WO2000038170A2

WO2000038170A2 - Font substitution system

Info

Publication number: WO2000038170A2
Application number: PCT/US1999/029302
Authority: WO
Inventors: Dennis Fleming
Original assignee: Powertv, Inc.
Priority date: 1998-12-18
Filing date: 1999-12-13
Publication date: 2000-06-29
Also published as: WO2000038170A3; KR20010093190A

Abstract

A method for displaying fonts on a graphics display comprising the steps of: extracting font information from a font transmission, comparing the font information with stored font information in a font database to select the corresponding font stored in the font database for display, and substituting an alternate font located in the font database for an unknown transmitted font by comparing the font information to the font database to select the alternate font for substitution which closely approximates the unknown transmitted font.

Description

FONT SUBSTITUTION SYSTEM ^#

BACKGROUND OF THE INVENTION

The present invention relates generally to an operating system for a multimedia system,

and more particularly to methods and apparatus for the storage and display of lettering or

fonts on a graphics display device such as a television.

Information service to the home is a new field, enabled by the availability of storage

and transmission technologies that can store and deliver data such as video and images at an

affordable cost. The once separate domains of television, computers, communications, and

entertainment are currently melding to form a new marketplace for interactive television.

A variety of players populate the emerging interactive television market. Authoring

tool developers provide environments for creating multimedia products that consumers

utilize. Developers use these and other tools to create multimedia content. Broadcasters and

interactive content providers market these products and other media across broadcast

networks. Manufacturers provide the hardware and operating system developers provide the

software that allows consumers to take advantage of these products and services from their

home televisions and multimedia systems.

In the new home multimedia systems, an encoded television signal is usually decoded

and formatted for display on a television screen by a device commonly referred to as a "set-

top terminal" or "box." Interactive digital set-top terminals provide an open platform for

developing and delivering interactive services and multimedia content to consumers across a

broadcast network. Such set-top terminals are equipped with numerous abilities including the

ability to display different typefaces or fonts as messages overlaid or superimposed on a

television screen. The set-top terminal performance is restricted by requirements such as ^"me

management of high data throughput, limited memory in a constrained consumer device, and

support for a secure environment drive. These requirements drive the decision to architect an

innovative operating system for use in set-top terminals to optimize the network and processing

capabilities of a digital set-top terminal support, ensuring a broad range applications and

services are provided.

SUMMARY OF THE INVENTION

Broadcasters frequently encode messages or advertisements in different typefaces,

fonts, or letters to be displayed and overlaid on a television screen. The fonts are designed

by the broadcasters to have a certain appearance to catch the eye of a viewer, for brand

recognition, or for any other application in which the appearance of a font is important. For

example, a well recognized trademark will have a certain letter or font style which is

recognized by consumers as a source indicator for a product. The trademark owner will

desire to have this font style reproduced as closely as possible on a television screen when

advertising their product. Presently, font images are incorporated as post-process fonts in

video signals displayed on a television screen. The post-process fonts are part of the picture

and are not transmitted as a separate signal.

Post-process fonts add complexity to the production of a video signal because an art

generation tool is needed to generate the fonts, photograph the fonts, and incorporate the

fonts as part of the picture in a video signal. Broadcasters today desire the ability to input

a message in their preferred font style, digitally transmit, and then reproduce the message

with the desired font style on a television screen via the set-top terminal. The problem which

occurs with this type of digitally encoded font information is that the font style transmitted by the broadcaster might not be recognized by the set-top terminal coupled to the television.

A set-top terminal has a limited amount of memory which may be utilized as a font style

database. If the transmitted font style is not included in the font style database, it will not be

displayed accurately, if at all.

The present invention incorporates an independent font engine in the set-top terminal

operating system which can approximate the appearance of unknown font styles. In the case

where a font style is unrecognized, the font engine will analyze the unknown font style and

match it to similar font styles contained in the font style database

The font style database is dynamic and can be purged and repopulated with new font

styles, depending on the frequency of use for specific font styles. The addition of font styles

to the font style database can be done through the transmission of font styles to the set-top

terminal. These stored font styles can then be referenced by messages with similar font

styles.

Further objects, features, and advantages of the invention will become apparent from

a consideration of the following description and the appended claims when taken in

connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a hardware diagram of an exemplary digital set-top terminal;

Figure 2 is a block diagram of the operating system, showing the font

substitution engine as one component thereof; and

Figure 3 is a detailed block diagram showing the components of the font

substitution engine of the invention. DETAILED DESCRIPTION ^J

The following description of the present invention is merely exemplary in nature and

is in no way intended to limit the invention or its uses. Moreover, the following description,

while depicting an operating system designed to reside on a conventional set-top terminal, is

intended to adequately teach one skilled in the art to make and use an operating system for a

variety of consumer multimedia clients including, but not limited to, intelligent televisions,

Internet terminals and advanced DVD players.

The font substitution engine of the invention is preferably embedded as a component

in a computer operating system residing in a set-top terminal, as will be described more fully

below. Although the font substitution engine is not limited to the set-top terminal environment,

it is useful in that environment. Accordingly, Figure 1 illustrates the basic components of a

digital set-top terminal. A basic understanding of the set-top terminal may be helpful in

understanding the font substitution engine of the invention.

Referring to Figure 1, the set-top terminal 10 is coupled to the cable and

telecommunications infrastructure 12 through a suitable cable 14. The set-top terminal is also

coupled through a second cable 16 to the television set 18. Communication between the

telecommunications infrastructure 12 and the set-top terminal 10 establishes a variety of

communications and program options available to the subscriber for interactive control and

participation in a way the licensing and charging is easily administered.

The incoming cable 14 may support a plurality of different channels. For purposes of

illustration, cable 14 has been shown as supplying three different logical channels: (a) a set of

analog TV channels, (b) a set of digital TV channels and (c) a set of data communication

channels. It will be appreciated that these are logical channel constructs; all three sets of

channels are typically carried on the same physical wire or fiber-optic cable. Thus the three separate channels shown in Figure 1 are for illustration purposes only. *

Conventionally, the analog and digital TV channels support one-way communication,

from the cable and telecommunications infrastructure 12 to the digital tuner 20. The data

communication channels are two-way channels, supporting bi-directional communication

between the infrastructure 12 and the tuner 20.

The various sets of channels supplied via cable 14 are distinguished by frequency.

Digital tuner 20 selects which frequency, and thus to which channel, the set-top terminal is

tuned. Analog TV channels are sent directly from tuner 20 to the multimedia compositor circuit

22. The compositor circuit formulates the RF signal supplied through cable 16 to the television

18. Typically the television is tuned to a pre-assigned channel to properly receive the RF signal

from compositor 22.

Digital TV channels are also sent to compositor 22, although they are first processed

through the additional circuitry illustrated at 24. Specifically, the digital TV signal is first

processed through the quadrature amplitude modulated (QAM) data link processor 26 and then

by the MPEG transport circuitry 29. The transport circuitry extracts the desired digital TV

program from the transport stream. It then separates the audio, video and data components,

which are routed to the video and audio decoders 30 and to the CPU ram 36. MPEG video and

MPEG audio are then separately processed by the circuitry 30.

Data communication, including control signals for messaging are separately processed

through the quaternary phase shift keying (QPSK) modem 32. The modem is coupled to the

central processing unit (CPU) 34, which has associated CPU RAM 36.

The multimedia compositor 22 generates a display image from video and audio input

streams and from CPU-generated media. It combines graphics and text, generated by

applications running in the digital set-top terminal, with full motion MPEG-2 or analog video. The composition of graphics and video includes translucent alpha-blending of the two, scaling

of motion video into a window, and the overlay of graphics and video. Similarly, the

multimedia compositor combines application audio with MPEG and analog broadcast audio,

mixing simultaneously networked and local sounds (either sampled or synthesized) into a single

signal.

In an interactive digital environment, QPSK channels provide transparent two-way

communications between the user and the content provider. Database queries to content

providers travel over these channels to provide users with a choice of interactive entertainment

options. While applications are running, these channels transmit user commands, such as play

video, pause, or fast-forward, to the content source. They also allow for the request and

delivery of graphics, fonts and other data and support purchasing of goods and services.

The presently preferred set-top terminal is bundled with an operating system whose

architecture is illustrated in Figure 2. Specifically, Figure 2 provides a high-level view of the

operating system components. The operating system consists of layers of interconnected

software modules designed to minimize redundancy and optimize multimedia processing in a

set-top terminal environment. Each module executes specific tasks concerning the

interpretation, transmission, and display of video and audio information as well as other types

of digital or analog information. The multitasking operating system is designed to address the

high-performance demands of media-centric, real-time applications being delivered through a

set-top terminal. The operating system provides an open, scalable platform for developing and

delivering multimedia content to consumers across broadcast and client/server networks. The

software architecture for the operating system is comprised of layers of interconnected modules

designed to minimize redundancy and optimize multimedia processing in an interactive,

network setting. A kernel and memory manager residing in the core layer 42 provide the bale

functionality needed to support an application. A fully preemptive, multithreaded, multitasking

kernel is designed to optimize both set-top memory footprint and processing speed. Since the

operating system will reside on consumer units, it has been designed to exist in a ROM-based

system with a very small footprint (e.g., 1MB), in addition, the kernel has also been created to

take advantage of 32-bit Reduced Instruction Set Computer (RISC) processors which enable

high-speed transmission, manipulation and display of complex media types. On the other hand,

a memory manager provides an efficient allocation scheme to enable the best performance from

limited memory resources. Because embedded processors are likely to be the mainstay of

consumer digital hardware implementations, the memory model requires little memory

management unit support. The core layer 42 also provides an integrated event system and a

standard set of ANSI C utility functions.

Built on top of the core layer 42 is an application support layer 116. This set of support

modules provides higher-level processing functions and application services. Application

management, session management, and tuner management are a few examples of these services.

At the highest application level 44, at least one application, referred to as a resident application

is always executing on a set-top terminal. The application level also provides the necessary

capabilities for authoring applications and for managing resources (e.g., the tuner) between the

resident application and other background applications residing on the set-top terminal.

The applications 44 are launched by the application manager 46 and thereafter

provide various user interactivity functions. Examples of applications 44 include on-screen

TV guide services, interactive advertising services, goods and services purchasing services,

internet web browsing and e-mail services, and the like. Although applications can be loaded

and run within the CPU RAM 36 (Fig. 1) they may also be resident on smartcards that are plugged into the set-top terminal to provide additional functionality. In this regard, the t-

top terminal may be provided with a suitable card interface jack 50 for receiving a suitable

credit card or smartcard 52.

Pertinent to the present invention is the font substitution engine that may be

implemented as part of the power draw component 40 that provides 2D imaging services and

graphics primitives used by the set of applications 44 running on the operating system.

The font substitution engine is designed primarily to allow the operating system to

display fonts that are not resident within the operating system. As discussed previously,

broadcasters frequently include messages or advertisements as fonts or letters to be displayed

and overlaid on a television screen. The fonts are designed by the broadcasters to have a

certain appearance, as in the case of a well recognized trademark. Broadcasters have the

ability to digitally transmit messages with specific font styles overlaid on a television screen

directly to a set-top terminal. Since there are numerous font styles which exist and the set-top

terminal has a limited amount of memory to be utilized in saving font styles, many

transmitted font styles will not be recognized by the set-top terminal 10, leading to

difficulties in the display of the font style. The font substituting engine of the present

invention provides a solution to this problem.

When an application requests a certain font to be displayed, the operating system

complies with the request, provided the font is resident within the system. If the font is not

resident, the font substitution engine applies a set of font substitution rules to supply a

substitute font. However, unlike conventional font substitution mechanisms, the font

substitution engine of the invention is font engine independent. Rather than store font

information in font engine-specific form (e.g. Postscript, Agfa, TrueType) the invention

stores font information as font style data. This font style data is stored in a font style database that the font substitution engine accesses to select the appropriate substitution font. *

The font style database stores font style attributes, such as point size, stroke weight,

style (roman, italic, bold), and proportional-fixed. These attributes define a font style in

sufficient detail for most on screen display applications to allow font substitution to be

performed quite efficiently. However, the font style database is not limited to these attributes.

Rather, the system permits additional attributes to be defined and added to the database

structure on the fly. Thus applications can define new font style attributes and these may be

added to the database structure. By way of example, an application could specify that a serif-

sans-serif attribute be added to the database. Thereafter, this application, or any other

application, may request serif and san-serif fonts and the font substitution engine is able to

comply.

The presently preferred font substitution engine architecture is shown in Figure 3.

The font substitution engine shown generally at 60. The font style database 62 stores font

style data as a collection of attributes. Illustrated at 64 in Figure 3 are the attributes: point

size, stroke weight, style (roman, italic, bold), and proportional-fixed. Other or different

attributes may also used. This information is used to select the correct font style from the

database 62. If the exact font style is stored in the database 62, then the font can be

reproduced in its precise font style. If the font style is not stored in the database 62, the font

most closely resembling the transmitted font style will be substituted.

The font substitution engine flexibly allows information about new fonts to be added

to the database. When information about a new font is added, the font registration module

66 extracts the font engine independent attributes (such as those listed above, or other

attributes specified by the user) and records them in database 62. In a typical system, font

style information will be stored in database 62 for all popularly encountered fonts. Because the system is font engine independent, the database can store style information about a

variety of otherwise incompatible fonts, including Postscript, Agfa and TrueType

The font substitution engine provides an engine interface 68 that applications may

access via the operating system to display fonts on the screen. If an application calls for a

font that is resident on the system, that font is automatically used for display. If the requested

font is not resident, the font request module 70 accesses the database 62 and determines the

font style attributes associated with the requested font. The engine then determines the

resident font that has the most similar attributes to the requested font using the substitution

rules 72 stored as part of the font request module 70. Using these rules, the resident font that

best matches the requested font is selected for display upon the screen.

The database 62 is dynamic and can be purged and repopulated with new font styles.

The transmitted font information can be stored in the database 62 for future use if it is

frequently used. Algorithms determine which font styles should be stored and which should

be purged.

It is to be understood that the invention is not limited to the exact construction

illustrated and described above, but that various changes and modifications may be made

without departing from the spirit and scope of the invention as defined in the following

claims.

Claims

I CLAIM ^

1. A method of displaying fonts on a graphics display comprising the steps of:

extracting font information from a font transmission;

comparing said font information with stored font information in a font

database to select the corresponding font stored in said font database for display; and

substituting an alternate font located in said font database for an unknown

transmitted font by comparing said font information to said font database to select said

alternate font for substitution which closely approximates said unknown transmitted font.

2. The method of claim 1, wherein said font information comprises font style

information.

3. The method of claim 2, wherein said font style information includes font size,

font weight, and font proportions.

4. The method of claim 1, wherein said font transmission is a digital

transmission.

5. The method of claim 1 further comprising the step of storing said extracted

font information in said font database.

6. The method of claim 5, further comprising the step of purging said font

database of infrequently used font styles.

7. The method of claim 1, further comprising the step of registering new font

styles in said font database.

8. The method of claim of claim 1 , further comprising the step of displaying a

font on a video device.

9. A font engine operating within a multimedia operating system comprising:

a font engine interface which receives transmitted font information;

a font registration system linked to said font engine interface to extract font

style information from said transmitted font information and store said extracted font style

information in a font style database and select a stored font style from said font style database

which matches said extracted font style information contained in said transmitted font

information for display on a graphics display; and

a font substitutor for selecting an alternate font style for display on said

graphics display when said transmitted font information contains an unknown font style.

10. The font engine of claim 9, wherein said extracted font style information

includes font size, font weight, and font proportions.

11. The font engine of claim 9, wherein said multimedia operating system is

contained in a set-top terminal.

12. The font engine of claim 9, wherein said font style database is dynamic.

13. The font engine of claim 9, wherein said alternate font style closely

approximates said unknown font style in appearance.

14. A font substituting system for a digital set-top terminal, said digital set-top

terminal used for delivering interactive services and multimedia content to a graphics display,

said font substituting system comprising:

an extractor which receives font information from a transmission, said font

information specifying the appearance of a font on said graphics display;

an abstractor which compares said transmitted font information to font

information stored in a font database to select a font to be displayed on said television screen

from said font database; and

a substitutor which replaces an unknown transmitted font with a similar font

stored in said font database for display on said television screen.

15. The font substituting system of claim 15, wherein said font database is

dynamic, whereby infrequently used fonts are purged and frequently used fonts are added.

16. The font substituting system of claim 15, wherein said transmitted font

information includes typeface, font size, font weight, and font proportions.

17. The font substituting system of claim 15, wherein said font information is

transmitted digitally.