SCALABLE VIDEO CODING

FIELD OF TOE DISCLOSURE

The present disclosure generally relates to a Network Personal Video Recorder

(NPVR) system. More particularly, and not by way of my limitation, the present disclosure is directed to an NPVR system and a method on an NPVR system for storage o f program assets. BACKGROUND

Network-based PVR systems are well known as a means of allowing users to record broadcast programming content in network-based PVRs in a manner similar to the ability to record the same broadcast content in noiv-netvvork-based equivalents such, as digital video recorders (DVRs) and regular personal video recorders (PVRs). In general an NPVR device allows a user or subscriber to record broadcast programs of interest for subsequent viewing, and may provide various recording options, such as recording every episode of a designated program over a. period of time, such as a TV program season. The NPVR device may also record broadcast programming content in response to the user tuning to a channel and selecting the record function. The presentation of the recorded programming content can be manipulated, e.g., by exercising rewind; pause and last-forward -functions.

A concern for providers of an NPVR system is to effectively manage the storage of recorded content. Under current law, an NPVR system is required to store a unique copy of a recorded program for each subscriber that records the program. When the content is high definition (FID), the requirement to store a separate copy for each subscriber become very expensive and is expected to become prohibitively expensive with emerging technologies such as 4K video, also known as ultra-high definition.

SUMMARY

The present patent disclosure is broadly directed to a network personal video recorder (NPVR) system and method. In a method embodiment operating at an NPVR element, the method includes receiving a request from a user to record a program asset on a channel . When a count of enhancement recordings of t he channel is equal to zero, i.e., no other users are currently recording on this channel, the method begins capturing a plurality of enhancement layer encodes from the broadcast feed of the channel into an enhancement warehouse. Additionally, capture of a base layer encode of the broadcast feed of the channel is started, with the captured video being stored in an NPVR warehouse that is associated with the user; the count of enhancement recordings of the channel is then incremented by one.

in another aspect, an embodiment of a network element or node operable in an. NPVR system is disclosed. The NPVR element comprises a recording controller, whic is adapted to receive a request front a user to record a program asset provided on a channel, and a recorder, controlled b the recording controller and adapted to record an encoded ba.se layer of the program asset in an NPVR warehouse associated with the user. The network element is als adapted, when a count of enhancement recordings of the channel is equal to zero, to record a plurality of encoded enhancement layers in an enhancement warehouse and is further adapted to increment die count of enhancement recordi ngs of the channel by one.

in a still further aspect, an embodiment of non-transitory computer-readable medium containing instructions stored thereon is disclosed. When the stored. instructions are executed by a computer system configured, to operate as an NPVR element, the computer system is operable to perform an embodiment of the method set forth above. Further features of the various embodiments are as claimed in the dependent claims.

As will be explained in further detail hereinbeknv, one or more of the embodiments of the present disclosure aim to address at least some of the concerns set forth in the foregoing background section, inter alia.. For instance, one or more embodiments of the present disclosure may beneficially reduce network-based storage required in conventional NPVR. implementations. Various additional benefits and advantages will be apparent in view of the following description and accompanying Figures. BRIEF l7ESC.RiPTl.ON OF THE DRAWINGS

Embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the Figures of the accompanying drawings in which like references indicate similar elements. It should be noted that different references to "an" or "one'' embodiment in this disclosure are not necessarily to the same embodiment, and such references may mean at least one. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection, with other embodiments whether or not explicitly described.

The accompanying drawings are incorporated into and form a part of the specification to illustrate one or more exemplary embodiments of the present, disclosure. Various advantages and features of the disclosure will be understood from the following Detailed Description taken in. connection with the appended claims and with reference to the attached drawing Figures in which:

FIG. 1 depicts a network environment that Includes a network personal video recorder (NFVR) system according to an embodiment of the present patent application.;

FIG. I A. depicts a block diagram showing the flow of information between elements of an NPVR. system during recording of a program asset according to an. embodiment of the present patent application;

FIG. 2 depicts a block diagram show ing an embodiment of the flow of information between elements of a NPVR system during playback of a program, asset according to an embodiment of the present patent disclosure:

FIG. 3 depicts a block diagram show ing an embodiment of the flow of information between elements of a NFVR system during play back of a program asset according to an embodiment of the present patent disclosure;

FIG. 4 A depicts a flowchart of a method of processing a request to record at an NPVR node according to an embodiment of the present patent disclosure;

FIG. 4B depicts a flowchart of a method of processing a request to stop recording at an NPVR node according to an embodiment of the present patent disclosure; FIG. 5 A depicts a flowchart of a method of processing a request to playback a recording at an NPVR node according to art embodiment of the present -patent disclosure; and

FIG.5B depicts a flowchart of a method of processing a request to playback a recording at an NPVR node according to an embodiment of the present patent disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following descript ion, numerous specific details are set forth with respect to one or more embodiments of the present patent disclosure. .However, it should be understood that one or more embodiments may be practiced without such specific details. In other instances, well-known subsystems, components, structures and techniques have not been shown in deiaii in order not to obscure the understanding of the example embodiments. Accordingly, it will be appreciated by one skilled in the art that the embodiments of the present disclosure may be practiced, without such specific details, it should be further recognized that those of ordinary skill in the art, with the aid of the Detailed Description set forth herein and taking reference to the accompanying drawings, will be able to make and use one or more embodiments without undue experimentation.

Additionally, terms such as "coupled" and "connected," along with their derivatives, may be used in the following description, claims, or both. It. should be understood that tlie.se terms are not necessarily intended as synonyms for each other, "Coupled" may be used to indicate that two or more elements, which may or way not be in direct physical or electrical contact with each other, co-operate or interact with each other, "Connected'* may be used to indicate the establishment of communication, i.e., a communicative relationship, between two or more elements that are coupled with each other. Further, in one or more example embodiments se forth herein, generally speaking, an element, component or module ma be configured to perform a function if the element is capable of performing or otherwise structurally arranged to perform that function.

As used herein, a network element or node may be comprised of one or more pieces of service network equipment, including hardware and software that communicatively interconnects other equipment on network (e.g., other network elements, end stations, etc.), and Is adapted to host one or more applications or services with respect to a plurality of subscribers. Some network elements may comprise "multiple services network elements" that provide support for multiple networking functions, in addition to providing support for multiple application services. Subscriber end stations (e.g., set-top boxes, workstations, laptops, nefbooks, palm tops, mobile phones, sroartphones, multimedia phones, portable media players, etc.) may access or consume content services provided over broadcast networks (e.g., cable networks) as well as a packet-switched wide area public network such as the Internet via suitable service provider access networks.

One or more embodiments of the present patent disclosure- may be implemented using different combinations of software, firmware, and/or hardware. Thus, one or mom of the techniques shown in the Figures (e.g., flowcharts) may be implemented using code and data stored and executed on one or more electronic devices or nodes (e.g., a network ^' element, a subscriber device or end station, etc.). Such electronic devices may store and communicate (interiialiy and/or with other eiecironic devices over a network) code and data using computer-readable media, such as non-transitory computer-readable storage media (e.g., magnetic disks, optica! disks, random, access memory, read-only memory, flash memory devices, phase-change memory, etc.), transitory computer-readable transmission media (e.g., electrical, optical, acoustical or other form of propagated signals - such as carrier waves, infrared signals, digital signals), etc. in. addition, such electronic devices may ty pically include a set of one or more processors coupled to one or more other components, such as one or more storage devices (non-transitory machine-readable storage media), user input/output devices (e.g., a keyboard, a touch screen, a pointing device, and/or a display), and network connections. Thus, the storage device or component of a given electronic device may be configured to store code and/or data for exec ution on one or more processors of that eiecironic device for purposes of implementing one or more techniques of the present disclosure.

Referring now to the drawings and more particularly to FIG. 1 , depicted therein is an example network environment that, includes an embodiment of as NFVR system 100 of the present patent application for providing recording and playback capabilities with, respect to any known or heretofore unknown broadcast digital, assets or program assets for a. number of subscribers. Network element 101 provides recording and playback capabilities to subscribers of network 124 via set-top boxe 126, 128, 1.30, 1.32 at the subscriber's premises in. accordance with an. embodiment of the present disclosure. In the disclosed example, network 124 is a broadband broadcast network, such as an internet Protocol television (l ^' PTV) provider or Hybrid Fibre-Coaxial (HFC) cable provider, although embodiments of the disclosure are not .limited by these types of providers. Further, set-top boxes 126, 128, 130, 1 32 may comprise appliances that not only connect the broadband, broadcast network, t a television or other display device for receiving program assets for live viewing and/or playback, but also operate as command console thai can accept user inputs, commands or requests to interact with an network element disposed in the NPV ^' R system 100 (e.g., NPVR element 101 ). Example set-top boxes may include PCs, laptops, notebook computers, tablets, discrete set top boxes (STBs), virtual STBs, integrated TV /STBs, smattphones, smart TVs, and the like. Program assets are stored by network, element 1.01 using multilayer video technology known as Scalable Video Coding (SVC). SVC has so far been set forth in the following standards: H262/MFEG-2 (published as part of iSO/lEC 13818-2), R254/ PEG-4 (published as part of ISO/lEC 14496) and in H.265/MEVC (published as part of ISO/1.EC 23008-2), The disclosed embodiments are also applicable to any heretofore unknown standards that ma be developed, as long as the video is stored as scalable layers. According to Scalable Video Coding, content is encoded as a base layer and one or more enhancement lavers in order to meet the needs of users havina wide variations in terms of connection qualities and end devices. The base layer contains a lower bit-rate video and the audio stream. The base layer is the only layer that can be decoded into playable video; each of the enhancement layers provides "enhancement ^" * information that can be used to reconstruct a higher level of video when used with the base layer, but which cannot be played on its own. SVC uses high compression coding that allows the enhancement layers to provide temporal scalability (i.e., frame rate), spatial scalability (i.e., picture size), SNR scalability (i.e., quality and fidelity) or a hybrid or combination of these seaiabilities. With large amounts of information coded in the various enhancement layers, the base layer requires a much smaller space for storage than do the various enhancement layers associated with the base layer. When network element 101 records program asset for a user, a copy of the base layer is stored in the user's reserved storage space in the subscriber's NPVR warehouse 1 13, while the associated enhancement layers are stored in enhancement layers warehouse 107. As will be seen in greater detail below, when multiple users record a program asset, each subscriber has a copy of the base layer stored in their individual NPVR storage in warehouse 1 13, but only a single copy of each, enhancement layer needs to be stored in enhancement layers warehouse 107, providing savings in the amount of storage space that is needed for the recorded content.

As seen in FIG, I , network, element 1.01 contains a base and enhancement layers eneoder/transeoder 104, which receives incoming broadcast content and provides output feeds that are coded as a base layer and multiple enhancement layers, with each enhancement layer encoded for a specific size and fidelity of display. A base and enhancement recorder 106 records the base layer into subscriber's NPVR warehouse 11 3 and records the enhancement layers int enhancement layers warehouse J.07, NPVR base layer and enhancement layer stream pump 109 delivers content to the subscribers in response to playback requests. NPVR recording control 122 receives user requests and controls the recording process in response these requests, while and PVR. playback control 1 ί 1 receives user playback requests and controls play back of the recorded programs. Content feed source 103 provides program assets to NPV . element 1 1. The program assets provided by content feed, source 103 can include any type of broadcast audio/video content or program segment having a start time and an end time such as live and/o recorded over-the-ak free network television (TV) shows or programs, pay TV broadcast programs via cable networks and IPTV programs as well as other content assets provided by content owners or providers.

With reference now t FIG. 1 A, the flow of information shown in FIG, 1 A. is discussed according to an embodiment of the disclosure. I this example, four user set- top boxes 126, 128, 130, 132 are shown, although it will be understood that the number of subscribers recording any given program asset can vary from none to a large number. Additionally, in at least some embodiments, a single user can record assets from multiple channels at the same time. Such complexities are not specifically shown for ease of understanding the present disclosure. Each of the subscribers provides instructions to node 1 ! using their respective set-top box 126, 128, 130. 132. The instructions can be contained in a pre-set recording request, e.g., record the program asset on channel Z between the times xx:xx:xx and xx:xx.:xx. Instructions can also be provided by manipulation of "record" and "stop" mechanisms that the subscriber activates to initiate or sto recording. These instructions are carried by network 124 to NPVR recording control 122. A the indicated start time or else when the user initiates recording, NPV.R. recording control 122 sends a. message to recorder 1 6 to initiate recording of appropriate base and enhancement layers as requested by the subscriber. Broadcast program assets are received on a number of channels from conten feed source 103. One such channel is shown as Channel Z feed 102. One skilled in the art will appreciate that multiple channels can be received and recorded from content feed source 103 at one time, although only one channel is represented in the figure for simplicity. The broadcast received via Channel Z feed 102 in an example embodiment is sent with a resolution of 1920x1.08Qp at .15 Mbs. In this example, base and enhancement encoder/transcoder 1.04 outputs base layer stream 140 and three enhancement layer streams 142, 144, 146, although the number of enhancement layer streams can be greater or fewer. Base layer stream .140 has a resolution of 416x234 at 500 Kbs. Enhancement layer stream 14.2 is a hybrid enhancement layer with a resolution of ?20x480p at 2 Mbs. Similarly, enhancement layer stream 1 4 is a hybrid layer with a resolution of 1 280x720» and enhancement layer 146 is a hybrid layer with a resolution of 1920x1080i/p. Recorder 106 receives base layer stream 140 and enhancement layer streams 142, 1 4, 1 6 and stores a copy of base layer stream 140 in subscriber NPV.R warehouse 1 13 for each subscriber who is current.lv recordms. As long as any subscribers are recording Channel Z, recorder 106 will also store a copy of each of enhancement layer streams 1 2, 144, 146 in enhancement layers warehouse 1.07. As illustrated, enhancement layer stream 1 2 is stored in enhancement layers warehouse 10? as Enhancement Layer 3 1 12, Similarly, enhancement layer stream 144 is stored as Enhancement Layer 2 1 1.0 and enhancement layer stream 146 is stored as Enhancement Layer 1 1.08. Enhancement Layers 108, 1 10, 1 1.2 each contain their respective enhancement layer capture for a. specific segment of time, e.g., a one hour segment.

The enhancement files, which are to be shared by multiple users, are stored during any time period in which any user is recording on Channel Z, in contrast, the base layer file stored in each subscriber's NPV'R storage is only recorded for the period requested. For example. User A requests that Channel Z be recorded during the time frame 9:00 AM to 9:30 AM. Accordingly, at the end of the specified time period. User A base 1 14 contains a base layer recording at resolution 416x234p at 500 Kbs covering the time frame from 09:00:00 to 09:30:00. User B requests that Channel Z be recorded during the time period 9:20 AM to 9:30 AM; consequently User B base 1 16 contains a base layer recording at .resolution. 416x234p at 500 Kbs covering the lime frame .from 09:20:00 to 09:30:00. User C requests that Channel Z be recorded during the time frame 9:00 AM to 9:45 AM; consequently User C base 1.1.8 contains a base layer recording at resolution 416x234p at 500 Kbs covering the time frame from 09:00:00 to 09:45:00. User N selects the record button on Channel Z at 9:09 AM and at 1 :00 AM has not yet selected the stop button. User N Base 120 contains a base layer recording at resolution 41 όχ234ρ at 500 Kbs covering the time .frame from 09:08:00 to ??:??:??,. with. ?? denoting a time the user will hit the stop button.

Turning next to FIG. 2, shown is the information flow for playback of a recorded program asset according to an embodiment of the disclosure. In the disclosed embodiment. User A STB 126 contains decoder 220, which is able to receive the base and enhancement layers and decode 2the separate files into an appropriately enhanced playable video format. User A STB 1.26 sends a request for playback at standard definition (SD) of the program asset that was recorded in FIG _* l.A, which in the example embodiment is recording of Channel Z during the time period 09:00 through 09:30 AM. The request is sent through netw ork 1.24 and received at playback control 210. Playback control 210 then informs PVR base layer & enhancement layer stream pump 109 to provide the requested playback of Channel 2 for User A from 09:00:00 to 09 30:00. Once received at NPVR Stream. Pump 109, base and. enhancement processor 202 identifies and retrieves the requested User A base 1 14 and further determines the presentation time stamps (PI ^' S) that correspond to the beginning and. ending times for the recorded base layer. In this example, the recording starting time of 09:00:00 AM is equivalent to a PTS of 330000000 and the recording stopping time of 09:30:00 is equivalent to a PTS of 492000000. Base and enhancement processor 202 then retrieves the appropriate enhancement layer, e.g. enhancement layer 3 1 12, which when combined with User A base 1 14 will provide SD video to the user. Base and enhancement processor 202 then parses enhancement layer 1 12 to locate starting PTS 330000000. Once the starting PTS is located, enhancement layer J 12 and User A. base 1 14 are streamed to MPEG transport stream (TS) multiplexor (MUX) 206 as enhancement stream 230 and base stream 232, MPEG TS MU 206 outputs a multiplexed transport stream 240 (shown as dotted lines). In the illustrated embodiment, transport stream 240 contains three elementary streams, i.e., enhancement layer stream 234, base layer stream 236 and audio stream 238. Transport stream 240 is provided to streamer 208, which streams the multiplexed transport stream, to user A STB 326 via network 1 4. At STB 126, decoder 220 decodes/tratiscodes the transport stream into a format that can be forwarded to the user's television or other display device. In an alternate embodiment that is not specifically shown, each of the elementary streams 234, 236, 238 shown in FIG. 2 is sent as & separate transport stream to streamer 208, which in turn streams the three transport streams to user A S IB 126.

FIG. 3 illustrates another embodiment of MPV base layer and enhancement layer stream pump 109 that can be used with a user set-top box that does not contain a decoder for scalable video coding. As in the example discussed in FIG, 2, User A STB 126 sends a request for playback of the program asset recorded in FIG. I A, this time requesting a high-definition (HI. ⁾ ) version of the video. The request is sent via network 1.24 to playback control 210, which sends a message to base layer and enhancement layer stream pump 109. Base and enhancement processor 202 retrieves User A base 1 14 and MD enhancement layer 108. Processor 202 determines the starting PTS to be 330000000 and the ending PTS to be 492000000 for User A base 1 14 and locates starting PTS 330000000 of enhancement layer 108. Enhancement layer 108 and User A base 1 14 are then sent to transcoder 304, where these two layers are trans-coded to a standard format, e.g. H264/MPEG-4, and sent to MPEG TS MUX 206 as video stream 330 and audio stream 332. At MPEG TS MUX 206, video stream 330 and audio stream 332 are multiplexed to form a transport stream containing two elementary streams, video stream 334 and audio stream 338. This combined transport stream, is sent to streamer 208, which streams the transport stream through network 124 to User A STB 126 for display on the user's displa device.

FIG. 4A illustrates the process (400A) of initiating capture of a program asset according to an embodiment of the disclosure. NPVR element 101 receives (405) a -Π- user-initiated "Record" signal or else the starting time is reached for a request to record a program on Channel Z between times X.X:XX:XX and XX:X.X:XX, NPVR element 101 compares (410) the number of enhanced session recordings currently being captured for channel Z, designated herein as FR(Z), if ER(Z) is currently equal (4.15) to zero, i.e., no other users arc currently recording a program on channel Z. NPVR element 101 starts (420) the enhancement layer encode capture for channel. Z in. enhancement layers warehouse 107; otherwise, if E. (Z) does not equal zero, the enhancement layer encode capture is alread being done and does not need to be started. NPVR element 101 starts (425) a base layer encode capture of channel Z in. User X ^' S NPVR storage in subscriber's NPVR warehouse 1 13 and also increments (430) ER(Z) to indicate that an additional recording is now being made of channel Z, After being started, capture of the base layer in subscriber warehouse 1 13 and capture of the enhancement layers in warehouse 107 continues until the recording session is stopped, as illustrated in FIG. 4.B.

FIG. 4.B illustrates the process (400 ^' B) of stopping the capture of a program asset according to an embodiment of the disclosure. NPVR element 1.01 receives (455) a user-initiated "Stop" or else reaches the end time XX:XX;XX designated in the user's request to record channel Z. When this occurs, NPVR element 101 determines whether ER(Z) is equal (460) to one. I ER(Z) is equal to one, indicating that the current user is the only subscriber currently recording channel Z, NPVR element 101 stops (465) the enhancement layer encode capture of channel 2; if ER(Z) is not equal to 1 , then other subscribers are recording channel 2 and the enhancement layer encode capture will continue. NPV element 101 stops (470) base layer encode capture in User X's NPVR. storage for channel Z and decrements ER(Z) to indicate that there is one less subscriber currently recording channel. Z.

FIG. 5A illustrates the process (500A) of playback of a program asset according to the embodiment of the disclosure shown in. FIG. 2, NPVR element 101 receives (505) a user request to play recording Y for channel Z, which has a starting media time of 9:00 AM and an ending media, time of 9:30 AM. Element 101 will retrieve {510) the base layer encode capture, e.g. 1 14, lor recording Y from subscriber warehouse 1 13 and use the recorded times to generate (515) a starting PI ^' S value and an ending PTS value from the base layer encode capture. After retrieving (520) the appropriate enhancement layer encode capture t le from enhancement layer warehouse 307, e.g. enhancement layer 1 1 , the enhancement layer encode capture file is parsed (525) searching for the PIS thai corresponds to the base layer starting PTS. Once the startin PIS has been located, element 101 feeds (530) the base layer encoding, e.g. 1.1 , and the enhancement layer encoding, e.g., 1 2. at the starting PTS into a real-time MUX, such as MPEG TS MUX 206, Element 101 then streams (535) the output from the real-time MUX to the user's SIB, which contains an SVC decoder (220) that can decode the stream into a standard format playable on the user's television or other display screen.

FIG. 5B illustrates the process (500.B) of playback of a program asset according to the embodiment of the disclosure shown in FIG. 3. In the method disclosed in this figure, NPVR. element 101 receives (555) a. user request to play recording Y for channel Z, which again has a starting media time of 9:00 AM and an ending media time of 9:30 AM. NPVR element 101 will retrieve (560) the base layer encode capture, e.g., 1 14, for recording Y from subscriber warehouse 1 13 and use the recorded times to generate (565) a starting PTS value arid an ending PTS value from the base layer encode capture. After retrieving (570) the appropriate enhancement layer encode capture file, e.g., 108, from enhancement layer warehouse 107, the enhancement layer encode capture file is parsed (575) searching for the P I ^' S that corresponds to the base layer starting PTS. Once the starting PTS has been located, element 10! transcodes (580) the base layer encoding and the enhancement layer encoding at the starting PTS into a standard video format stream, e.g., MPfiG-4. NPVR element 5.01 then feeds (585) the transcoded stream into a real-time multiplexor, e.g., MUX 206, and then sends the multiplexed stream t streamer 208. Streamer 208 streams (590) the output stream to the users STB, which in torn provides the program asset to the user ^' s television or other display,

it should he appreciated that the embodiments of the present disclosure can. advantageously reduce the amount of network-based storage required in conventional .NPVR. implementations where copies of all requested programs are typically stored at multiple resolutions for each, subscriber. Instead of storing the multiple large content files on the NPVR system for each subscriber, smaller base layers are stored for the individual users in order to meet legal requirements, while the larger enhancement layer flies, which are not playable video, are not reproduced for each subscriber,, but shared by multiple subscribers.

Although the embodiments shown above save only a single copy of the enhancement layers, a number of modifications to this method are possible, in one embodiment, when a second user requests a recording of an channel, e.g., channel Z, which is already being recorded, a subset of the fid! set of enhancement layers can be stored. For example, rather than proh ibiting the making of an addi tional copies of the enhancement layers, as disclosed in the flowcharts, at least one of the enhancement layers can. be stored when additional subscribers are recording the channel. In a further variation, the entire set of the enhancement layers may be stored in addition to the base layer responsive to a recording request by the second or subsequent users requesting the same content on a channel.

In the foregoing Detailed Description, functionalities of the various elements including components blocks labeled or described as "module" or "process" or "processor" or "controller" or "computer" may be provided through the use of dedicated hard ware as well as hardware capable of executing stored, or preconflgured software. When provided by a processor, the functions ma be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared or distributed. Moreover, a "processor" or "controller" or "memory" may include, without limitation, digital signal processor (DSP) hardware, ASIC hardware, read only memory (ROM), random access memory (RAM), and/or other storage media.

Although various embodiments have been show and described in detail, the claims are not limited to any particular embodiment or example. None of the above Detailed Description should, be read, as implying that any particular component, element, step, act, or function is essential such that it must be included in the scope of the claims. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural, and. functional equivalents to the elements of the above-described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed b the present claims. Accordingly, those skilled in the art will recognize that the exemplary embodiments described herein -J - ean be practiced with various modifications and alterations within the spirit and scope of the claims appended below.