WO2010132994A1

WO2010132994A1 - Improved data handling for modular display systems

Info

Publication number: WO2010132994A1
Application number: PCT/CA2010/000768
Authority: WO
Inventors: Graham Murdoch; Leonid Mordoukhovski; Cheng Qian
Original assignee: Graham Murdoch; Leonid Mordoukhovski; Cheng Qian
Priority date: 2009-05-21
Filing date: 2010-05-20
Publication date: 2010-11-25
Also published as: CA2762363A1

Abstract

A modular display system is provided that incorporates video compression for the efficient transmission of video or image data. Each module within a modular display system includes a codec, either in hardware or software, to decompress an image or video prior to displaying the image or video. By including a codec for the decompression of image or video data, the system enables the efficient transmission of high-quality image or data files with a lower bit rate transmission system. In a preferred embodiment, a wavelet-based codec is employed to enable spatial subdivision of a compressed image or video file prior to transmission to the display modules forming the modular display.

Description

IMPROVED DATA HANDLING FOR MODULAR DISPLAY

SYSTEMS

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 61/213,264, titled "COMPRESSION-BASED MODULAR DISPLAYS AND SYSTEMS" and filed on May 21^st, 2009, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to video display systems, and more particularly relates to modular and large scale video display systems.

BACKGROUND OF THE INVENTION Large scale video display applications have become increasingly popular for outdoor and indoor media applications. Due to their brightness, energy efficiency, and longevity, light emitting diodes (LEDs) have increasingly been incorporated into large-scale video display applications. In particular, signs and billboards displaying static or video images are now often designed with LED systems. Large scale display systems suffer from numerous drawbacks when made in a single piece, including a loss of manufacturability, serviceability, and design flexibility when custom sizes are required. Improvements that overcome many of the aforementioned problems were recently disclosed in US Patent Application US2009/000913 (McKenchnie et al.) and PCT Application WO99/41732 (Matthies et al.), which disclose LED display systems involving a tiled or modular design. Such modular display systems overcome the need to provide a single bulky system and enable the system to be assembled and maintained at low cost.

While these .modular systems address many of the known problems with traditional large single-component displays and signs, they are often poorly suited to the transmission of video signals, particularly high-bandwidth video formats such as high-definition television (HDTV). Specifically, in order for a modular display system to rapidly receive and display graphics such as standard or high-definition video, it is typically necessary to transmit large amounts of data to each of the display modules in a short period of time. The bit rate is typically very high, often reaching into the hundreds of Mbps. For large format signage, required data rates can be particularly large and often exceed the available bandwidth of typical data transmission systems. High bandwidth data distribution networks, often involving numerous data distribution nodes, are therefore necessary to deliver raw data to display modules. The requirements for high bandwidth distribution networks leads to system complexity and unreliability due to the number of physical processors, conductors and connectors required to quickly deliver large amounts of data. Furthermore, in the case of video display on modular systems, data rates are such that many wired and wireless data transmission can become impractical. In particular, for wireless networks, tradeoffs exist between data rate, reliability and range. In addition, with higher bit rates (which typically employ higher frequency radio waves), the radiation is more directional, requiring more line-of sight, which can interfere with normal operation. The use of powerline communication and wireless communication for modular systems is desirable due to the elimination of additional data connectors and associated engineering requirements such as environmental sealing, as well as ease of construction. Unfortunately, for power line data distribution, in which data is delivered over power lines, bit rates under 100 Mbps are typical and cannot support many video applications..

SUMMARY OF THE INVENTION

The aforementioned problems are overcome by incorporating video compression into modular display systems for the efficient transmission of video or image data. Each module within a modular display system is includes a codec, either in hardware or software, to decompress an image or video prior to displaying the image or video on an array of display elements. By including a codec for the decompression of image or video data, the system enables the efficient transmission of high-quality image or data files with a lower bit rate transmission system.

In a first aspect, there is provided a display module for use in a modular display system, comprising: a display subsystem comprising an array of display elements; a control system comprising an interface for receiving compressed image data, a processor and a codec for decompressing the compressed image data, and a display driver for driving the display elements to display the decompressed image data; and an external connection means for providing electrical power to the display module. The display module preferably further comprises a unique address for identifying a relative spatial location of the display module in a modular display system. The codec may reside in software or hardware, and may be a wavelet-based codec. The interface for receiving compressed image data may comprise one of a wireless receiver and a wireless transceiver, or may be selected from the group consisting of a power-line receiver, a power-line modem, and power-line transceiver.

The display module preferably comprises a weatherproofed housing.

In another aspect, there is provided a modular display system for displaying image data, comprising: a plurality of display modules, wherein each display module comprises: a display subsystem comprising an array of display elements; a control system comprising an interface for receiving compressed image data, a processor and a codec for decompressing the compressed image data, and a display driver for driving the display elements to display the decompressed image data; and an external connection means for providing electrical power to the display module; means for mounting the display modules in a desired spatial arrangement; and a primary controller comprising an interface for transmitting the compressed image data to the plurality of display modules. The plurality of display modules may be arranged to display one of a single composite image and a single composite video. The codec may resides in software or hardware, and may be a wavelet-based codec. A control system of a given display module preferably comprises a unique address for identifying a relative spatial location of the given display module in the modular display system.

The interface for receiving compressed image data may comprise one of a wireless receiver and a wireless transceiver, and the interface for transmitting the compressed image data may comprise one of a wireless receiver and a wireless transceiver. Alternately, the interface for receiving compressed image data may be selected from the group consisting of a power-line receiver, power-line modem and power-line transceiver and the interface for transmitting the compressed image data may be selected from the group consisting of a power-line transmitter, power-line modem and power-line transceiver.

The primary controller may further comprise a processor and a codec for compressing image data prior to transmitting the image data to the display modules. The primary controller may transmit the compressed data in a multicast format to the display modules. Alternatively, the primary controller may comprises a processor programmed to spatially segment the image data, correlate the spatially segmented image data with the unique addresses of the display modules, compress the spatially segmented image data, and transmit the spatially segmented and compressed image data to the display modules according to the unique addresses. The primary controller may comprise a wireless router providing wireless access to one or more users. In yet another embodiment, there is provided a method for displaying image data on a display module within a modular display system, the display module comprising: a display subsystem comprising an array of display elements; a control system comprising an interface for receiving compressed image data, a processor and a codec for decompressing the compressed image data, and a display driver for driving the display elements to display the decompressed image data; and an external connection means for providing electrical power to the display module; the method comprising the steps of: receiving compressed image data transmitted by a primary controller; processing the compressed image data with the processor and codec to obtain decompressed image data; and providing the decompressed image data to the display driver for driving the display subsystem to display the decompressed image data.

The compressed image data is preferably transmitted and received wirelessly, and the display module preferably further comprises a unique address for identifying a relative spatial location of the display module in the modular display system. The compressed image data may be broadcasted to a plurality of display modules by the primary controller, and the processor may further processes the decompressed image data to obtain a spatial subset of the decompressed image data for display on the display subsystem according to the unique address. The processor preferably deletes decompressed image data relating to other addresses prior to providing the decompressed image data to the display driver.

The compressed image data may pertain to a spatial subset of the image data, wherein the spatial subset corresponds to a spatial location and size of the display module, and wherein the primary controller transmits the compressed image data to the display module according to the unique address. The primary controller preferably further comprises spatial calibration data associating the unique address with a spatial location of the display module, and a processor and a codec for spatially segmenting the image data based on the spatial calibration data and compressing the spatially segmented image data. The primary controller may further comprise a processor for modifying a property of the image prior to compressing and transmitting the image data, wherein the property is selected from the group consisting of resolution, image quality, bit rate, and YCbCr component sampling.

A further understanding of the functional and advantageous aspects of the invention can be realized by reference to the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present invention are described with reference to the attached figures, wherein: Figure 1 shows a schematic of a control subsystem in which the codec resides in software.

Figure 2 shows a schematic of a control subsystem in which the codec is provided as a separate component. Figure 3 shows a broadcast transmission scheme in which the compressed image or video data is broadcasted to all display modules.

Figure 4 shows a transmission scheme in which an image or video file is segmented into individual files and transmitted to specific display modules.

DETAILED DESCRIPTION OF THE INVENTION Generally speaking, the systems described herein are directed to compression-based data handling systems for modular displays. As required, embodiments of the present invention are disclosed herein. However, the disclosed embodiments are merely exemplary, and it should be understood that the invention may be embodied in many various and alternative forms. The Figures are not to scale and some features may be exaggerated or minimized to show details of particular elements while related elements may have been eliminated to prevent obscuring novel aspects. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention. For purposes of teaching and not limitation, the illustrated embodiments are directed to compression-based data handling systems and methods for modular displays. As used herein, the terms, "comprises" and "comprising" are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in this specification including claims, the terms, "comprises" and "comprising" and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.

As used herein, the terms "about" and "approximately, when used in conjunction with ranges of dimensions of particles, compositions of mixtures or other physical properties or characteristics, is meant to cover slight variations that may exist in the upper and lower limits of the ranges of dimensions so as to not exclude embodiments where on average most of the dimensions are satisfied but where statistically dimensions may exist outside this region. It is not the intention to exclude embodiments such as these from the present invention.

As used herein, the coordinating conjunction "and/or" is meant to be a selection between a logical disjunction and a logical conjunction of the adjacent words, phrases, or clauses. Specifically, the phrase "X and/or Y" is meant to be interpreted as "one or both of X and Y" wherein X and Y are any word, phrase, or clause.

Embodiments of the present invention overcome the limitations in prior art modular display systems by providing systems and methods that utilize compression for efficient data handling and transmission. Compression involves the use of digital encoding and decoding schemes to shrink an original image or video file to a fraction of its original size by reducing redundancy within the image. The compressed file not only consumes significantly less memory, but it can also be easily transmitted over transmission media with limited bandwidth. Compression can either be lossy, in which some of the original fidelity of the image or video is lost, or may be lossless, in which the original image or file is completely recovered after the decoding step.

All compression methods employ a codec to perform the compression and decompression of an image or video. A codec may be a piece of hardware, such as a dedicated microprocessor, or alternatively may reside in software. Codecs are usually standardized and deployed across a wide array of platforms. Most codecs that are presently used involve some form of lossy compression. For example, DVD uses the MPEG-2 codec for compression, which is a lossy codec with a high compression ratio. Encoding and decoding methods such as MPEG2 typically spatially segment images or videos into regions called macroblocks, and perform compression and decompression on these macroblocks separately. There exists a tradeoff between compression ratio, image quality, and the number of macroblocks used in the codec. Specifically, image quality and compression ratios are reduced as more macroblocks are used. For instance, if macroblocks are made the size of single pixels, no compression advantage is achieved.

In a preferred embodiment, a display module for use in a modular display system includes a codec for the decompression of compressed video. Each module in the display system preferably includes two main components: a display subsystem and a control subsystem. The display subsystem comprises an array of display elements arranged on a surface. The display elements may comprise any display technologies known in the art, including, but not limited to, LEDs, organic LEDs, liquid crystal displays, plasma displays, e-ink displays, phonic crystal displays, polymer light emitting diodes, incandescent lights, fluorescent lights, laser diodes, phosphorescent lights and electroluminescent displays. Preferably, each pixel element comprises three light emitting elements that emit red, green and blue light. The array of display elements forming the display subsystem is controlled by the control subsystem. The control subsystem comprises all of the electronics needed to receive the image or video data, buffer incoming data, decompress or decode the data with a codec, process the decoded data, and furthermore comprises display element drivers to drive appropriate display elements to display the required image. The codec may be software executed by a processor, or a separate hardware decoder communicating with the processor (e.g. an FPGA may be programmed to act as a codec). The data decompression can be done simultaneous to playback, or can be done prior to playback. In the later case, data sent to a module would be decompressed by the codec and stored in its raw form for playback later. Alternatively, and preferably, because each module represents only a fraction of the display area in a modular system, any data irrelevant to a given module would preferably be deleted immediately after or during decompression and only relevant data would be stored. The control subsystem and the display system are contained within a housing that includes an external connection for providing power to the display module. The external connection may further provide image or video data to the display module. The housing is preferably weatherproofed using gaskets and/or other sealing materials known in the art, such as silicone. The housing may include a transparent window for protecting the display subsystem. The housing may further comprise an array of lenses and/or louvers to further protect the pixel elements and/or improve the quality of the displayed image. Additional configurations for mounting the subsystems making up the display modules are disclosed in

U.S. Patent Application No. 11/773,569, titled "Wirelessly Controlled Light Emitting Elements", and International Patent Application No. PCT/US99/03374, titled "Tiled Electronic Display Structure", both of which are incorporated herein by reference in their entirety. A modular display system is formed by combining two or more display modules to form a composite image. The display modules may be supported on a frame having a surface that provides data and/or power connections to the modules. In this embodiment, the external connection is provided in a rear planar surface of the housing. In a preferred embodiment, the connection providing power to the display modules comprises contact pads disposed on the rear surface of the display module, which contact locations on a conductive grid formed on the frame supporting the display modules. The conductive grid provides power connections to all display modules and is connected to a main power supply. Preferably, the grid comprises a horizontal or vertical array of parallel spaced conductive strips, with at least one strip of each polarity passing behind each display module, with modules within a given row or column connected in parallel. The contact pads are preferably raised to ensure that a conductive connection is achieved. In order to achieve a thin and lightweight form factor, the conductive grid is preferably provided in the form of flattened cables. Alternatively, the conductive grid may mechanically support the display modules directly. In this embodiment, the conductive grid is supported by an outer frame and a back substrate or mounting surface is not needed to support the grid. The grid is optionally supported by additional non-conductive cross-pieces connected to the outer frame, with cross-pieces preferably arranged orthogonally to the conductive grid.

In a preferred embodiment, the connections between the contact pads and the conductive grid are facilitated by an elastic or detent member, to ensure that a connection is maintained after the display module is physically connected and supported by the frame. Furthermore, the inclusion of an elastic member provides direct contact when the modular display system is subjected to vibrations, or when the physically connection of a display to the frame varies over time due to the loosening of fasteners. The elastic member may comprise an insulating member that biases the conductive pads against the conductive grid or may be formed directly into the structure of the contact pads.

In another embodiment, the connection provides the dual function of providing power to each display module and also physically connecting each display module to the supporting frame. Preferably, the connection also mechanically connects the conductive grid to the frame.

Alternatively, the display modules may be connected to each other by connections provided in the side of each housing. For example, each of the sides of the housing may include male and female connectors for connecting to adjacent display modules, where the male connector is movable between a recessed position and an external connection position. Accordingly, when connecting a given display module to any of four surrounding display modules, a single side may be selected for connection by moving the appropriate male connection to its external connection position. One or more external connectors (i.e. pair of male and female connectors) may be provided on each side for providing connections for data and/or power. Data and/or power is provided externally from an external power source or primary controller by connecting the external power source or primary controller to a display module housed on the perimeter of the modular display system.

In a preferred embodiment, the control system detects which side of a module is connected to a neighbouring display module. Accordingly, this information may be used, either by communicating the information to all display modules or to the primary controller, to determine the spatial ordering of the display modules within the modular display system. The modular display system may therefore automatically determine which part of a global image or video is to be displayed on a given display module. The control subsystem is contained within the housing and is preferably provided on one or more circuit boards that may be physically connected to the rear portion of the display surface. In some embodiments, components of the control subsystem, such as display element drivers, current limiting devices such as fuses, or wireless antennas, receivers or transceivers, may be preferably located on the front portion of the display surface adjacent to or between light emitters.

As previously noted, the control system includes all of the electronics needed to receive the image or video data, decompress or decode the data with a codec, process the decoded data, and display the required image by driving the appropriate display elements. Accordingly, the control system may include all or any of the following: an interface for receiving compressed image or video data, a hardware and/or software codec for decoding image or video data, at least one processor for processing the image or video data, one or more display element drivers, a controller for receiving or providing a synchronization signal such as a clock, memory to store received image or video data in a compressed or uncompressed format, memory to store calibration data relating to the calibration of individual pixel elements relative to other pixel elements on the same display module and/or other display modules forming the display system, a controller to communicate diagnostic or status information to a primary controller providing the image or video data, power supply, and power regulation. The processors may include a microcontroller, a central processing unit, an embedded processor, a digital signal controller, an embedded digital signal processor, a field programmable gate array or integrated circuit capable of performing the necessary data decompression and/or data handling operations. The interface may comprise any communications interface for receiving image data, including, but not limited to, a serial or parallel port, wireless receiver or transceiver, power line receiver or transceiver, USB port, FireWire port, Ethernet port, ATA/IDE interface, SCSI interface and PCI interface. A real time clock oscillator may be provided on each module to maintain mutual synchronization of the operations performed on each module. To set initial time or counter values, or to periodically reset the current time or counter on each module to the desired value ssynchronization signals may be provided by the primary controller or one or more modules. Periodic resynchronization is needed to correct for clock drift.

An exemplary embodiment of a control subsystem 10 is shown in Figure 1. The image or video data is received by a transceiver 12 incorporated into the display module and fed to a processor 14. In the embodiment shown in Figure 1 , data is transmitted wirelessly by the primary controller and received by a wireless receiver or transceiver within the control subsystem. The data stream may include compressed or encoded data in addition to uncompressed or unencoded data. The processor includes a codec 16 that is provided in software. Compressed data or decompressed data may be temporarily stored in a memory unit

18. Uncompressed image or video data is sent to a display controller or display element driver 22, which provides the appropriate current or voltage to drive individual pixel elements 24. Alternatively, the codec may reside in the separate physical processor 26, as shown in Figure 2. Each module control system preferably includes an identifier such as an address that enables the display module to be uniquely addressed by the primary controller. This enables the primary controller to provide information to each display module regarding the subset of the main image or video that that a given display module is to display, or alternatively delivers a specific subset of the full image or video data to a given display module, where the subset relates to the portion of the data or image that the display module is to display.

The control system within each module and the primary controller are preferably capable of bidirectional data transfer or communication.

This supports transmitting diagnostic or status information from the display modules to a primary controller. The modules also preferably receive other forms of data besides image or video data, such as calibration data and firmware upgrades. The control subsystems may also be employed to provide inter-module communication, for example to distribute synchronization or spatial configuration information between display modules forming the modular display system.

The connection for receiving the data signal may be a direct data connection such as Ethernet and serial busses. Alternatively, power line communication may be employed, in which the data signal is provided as a modulation on the power line voltage. Since power line data distribution typically involves data rates under 100 Mbps, data compression is required for high quality transmission of digital media. Accordingly, the system supports the distribution of high-quality video by power-line communication using the aforementioned compression methods. In a preferred embodiment, power-line communication is provided locally by enabling the primary controller to connect to the power line powering the modular display system (e.g. using a power line modem, transmitter or transceiver), with each display module control subsystem including a power-line communication receiver for receiving the data stream provided over the power line (such as a power line modem, receiver or transceiver).

In a preferred embodiment, a wireless receiver is incorporated into the control subsystem to receive the image or video data. In this embodiment, a separate wireless transmitter resides in the primary controller for transmitting the image or video data. Preferably, the wireless transmission system formed between the display modules and the primary controller is bidirectional, in which case the aforementioned receivers and transmitter would be replaced with wireless transceivers.

As described above, the image or video data transmitted to the display modules by the primary controller is in a compressed format, which enables much lower bit rates and supports the transmission of video formats such as high-definition video over multiple transmission methods including wireless transmission. In one embodiment, the image or video data is compressed by the primary controller. In another embodiment, the image or video data is provided to the primary controller in a compressed format and is directly transmitted. Alternatively, the image or video may be provided to the primary controller in a first compressed format, where it is decompressed and re-compressed into a format that is amenable to the codec residing in the display modules. As shown in Figure 3, the image or video data may be transmitted in broadcast or multicast schemes in which a single compressed file or data stream is provided by the primary controller 30 to each module 20, with each module receiving identical copies of the file or data stream. The primary controller thus preferably comprises an interface for transmitting image data to the display modules, and optionally further comprises a processor and a codec for compressing the image data prior to transmission. While multicasting refers to sending data simultaneously to a set of nodes across a network, broadcasting refers to sending data to all nodes on the network. Because all display modules receive all of the data for the entire assembly of modules, part of the decompressed image or video will be unused for display on any given module. Therefore, this data can be deleted if desired. While this data transmission and decompression scheme may seem highly redundant (each module in the system must decompress an identical file), the usefulness of the scheme lies in the fact that dividing a file into pieces intended solely for individual modules will adversely affect the data compression ratio and/or fidelity.

This one-to-many transmission format is supported by a number of transmission standards, including ZigBee, WiFi, Ultra Wide Band, MiWi, Bluetooth, 3G, 4G, or other protocols based on the 802.11 , or 802.15 standards. In a multicast scheme, the primary controller sends a file or data stream simultaneously to a number of nodes, where the nodes are display modules. The aim of multicasting is to reduce congestion on a network by speaking to all the required nodes at once. The drawback of this type of communication is that it can be prone to errors because the nodes do not communicate a receipt of packet acknowledgement in order to conserve bandwidth. By contrast, this type of acknowledgement is generally done with typical IP unicasting. Error checking methods such as those included in the Pragmatic General Multicast (PGM) protocol can be used to minimize errors. A data checksum may be used by each module during broadcast or multicast in order to detect any loss of data integrity. Upon detection of an error, a module may notify the primary controller may rebroadcast, multicast, or unicast the lost or corrupted data to the module or modules that have detected errors. In this embodiment in which image or video data is broadcasted or multicasted by the primary controller, each display module decodes or decompresses the file or data stream with the codec provided in the control system, processes the decoded data and delivers the appropriate spatial subset of the image data to the one or more display controllers. This embodiment is particularly suited to many standard compression codecs, such as MPEG-2 and H.264.

In another embodiment, an image or video file is spatially subdivided by a processor residing in the primary controller prior to transmission, as shown in Figure 4 The primary controller could then transmit module-specific individual files, shown schematically as 40, or data streams using the known address of each module. However, sending the entire file at once to all of the modules in its compressed form is likely preferable because media files, once compressed using conventional methods, are difficult to separate into spatial components and retain a large compression ratio. Moreover, image and video files that are compressed using traditional compression algorithms such as JPEG or MPEG are only useful once they are decoded; in their compressed state, the images are locked in a state in which nothing can be extracted or scaled. Due to the processing power and inexpensive nature of processors, redundant decompression of the entire image by the module control system and selection of the spatially relevant portion is a preferred option.

While the above embodiments provide solutions for the delivery of compressed image and video content to modular display systems, it is important to consider evolving applications such as the emerging need to delivery live high definition video to large displays. As discussed above, compression enables the delivery of high-quality images and videos to modular displays without placing exorbitant demands on bandwidth. Unfortunately, real-time, high quality HD MPEG encoding with very low latency is often limited high-end rack mounted systems due to the processing requirements to deliver rapid encoding and decoding.

This problem may be circumvented according to the following embodiment, which enables the delivery of rapid, high-quality decoding of HD encoded video. This embodiment incorporates a wavelet-based algorithm that generates compressed data that retains the ability to easily extract different representations of the image for various end applications without the need to recompress the data. Unlike the aforementioned modular display system embodiments that employ conventional compression codecs such as MPEG, the present embodiment provides a wavelet-based compression codec in which image or video data can be spatially subdivided into address-specific files containing only the necessary spatial data for a particular display module while retaining full compression.

An exemplary form of such a wavelet-based codec is the JPEG2000 codec, which supports both lossless and lossy compression.

JPEG2000 employs wavelets to separates a signal into different frequency bands, and supports the analysis of each frequency band depending on the resolution or the scale [1]. JPEG2000 encoding functions by sending an image to a set of wavelet filters, where it is transformed into wavelet coefficients. These coefficients correspond to the entire image, in contrast to the method of using discrete compression blocks as in JPEG or MPEG. Wavelet coefficients are then grouped into subbands, which describe specific horizontal and vertical spatial frequency ranges of the entire image. These subbands are further resolved into spatial areas known as precincts, which are rectangular areas of the image in which the wavelet coefficients form approximate spatial blocks.

Precincts are then segmented into equal-sized code blocks, which are then entropy coded using an algorithm that provides a stream of compressed data that progressively improves the accuracy of the decoded data. Each code block may be accessed independently and can be grouped according to its significance to the particular application.

Accordingly, in a preferred embodiment, the control subsystem within each display module includes a wavelet-based compression codec (such as JPEG2000) capable of spatial segmentation. In one embodiment, the primary controller includes a corresponding codec for encoding image or video data, while in another embodiment the image or video data is provided to the primary controller in a pre-encoded format. Alternatively, the image or video may be provided to the primary controller in a first compressed format, where it is decompressed and re-compressed into a wavelet-based codec capable of spatial segmentation.

In this embodiment, the primary controller advantageously spatially segments the compressed image or video data prior to transmitting the data to the display modules. The spatial segmenting results in a plurality of individual compressed files or data streams, which correspond to specific spatial areas of the full image or video. Using predefined calibration or lookup tables, the primary controller maps each file or data stream to an address of a display module. The individual files or data streams are then transmitted to the appropriate display modules. Each display module therefore receives a unique file which can be decompressed using the wavelet-based codec residing in the module's control subsystem.

In a further embodiment, the modular display system according to the preceding embodiment further enables the primary controller to process data that is initially compressed with a wavelet-based compression code, where the processing enables the primary controller to selectively modify the resolution, image quality, bit rate, and YCbCr component sampling for optimal transmission.

In another embodiment, the modular display system further serves as a wireless access point for internet connectivity. For example, the primary controller of the system may include a WiFi wireless router. Preferably, access to the wireless network requires authorization. More preferably, the authorization includes information that can only be ascertained by reading the information displayed on the modular display system. For example, the authorization may be a password that is a brand name displayed in an advertisement on the modular display. In this manner, the authorization step requires that users of the wireless access point read information on the display. Preferably, a user would only be granted access for a fixed period of time. When the time period is exceeded, the user would be required to view the display again and follow an authorization step. Additionally, the bandwidth per user may be limited, and the total data downloaded or uploaded over a selected time period may be constrained.

As used herein, the terms, "comprises" and "comprising" are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in this specification including claims, the terms, "comprises" and "comprising" and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.

The foregoing description of the preferred embodiments of the invention has been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiment illustrated. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims and their equivalents. REFERENCES

1. Graps. A, "An Introduction to Wavelets," IEEE Computational Science and Engineering, Summer 1995, Volume 2, Number 2

2. Bako, C₁ "JPEG2000 Compression", Analog Dialogue 38-09, September 2004.

Claims

THEREFORE WHAT IS CLAIMED IS:

1. A display module for use in a modular display system, comprising: a display subsystem comprising an array of display elements; a control system comprising an interface for receiving compressed image data, a processor and a codec for decompressing said compressed image data, and a display driver for driving said display elements to display said decompressed image data; and an external connection means for providing electrical power to said display module.

2. The display module according to claim 1 wherein said control system further comprises a unique address for identifying a relative spatial location of said display module in a modular display system.

3. The display module according to any one of claims 1 and 2 wherein said interface for receiving compressed image data is selected from the group consisting of a wireless receiver, a wireless transceiver, and a data port.

4. The display module according to any one of claims 1 to 3 wherein said interface for receiving compressed image data is selected from the group consisting of a power-line receiver, a power-line modem, and power-line transceiver.

5. The display module according any one of claims 1 to 4 wherein said codec resides in software.

6. The display module according to any one of claims 1 to 5 wherein said codec is provided in hardware.

7. The display module according to any one of claims 1 to 6 wherein said codec comprises a wavelet-based codec.

8. The display module according to any one of claims 1 to 7 further comprising a weatherproofed housing.

9. A modular display system for displaying image data, comprising: a plurality of display modules, wherein each display module comprises: a display subsystem comprising an array of display elements; a control system comprising an interface for receiving compressed image data, a processor and a codec for decompressing said compressed image data, and a display driver for driving said display elements to display said decompressed image data; and an external connection means for providing electrical power to said display module; and means for mounting said display modules in a desired spatial arrangement; and a primary controller comprising an interface for transmitting said compressed image data to said plurality of display modules.

10. The system according to claim 9 wherein said plurality of display modules are arranged to display one of a single composite image and a single composite video.

11. The system according to any one of claims 9 and 10 wherein a control system of a given display module further comprises a unique address for identifying a relative spatial location of said given display module in said modular display system.

12. The display system according to any one of claims 9 to 11 wherein said interface for receiving compressed image data comprises one of a wireless receiver and a wireless transceiver, and wherein said interface for transmitting said compressed image data comprises one of a wireless receiver and a wireless transceiver.

13. The display system according to any one of claims 9 to 11 wherein said interface for receiving compressed image data is selected from the group consisting of a power-line receiver, power-line modem and power- line transceiver and said interface for transmitting said compressed image data is selected from the group consisting of a power-line transmitter, power-line modem and power-line transceiver.

14. The display system according to any one of claims 9 to 13 wherein said codec resides in software.

15. The display system according to any one of claims 9 to 14 wherein said codec is provided in hardware.

16. The display system according to any one of claims 9 to 15 wherein said codec is a wavelet-based codec.

17. The display system according to any one of claims 9 to 17 wherein said primary controller further comprises a processor and a codec for compressing image data prior to transmitting said image data to said display modules.

18. The display system according to claim 11 wherein said primary controller transmits said compressed data in a multicast format to said display modules.

19. The display system according to claim 11 wherein said primary controller further comprises a processor programmed to spatially segment said image data, correlate said spatially segmented image data with said unique addresses of said display modules, compress said spatially segmented image data, and transmit said spatially segmented and compressed image data to said display modules according to said unique addresses.

20. The display system according to any one of claims 9 to 19 wherein said primary controller further comprises a wireless router providing wireless access to one or more users.

21. A method for displaying image data on a display module within a modular display system, said display module comprising: a display subsystem comprising an array of display elements; a control system comprising an interface for receiving compressed image data, a processor and a codec for decompressing said compressed image data, and a display driver for driving said display elements to display said decompressed image data; and an external connection means for providing electrical power to said display module; said method comprising the steps of: receiving compressed image data transmitted by a primary controller; processing said compressed image data with said processor and codec to obtain decompressed image data; and providing said decompressed image data to said display driver for driving said display subsystem to display said decompressed image data.

22. The method according to claim 21 wherein said compressed image data is transmitted and received wirelessly.

23. The method according to any one of claims 21 and 22 wherein said display module further comprises a unique address for identifying a relative spatial location of said display module in said modular display system.

24. The method according to any one of claims 21 to 23 wherein said compressed image data is broadcasted to a plurality of display modules by said primary controller, and wherein said processor further processes said decompressed image data to obtain a spatial subset of said decompressed image data for display on said display subsystem according to said unique address.

25. The method according to claim 24 wherein said processor deletes decompressed image data relating to other addresses prior to providing said decompressed image data to said display driver.

26. The method according to any one of claims 21 to 23 wherein said compressed image data pertains to a spatial subset of said image data, wherein said spatial subset corresponds to a spatial location and size of said display module, and wherein said primary controller transmits said compressed image data to said display module according to said unique address.

27. The method according to claim 26 wherein said primary controller further comprises spatial calibration data associating said unique address with a spatial location of said display module.

28. The method according to claim 27 wherein said primary controller further comprises a processor and a codec for spatially segmenting said image data based on said spatial calibration data and compressing said spatially segmented image data.

29. The method according to any one of claims 21 to 28 wherein said primary controller further comprises a processor for modifying a property of said image prior to compressing and transmitting said image data, wherein said property is selected from the group consisting of resolution, image quality, bit rate, and YCbCr component sampling.