AAL5 7-4
7.4 Fast Ethernet Encapsulation 7-5
7.4.1 MPEG-2 Transport Stream Packet Encapsulation 7-6
7.4.2 MPEG-2 Program Stream Packet Encapsulation 7-7
7.4.3 MPEG-1 System Stream Packet Encapsulation 7-7
7.4.4 Thomson Electronics Encapsulation 7-7
7.5 Fast Ethernet Addressing 7-7
7.6 Specifying Encapsulation 7-8
7.7 Differences Among Different Types of Links 7-9
7.8 References 7-9
8. Administering MFS Disks 8-1
8.1 Monitoring MFS Disks 8-1
8.2 MFS Utilities 8-2
8.2.1 mfs df 8-2
8.2.2 mfs diskusg 8-4
8.2.3 mfs repair 8-5
8.2.4 mkmfs 8-8
8.3 Replacing a Failed Disk 8-10
vi Sun MediaCenter Server Administrator’s Guide • December 1997
9. Access Control Lists 9-1
9.1 ACL Files 9-1
9.2 Permissions 9-2
9.3 Server ACL 9-2
9.4 Player ACL 9-3
9.5 Title ACL 9-4
9.6 Session ACL 9-4
10. Troubleshooting 10-1
10.1 Symptoms and Possible Solutions/Workarounds 10-1
10.2 Error Messages 10-4
10.2.1 Server Console Messages 10-4
10.2.2 MFS Error Messages 10-5
A. Setting up the SNMP Agent A-1
A.1 The Sun MediaCenter Server MIB A-2
A.2 Enabling Management by Solstice Domain Manager A-6
A.3 Enabling Trap Handling A-9
B. Creating a Content Package B-1
B.1 Content Package B-2
B.2 The TOC File B-3
B.2.1 ContentObjects B-5
B.2.2 BitStreamObjects B-6
B.2.3 DataFileObjects B-7
B.3 Simplest Case TOC File B-8
B.4 TOC File for Large Files B-9
B.5 Index File Requirements B-10
B.5.1 Normal Play Time B-11
B.5.2 File Offset B-12
Contents vii
B.6 Tape Storage Format B-12
B.6.1 Tar Format B-12
B.6.2 Tapes B-14
B.7 Example B-14
B.8 References B-18
Glossary Glossary-1
Index Index-1
viii Sun MediaCenter Server Administrator’s Guide • December 1997
Preface
This document, the Sun MediaCenter Server Administrator’s Guide, tells you how to set
up, load content onto, and perform other administrative duties relevant to a Sun™
MediaCenter™ server. Specifically, this document describes:
■ at a high level, the hardware and software architecture of the Sun MediaCenter
server;
■ the content format required by the Sun MediaCenter server, plus utilities to load
and backup that content;
■ the format of the data output by the Sun MediaCenter server;
■ how to configure the SNMP agent shipped with the Sun MediaCenter for use
with Solstice™ Domain Manager™ or another SNMP-capable network manager.
Who Should Use This Book
This manual is intended for those who administer the Sun MediaCenter server.
We expect the reader to have experience in Solaris® network and system
administration and be familiar with maintenance issues related to servers.
Preface ix
The Sun MediaCenter Documentation
Suite
This manual is a companion to the Sun MediaCenter Server Installation and
Configuration Manual, the Sun MediaCenter Server Programmer ’s Guide and the Sun
MediaCenter UltraSPARC Hardware Manual. Together these manuals are
complementary of the hardware manuals shipped with the Sun products that make
up a Sun MediaCenter server. These documents include manuals for the server, for
the network interface (such as SunFastEthernet™ documentation), and the disk
subsystem.
How This Book Is Organized
Chapter 1 “Introduction,” introduces the Sun MediaCenter software at a high-level.
Chapter 2 “Preparing and Loading Content,” specifies the Sun MediaCenter
server ’s requirements for MPEG content. Trick-play format is defined here.
Chapter 3 “Monitoring the Server,” describes the WebAdmin tool, a Web-based
interface for monitoring a Sun MediaCenter server.
Chapter 4 “Moving Content,” describes the CmTool, a Web-based interface for
transferring content to a Sun MediaCenter server.
Chapter 5 “Sun MediaCenter Server Utilities,” describes the use of smc_copy and
smc_tar, used for moving content, as well as smc_ls and smc_rm.
Chapter 6 “Sun MediaCenter Server FTP Daemon,” tells you how to use ftp to
move content between a client machine and a Sun MediaCenter server.
Chapter 7 “Server Output Data Format,” describes the format of the data output by
the Sun MediaCenter server.
Chapter 8 “Administering MFS Disks,” tells you how to monitor disks in the Media
File System and how to deal with single and multiple disk failures.
Chapter 9 “Access Control Lists,” describes access control lists that you can create
and modify for Sun MediaCenter operations.
Chapter 10 “Troubleshooting,” presents some problems you might encounter in the
use of your server, along with possible solutions.
x Sun MediaCenter Server Administrator’s Guide • December 1997
Appendix A “Setting up the SNMP Agent,” tells you how to make use of the SNMP
agent that is shipped with the Sun MediaCenter server.
Appendix B “Creating a Content Package,” describes how to prepare content if you
are unable to use ftp for loading content.
The Glossary lists terms from the realm of video technology, as well as terms
specific to the Sun MediaCenter product.
What Typographic Changes Mean
The following table describes the typographic changes used in this book.
TABLE P-1 Typographic Conventions
Typeface or
Symbol Meaning Example
AaBbCc123 The names of commands, files,
and directories; on-screen
computer output
AaBbCc123
AaBbCc123 Command-line placeholder:
AaBbCc123 Book titles, new words or
What you type, contrasted with
on-screen computer output
replace with a real name or
value
terms, or words to be
emphasized
Edit your .login file.
Use ls -a to list all files.
machine_name% You have mail.
machine_name% su
Password:
To delete a file, type rm filename.
Read Chapter 6 in User’s Guide. These
are called class options.
You must be root to do this.
xi
Shell Prompts in Command Examples
The following table shows the default system prompt and superuser prompt for the
C shell, Bourne shell, and Korn shell.
TABLE P-2 Shell Prompts
Shell Prompt
C shell prompt machine_name%
C shell superuser prompt machine_name#
Bourne shell and Korn shell
prompt
Bourne shell and Korn shell
superuser prompt
$
#
xii Sun MediaCenter Server Administrator’s Guide • December 1997
CHAPTER
1
Introduction
Introduction page 1-1
Sun MediaCenter Hardware page 1-2
Sun MediaCenter Software page 1-4
Video Output Interfaces page 1-8
Content Preparation and Loading page 1-10
Server Management page 1-11
Push Model page 1-11
Design Benefits page 1-12
1.1 Introduction
The Sun MediaCenter server is a combination of standard server hardware and
special software that is optimized for and dedicated to the storage and delivery of
video streams. The special software includes:
■ a modified Solaris kernel;
■ modified network interface drivers, dedicated to continuous-media output;
■ a Media File System (MFS), optimized for the demands of the delivery of
isochronous bit streams;
■ a Media Stream Manager (MSM), which includes an RPC-based API, that
provides users access to the server;
1-1
■ a Content Manager (CM), which includes an RPC-based API that allows users to
move content between servers or between a server and a client.
■ Web-based tools that allow you to configure a Sun MediaCenter server, monitor
server operations, and transfer video content to a server.
The Sun MediaCenter server delivers MPEG bit streams at a constant bit rate. The
content of the streams are stored on an array of disks. The server guarantees that,
unless the server hardware fails, once a stream request is accepted, it will be
delivered at the specified constant bit rate until the stream ends or the server is told
to stop.
Using a Sun MediaCenter server, you can begin playing a stream within seconds
after storage of that stream on the server has started. This feature is called
“playthrough”.
The Sun MediaCenter server protects against single-disk failures by implementing a
parity mechanism similar to RAID Level 4 (Block-Interleaved Parity).
1.2 Sun MediaCenter Hardwar e
The Sun MediaCenter product line is built upon existing Sun hardware and
software. This provides you with excellent performance (especially in terms of cost
per stream) and flexibility in interfacing Sun MediaCenter servers to their
environment.
Each model of the Sun MediaCenter product line is designed to maximize input/
output throughput from the server’s disk subsystem through a network interface, to
an output device. Each model is equipped with a large amount of RAM, for
buffering streams and handling online content loading, and a large amount of disk
storage.
Within a disk subsystem, specific disk models are chosen for their appropriateness
for multimedia applications.
The Sun MediaCenter hardware architecture is shown in FIGURE 1-1.
1-2 Sun MediaCenter Server Administrator’s Guide • December 1997
Control
Content
Sun MediaCenter Server
Media Streams
(Fast Ethernet or ATM)
From tape,
network-accessible file,
or live source
Fast/Wide or Ultra
SCSI
Media
File System
Files
FIGURE 1-1 High-level Hardware Architecture
Content is loaded onto the Sun MediaCenter server via the server ’s Content
Manager, over a LAN or using 4- or 8-mm DAT tape. Video streams are controlled
through network interfaces distinct from the network interfaces used for video
output, using the Media Stream Manager (RPC-based) interface described in the Sun
MediaCenter Server Programmer’s Guide.
Chapter 1 Introduction 1-3
1.3 Sun MediaCenter Software
The Sun MediaCenter software has three major components, the Media File System
(MFS), the Media Stream Manager (MSM), and the Content Manager (CM). (In
addition to these, there are special network interface drivers, which are tightly
coupled with the MFS.) The relationship of these modules is illustrated in
FIGURE 1-2.
Java™ Applet Java™ Applet
Media Stream
Manager Client API
Sun MediaCenter
Server
RPC
Media Stream
Manager
Client
Content
Media Stream
Manager
Media File System
Network Drivers
Content
Manager
RPC
Content Manager
Client API
Content
Manager
User Space
Kernel Space
Video Streams
FIGURE 1-2 Sun MediaCenter Software Architecture
1-4 Sun MediaCenter Server Administrator’s Guide • December 1997
With the exception of the APIs for the MSM and CM, the workings of the server’s
software components are largely invisible to the user. This is particularly true of the
MFS, access to which is exclusively throughout the MSM and CM.
The Sun MediaCenter software offers the following features:
Guaranteed stream delivery rate
Once a stream is accepted for delivery, the server delivers the stream contents at a
guaranteed rate until the end of the stream content is reached, the server is asked
to stop playing the stream, or server hardware fails.
Independent streams
Delivered streams are independent: they can be stopped and started individually;
output streams might all be playing simultaneously from different portions of the
same content stream or from different content streams.
Online loading
The server maintains delivery of streams as the highest priority task, so that as
the server approaches its maximum bandwidth in stream delivery, any content
loading taking place will slow and, at some point, stop, until such time as the
server recovers sufficient resources to resume loading. (Note that you cannot load
content if the server is reading data from the parity disk, which occurs following
a disk failure.)
Playthrough
The server software supports a playthrough capability wherein a Sun
MediaCenter server can deliver streams from a title as that title is stored. A given
piece of content can be played from the server only five seconds after storage of it
has begun.
The following subsections describe the components of the Sun MediaCenter
software.
1.3.1 Media File System (MFS)
The MFS is designed to deliver multimedia data from an array of attached disks to
an output network. In addition to providing the foundation for all of the features
listed above, the file system supports:
Recovery from single-disk failures
The MFS will recover from a single disk failure after a small start-up interval (less
than 10 seconds). It uses a strategy similar to RAID-4. The number of content
disks for each parity disk varies with the disk subsystem used for a particular
server model.
Chapter 1 Introduction 1-5
Hot swappability
The MFS supports the replacement of a failed disk while the server continues to
deliver streams. Following disk replacement, you use a single command to restore
data from the parity disk to the new disk and return the server to normal
playback mode. The procedure for hot swapping a disk is described in Chapter 8,
“Administering MFS Disks.”
Efficient use of disk bandwidth
The file system is designed to extract a significant portion of the available disk
bandwidth (50-90%). Content is striped across the disk array.
The MFS compensates for thermal recalibration delays.
Efficient transfer from disk to output
The MFS is designed to transfer data from the disk array to the output network
with a minimum of processor involvement.
Large file and filesystem size
An MFS file can be as large as (2
31
2
files. In practice, file size and filesystem size are limited by available disk
64
)- 1 bytes in length; an MFS can contain up to
space rather than any limits imposed by the MFS.
High-resolution rate control
The MFS controls the rate of output so that any one output packet may be
delivered within the resolution of the underlying hardware/software system.
Random access
The controller of a stream may stop and start a stream at nearly arbitrary points.
The server maps these requests to the nearest content packet (for example, MPEG2 Transport Packet) boundary. This random access feature is used in trick play.
Section 2.2, “MPEG Encoding Requirements for Trick Play,” on page 2-2 for a
discussion of splice points in trick-play files.
Admission control
The MFS will not accept a request for a new stream that would cause it to fail to
deliver all its streams at the request data rate.
File locking
The MFS ensures that streams that are currently being played are not removed.
The MFS consists of five basic subsystems:
■ file system layout manager
The MFS layout manager allocates and deallocates disk blocks to content using
striping and parity algorithms.
1-6 Sun MediaCenter Server Administrator’s Guide • December 1997
■ scheduler
The scheduler sorts and schedules disk I/O, manages bit pump buffers, performs
admission control, and schedules output driver activity.
■ bit pump
The bit pump is responsible for allocating internal buffering and efficiently
transferring data between the disk and the output drivers using the internal
buffers. It is responsible for fine-grain scheduling and rate control of the output
driver. The bit pump is dependent on the particular output driver used, whether
it be for Fast Ethernet or ATM.
■ disk driver
The output driver is responsible for low-level output device management and
encapsulating outgoing data according to the rules of the output medium, and for
efficiently transferring data from the internal buffers to the output medium.
See Chapter 7 for a description of the format of output data.
■ output driver
The disk driver is responsible for efficiently transferring disk data to the fixed
internal buffers. It consists of a SCSI disk driver and a modified SCSI host adapter
driver.
The MFS components listed above are illustrated in FIGURE 1-3.
Media File System
Layout Manager
Scheduler
Bit Pump
Buffers
Disk
Driver
Output
Driver
FIGURE 1-3 Media File System Components
1.3.2 Media Stream Manager
The MSM controls the video streams stored in the MFS. The MSM implements a set
of procedures that interact with the MFS to allow you to stop, start, pause, and
resume video bit streams. A central notion of the MSM is the playlist, from which
titles can be played on a time-synchronized basis. Each playlist is associated with a
player, which can be passed among multiple clients.
Chapter 1 Introduction 1-7
The MSM’s primary interface is the MSM Client API, described in the Sun
MediaCenter Server Programmer’s Guide.
The MSM supports playthrough, trick play, and other features of the Media File
System.
1.3.3 Content Manager
The CM provides for the loading of content onto a Sun MediaCenter server. Server
requirements for content, such as Table of Contents files and index files (for trick
play) are handled transparently by the CM. The CM also supports the movement of
content between Sun MediaCenter servers and between a server and a client. This
capability provides for the backing up and restoring of video files.
The CM has a server-based set of RPCs and a SPARC client-based library, both
described in the Sun MediaCenter Server Programmer ’s Guide. Chapter 4 describes a
Web-based tool for moving content onto a Sun MediaCenter server. Chapter 5
presents a set of utilities based on CM. Chapter 6 describes the Sun MediaCenter
FTP daemon, which is also based on CM.
1.3.4 Web-based Tools
The following Web-based tools are provided with the Sun MediaCenter server
software:
■ The Configure utility allows you to configure a Sun MediaCenter server. This tool
is described in the Sun MediaCenter Installation and Configuration Manual .
■ WebAdmin allows you to monitor server operations. This tool is described in
Chapter 3.
■ CmTool allows you to transfer video content to a server. This tool is described in
Chapter 4.
1.4 Video Output Interfaces
Sun MediaCenter software is designed to output streams over ATM or Fast Ethernet,
using SunATM™ or SunFastEthernet™, respectively. With both types of output, the
streams are delivered at a constant bit rate; there is no dynamic flow control or error
recovery protocol. This is referred to as the “push” model of stream delivery and is
discussed in Section 1.7, “Push Model,” on page 1-11.
1-8 Sun MediaCenter Server Administrator’s Guide • December 1997
1.4.1 ATM
In an ATM environment, one or more Sun MediaCenter servers are directly
connected to an ATM switch via ATM host adapters. Digital video streams are sent
to clients using ATM virtual circuits.
FIGURE 1-4 Sun MediaCenter Servers in ATM Environment
1.4.2 LAN
In the LAN environment, each Sun MediaCenter server is connected to one highspeed 100BaseT subnetwork via one or more Fast Ethernet host adapters. Digital
video streams are sent to their destination(s) using LAN packets. Destination clients
can access the video streams by connecting directly to one of the 100BaseT networks.
Alternatively, the 100BaseT networks can be connected to an optional packetfiltering switch that routes to independent 10BaseT networks. This allows individual
destination clients to connect to a 10BaseT network without affecting the aggregate
bandwidth available.
Chapter 1 Introduction 1-9
FIGURE 1-5 Sun MediaCenter Servers in LAN environment
1.5 Content Preparation and Loading
The Sun MediaCenter software specifies a format for content, described in Chapter 2,
“Preparing and Loading Content.”
Sun MediaCenter software uses the Content Manager for storing video content on
the server. The Content Manager offers the following interfaces:
■ A set of RPCs that enable moving of content between local storage and a Sun
MediaCenter server. Also, there are RPCs to delete and rename content and to
manipulate access control lists.
■ A client library based on the RPCs described in the preceding bullet. This library
provides you the features of the RPCs and frees you from having to deal with
network programming.
■ CmTool, a Web-based interface for transferring video content onto a Sun
MediaCenter server.
■ A set of utilities based on the Content Manager. These include smc_tar,
smc_copy, and a Sun MediaCenter FTP daemon. In some cases, these utilities
automatically create the administrative files that support a bit stream.
Once content is stored in the MFS, you use the MSM to play it. The MSM supports
VCR-like functions, such as play, pause, fast-forward (at multiple speeds), and
reverse.
1-10 Sun MediaCenter Server Administrator’s Guide • December 1997
1.6 Server Management
An SNMP agent is provided is provided with the Sun MediaCenter software. This
agent includes the following MIB information:
■ current number of playing streams;
■ current aggregate bandwidth;
■ number of missed deadlines;
■ number and location of disk errors.
The SNMP agent also supports the following traps:
■ Missed_Deadline
■ Admission_Failed
■ Disk_Failure
See Appendix A for a description of and instructions for configuring the SNMP
agent.
1.7 Push Model
The Sun MediaCenter server implements the “push” model of bit stream delivery. In
this model, the server initiates and delivers bit streams over a network interface
dedicated to video output. On this interface, there is no “back channel” for decoderto-server flow control. The burden of staying within the time constraints of bit
streams is entirely on the server. On the receiving end, the decoder must be fast
enough to keep up with the server, but does not bear any responsibility for
maintaining timely delivery.
The push model differs from the “pull” model, in which the receiving device
engages a video server in a protocol for connection setup and bit-stream delivery.
Both server and receiver must be able to look inside the bit stream to interpret and,
possibly, take action, based on the contents of MPEG packets.
The push model has an advantage over the pull model in that receiving devices do
not require intelligence for communicating with the server. Receiving devices can be
simpler and less expensive than pull-model receivers.
Consistent with the push model, the Sun MediaCenter server’s supporting software,
including the MSM, reflects the one-way communication between the server and
receiving devices. For example, network interface drivers used for bit stream
Chapter 1 Introduction 1-11
delivery support output only. The MSM Client API has calls that allow you to
specify an ultimate destination, but do not, for example, allow you to set any
parameters on that destination, which would imply the ability of the receiver to
confirm a setting.
1.8 Design Benefits
The Sun MediaCenter server is more than simply a standard server with large
amounts of memory and disk space. It is the Sun MediaCenter software—the MFS in
combination with network drivers optimized for video output—that distinguishes
the Sun MediaCenter server from its standard counterpart. This software provides
the following advantages over a standard server:
■ A Sun MediaCenter server can guarantee a certain specified level of stream
delivery, with defined limits to jitter and drift. This means that, unless server
hardware fails, a Sun MediaCenter server will continue to deliver video bit
streams, up to its maximum output bandwidth, at the rate specified in those
streams.
■ Because the Sun MediaCenter server is dedicated to and optimized for video-bit-
stream delivery, the server can support more bit streams for the same amount of
hardware resources (memory, disk space, and network interfaces), as compared to
a standard server. This means that a Sun MediaCenter server has a lower cost per
stream than a comparably equipped standard server that is used as a video
server.
■ Because the MFS is tailored to high I/O bandwidth applications, the Sun
MediaCenter server can guarantee average-case disk I/O. Servers that rely on
standard file systems can guarantee only worst-case disk I/O. The MFS ensures
that whether users request different bit streams, up to maximum bandwidth, or
use up the maximum bandwidth with requests for the same bit stream, the
server ’s guarantee of timely delivery is not affected. With a file system not
optimized for video, certain user requests, such as multiple requests for the same
bit stream, are disruptive of server performance.
1-12 Sun MediaCenter Server Administrator’s Guide • December 1997
CHAPTER
2
Preparing and Loading Content
General MPEG Encoding Requirements page 2-1
MPEG Encoding Requirements for Trick Play page 2-2
Splice Points page 2-3
Content Loading page 2-5
References page 2-7
This chapter specifies what video content should consist of and how it should be
formatted, as required by the Sun MediaCenter software. It also provides guidelines
for content loading.
This chapter does not tell you how to encode content. The Sun MediaCenter server
has successfully stored and delivered content encoded on a variety of different
encoders, from a number of different vendors.
2.1 General MPEG Encoding Requirements
This section defines general MPEG encoding requirements. A subsequent section
defines additional constraints to the general requirements.
To play correctly on the Sun MediaCenter server, a bit stream must meet all of the
following requirements:
■ All bit streams in a content package must be encoded as either (1) MPEG-2
Transport Streams or Program Streams, conforming to the ISO/IEC 13818-1
standard, or (2) MPEG-1 System Streams, conforming to the ISO/IEC 11172-1
standard.
2-1
■ The timing information embedded in an MPEG file must exactly reflect the
constant bit rate encoded in the file. Specifically, the time differences between any
two consecutive PCR (SCR for Program Streams or MPEG-1 System Streams) time
stamps must exactly reflect the time required to play out the number of bytes
between the two PCRs (SCRs for Program Streams or MPEG-1 System Streams) at
the bit stream’s specified bit rate.
■ The bit stream must be encoded at constant bit rate, between 1.5 and 15 Mbit/sec.
You can encode a bit stream at any rate within this range.
■ Each bit stream must contain one and only one Program Association Table (PAT),
but these can be repeated as often as required. Multiple programs in one transport
stream is not supported.
■ Each bit stream must contain one and only one video stream.
■ For MPEG-2 Transport Streams, each MPEG-2 transport packet that contains the
Program Clock Reference (PCR) must occur in an even-numbered transport
packet, where the first transport packet in the stream is defined to be numbered 1,
and is odd. This is necessary to meet the ATM Forum MPEG-over-AAL5
requirement that, in the case where there are two MPEG-2 transport packets per
AAL5 packet, the PCR must be in the last transport packet in the AAL5 packet.
2.2 MPEG Encoding Requirements for Trick
Play
Trick play refers to the manipulation of video bit streams to create the effect of fast
forward and rewind, as found in conventional VCRs. To perform trick play, the Sun
MediaCenter server does not dynamically manipulate data within the normal-play
bit stream. Instead, the server switches from a normal-play stream to the appropriate
position in another bit stream that has the requested play speed and/or direction.
To enable trick play on the Sun MediaCenter server, you must provide a set of
distinct MPEG bit streams, beyond the bit stream that represents the movie at the
normal playback speed. These additional bit streams represent the content at several
speeds, in either the forward or reverse direction. If a content package does not
contain at least one additional bit stream beyond the bit stream for normal playback,
trick play functions are disabled.
All trick files must meet the following requirements:
■ All trick files must contain the identical video and audio PIDs as those of the file
at normal play speed.
■ All trick files must be encoded in a format (that is, MPEGTS, MPEGPS, or
MPEG1SYS) identical to the bit stream at normal play speed.
2-2 Sun MediaCenter Server Administrator’s Guide • December 1997
■ All trick files must be encoded at a bit rate that is less than or equal to the bit rate
of the normal-speed bit stream.
The Media Stream Manager supports the playing of trick play streams. See the
chapter on the Media Stream Manager Client API in the Sun MediaCenter Server
Programmer’s Guide for a discussion of how to play titles that have trick play streams.
2.3 Splice Points
To facilitate switching among multiple bit streams within a content package, all bit
streams must define convenient splice points. A splice point is a position in the bit
stream at which the server switches into or out of when a user switches from one
speed or direction to another. For optimum switching among streams, you should
specify splice point locations in an index file, the format for which is described in
Section B.5 “Index File Requirements” on page B-10.
Note – The Media Stream Manager switches among trick play streams and a normal
play stream even in the absence of an index file. However, if an index file is not
present, the Media Stream Manager performs positioning between streams by the
linear interpolation of bit rate over file size, which means that streams are entered
and exited at arbitrary points. This sort of stream switching causes problems for
some decoders. You should use trick play without an index file only if your decoder
is capable of resynchronizing and if artifacts are acceptable.
The frequency of the splice points within the bit streams in a content package should
reflect the latency you want for trick play functionality. More splice points mean
lower latency.
A splice point must have the characteristics described in the following subsections.
2.3.1 Packet Boundary
A splice point must occur on the boundary of the underlying packet. For example,
for the MPEGTS format, the splice point should occur on the MPEG-2 transport
packet boundary.
Chapter 2 Preparing and Loading Content 2-3
2.3.2 closed_gop
The closed_gop is a one-bit flag that indicates the nature of the predictions used in
the B-pictures immediately following the first coded I-frame following the group-ofpictures header. The closed_gop must be set to 1 to indicate that these B-pictures
have been encoded using only backward prediction.
2.3.3 payload_unit_start_indicator
For an MPEG-2 Transport Stream, the first MPEG-2 transport packet following a
splice point must have the payload_unit_start_indicator set, and the packet must
contain a payload.
2.3.4 adaptation_field_control
For an MPEG-2 Transport Stream, the first MPEG-2 transport packet following a
splice point must have the adaptation_field_control set to indicate an adaptation
field as well as payload (value of 11).
2.3.5 random_access_indicator
For an MPEG-2 Transport Stream, the first MPEG-2 transport packet following a
splice point must have the random_access_indicator set to 1.
2.3.6 PCR_flag
For an MPEG-2 Transport Stream, the first MPEG-2 transport packet following a
splice point must have the PCR_flag set to 1, and must contain the PCR value in the
adaptation field.
Note – The above requirements for splice points apply to the video stream. If the
bit stream contains audio, and/or other elementary streams, the requirements apply
to those streams as well.
2-4 Sun MediaCenter Server Administrator’s Guide • December 1997
2.4 Content Loading
The preferred method of storing content on a Sun MediaCenter server is to use the
Web-based CmTool. CmTool uses the Sun MediaCenter FTP daemon and the
Content Manager (CM), part of the Sun MediaCenter software, to store content. The
CM automatically extracts from MPEG content the information the server needs to
successfully store and play that content. See Chapter 4 for information on using the
CmTool interface.
The Sun MediaCenter software also offers the following alternatives for transferring
video files:
smc_tar
Can copy to or extract from a tape device. Takes a content package as input for
content loading. Copies between a tar device or a Unix File System (UFS) and
the MFS.
smc_copy
Takes a title name as input. Use from server to server. Can create a TOC file and
index files if none present. Copies between MFSs.
ftp in conjunction with the Sun MediaCenter FTP daemon
Requires only the smc: keyword. Works on any platform on which an ftp client
can run. Creates a TOC file and index files if none present. Copies between a local
file system and the MFS.
smc_tar and smc_copy are described in Chapter 5. See Chapter 6 for instructions
on the use of ftp with the Sun MediaCenter FTP daemon.
A file-transfer alternative beyond those listed here is to write a program to the
Content Manager (CM) API or CM Client API. These APIs are described in the Sun
MediaCenter Server Programmer’s Guide.
The Sun MediaCenter FTP daemon works with the most commonly-used MPEG
formats—MPEG-1 System Stream (MPEG1SYS) and MPEG-2 Transport Stream
(MPEGTS).
The following are circumstances in which you cannot use ftp to store content:
■ Your MPEG file is larger than 2.1 GB. Use smc_tar instead. With such large files,
you must create the correct segment clauses in the TOC file. See the description
of the TOC file in Appendix B. The 2.1 GB file size is a limitation of Solaris 2.4, not
the Sun MediaCenter server.
■ Your content is in a format other than MPEG1SYS or MPEGTS. If your stream is not
encoded in one of these formats, you must use smc_tar to load content.
Chapter 2 Preparing and Loading Content 2-5
■ The machine on which your content is stored does not have ftp client software.
■ For video file transfers from the server to a client machine, if your video file is
smaller or equal to 2.1 GB, use smc_copy or ftp. If the file is larger than 2.1 GB,
use smc_tar.
■ For video file transfers between Sun MediaCenter servers, use Cmtool or
smc_copy.
■ If you want to perform a “third-party” transfer, in which you invoke a command
on one machine to transfer video files between a second and a third machine, use
smc_copy.
■ To copy to or extract from a tape device, use smc_tar.
■ Both ftp and smc_tar are useful for backup and restore of video files.
If any of these circumstances applies to you, you must create a content package as
described in Appendix B, then use smc_tar to load your content. See Chapter 5 for
a description of smc_tar.
When you copy content to a Sun MediaCenter server (which includes the narrower
case of content loading), you, the copier, have certain access to that title that is not
available to other users. You use the smc_settacl utility to change access to the
copied title. See Section 5.1 “Setting a Title Access Control List” on page 5-1 an
explanation of setting permissions for copied titles.
A couple of points on content loading:
■ A Sun MediaCenter server can play streams while you are loading content.
■ You can begin to play a title seconds after you have started loading it onto the
server. This feature is called “playthrough” and is discussed in detail in the Sun
MediaCenter Server Programmer’s Guide.
■ For video formatted as MPEG-2 Transport Streams, Sun MediaCenter software
automatically generates index files for titles that contain trick play streams.
When storing content, free space in the UFS /var partition might be a consideration.
While the bulk of content storage is handled by the disk subsystem controlled by the
MFS, the MFS software uses space in /var for keeping track of MFS files.
Specifically, the MFS uses:
■ a small amount of space for TOC and index files (these are described in
Appendix B);
■ a fixed amount, 1500 bytes, for each MFS file;
■ one byte for every 10 minutes of play time in a title.
The last requirement is a function of play time, not encoding rate or MFS file length.
As examples of MFS space consumption in /var, consider that a two-hour MPEG-1
title consumes 73.5 KB; a 30-second title consumes 1800 bytes. Our testing has
shown free space of 10 MB on a Sun MediaCenter UltraSPARC to be adequate for a
set of titles that places an extremely high demand on /var space.
2-6 Sun MediaCenter Server Administrator’s Guide • December 1997
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