Apparatuses and methods for delivering data stream content to consumer devices

BACKGROUND

0001Aspects of this invention relate generally to delivery of content carried by data streams in broadband communication networks, and more particularly to apparatuses and methods that allow accelerated acquisition and rendering of data stream content by consumer devices in broadband communication networks.

0002Program providers such as multiple system operators (“MSOs”) deliver content (including but not limited to pre-recorded or live electronic signals representing: images; audio; software; services such as interactive television, Internet services, telecommunication services, video-on-demand services, and the like; and other data) from a variety of public and private sources to network devices in the homes of consumers (examples of consumer network devices include personal computers/systems, hard-drive storage devices, televisions, video camera recorders, video disk recorders/players, set-top boxes, telecommunication devices, video production devices, cable modems, and local gateways, among others) via wired and wireless broadband communication networks such as cable networks, satellite networks, and telecommunication networks.

0003MSOs are increasingly employing packet-data-based communication technologies such as the Ethernet and Internet Protocol (“IP”) to deliver content to consumers. MSOs generally encode content using one or more well-known technologies and distribute the encoded content to consumer network devices via multicast or unicast data streams, using central reception and transmission equipment configured for two-way interaction with the consumer network devices.

0004Video compression is one technology that enables the efficient distribution of content to consumers, and various industry protocols relating to video compression have been promulgated. Moving Picture Experts Group (“MPEG”) protocols (MPEG-2 and MPEG-4, for example) are video compression protocols generally implemented by encoder/decoder pairs (“CODECs”) that produce/decode an encoded data stream having a particular syntax, and the encoded data stream carries content to consumer devices over channels having limited bandwidth.

0005According to MPEG-2 and MPEG-4, each picture of an input video is partitioned into fixed-sized frames of data that are independently decodable. Intra-coded frames (“I-frames”)—frames that are coded without referring to other pictures within the input video—recur throughout a data stream and are used by CODECs to initially acquire and render encoded content, among other things. An MPEG Group of Pictures (“GOP”) represents the number of frames between recurring I-frames in an MPEG-compressed data stream. Other types of frames in an MPEG-compressed data stream include predictive-coded frames (“P-frames”), which predict forward in a GOP, and bidirectionally interpolated frames (“B-frames”), which predict both forward and backward in a GOP.

0006There is a tradeoff between the number of I-frames (indeed, any unit functioning as a recurring access point in any data stream) located in an MPEG-compressed data stream (hence, the time it takes to acquire and render the content carried thereby) and the bandwidth required to convey that compressed data stream (to broadcast it to CODECs associated with consumer network devices, for example). This tradeoff in an MPEG-compressed data stream may be illustrated by roughly computing an average number of bits per picture [b_ABE(N)] as follows: <maths id="MATH-US-00001" num="1"><math overflow="scroll"><mrow><mrow><msub><mi>b</mi><mi>AVE</mi></msub><mo>⁡</mo><mrow><mo>(</mo><mi>N</mi><mo>)</mo></mrow></mrow><mo>=</mo><mfrac><mrow><mrow><mo>(</mo><mrow><mrow><mo>(</mo><mrow><mi>N</mi><mo>-</mo><mn>1</mn></mrow><mo>)</mo></mrow><mo>+</mo><mi>X</mi></mrow><mo>)</mo></mrow><mo>⁢</mo><msub><mi>b</mi><mrow><mi>B</mi><mo>/</mo><mi>P</mi></mrow></msub></mrow><mi>N</mi></mfrac></mrow></math></maths>

0007where, <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0000"><ul id="ul0002" list-style="none"><li id="ul0002-0001" num="0008"> N=number of pictures per GOP </li><li id="ul0002-0002" num="0009"> X=ratio of bits per I-frame to bits per B- or P-frame </li><li id="ul0002-0003" num="0010"> b_B/P=number of bits per B-picture/P-picture </li></ul></li></ul>

0011A ratio [R] provides a comparison of the number of bits required for two different GOP lengths: <maths id="MATH-US-00002" num="2"><math overflow="scroll"><mrow><mi>R</mi><mo>=</mo><mfrac><mrow><mrow><mo>(</mo><mrow><mrow><mo>(</mo><mrow><msub><mi>N</mi><mn>1</mn></msub><mo>-</mo><mn>1</mn></mrow><mo>)</mo></mrow><mo>+</mo><mi>X</mi></mrow><mo>)</mo></mrow><mo>⁢</mo><msub><mi>N</mi><mn>2</mn></msub></mrow><mrow><mrow><mo>(</mo><mrow><mrow><mo>(</mo><mrow><msub><mi>N</mi><mn>2</mn></msub><mo>-</mo><mn>1</mn></mrow><mo>)</mo></mrow><mo>+</mo><mi>X</mi></mrow><mo>)</mo></mrow><mo>⁢</mo><msub><mi>N</mi><mn>1</mn></msub></mrow></mfrac></mrow></math></maths>

0012In one example, assuming X=3, a GOP length of N=6 requires 18% more bandwidth than a GOP length of N=15. Such additional bandwidth may be impractical or impossible to achieve in many broadband communication systems. Although protocols such as Real Time Streaming Protocol (“RTSP”) tightly synchronize client/server exchanges and may reduce the time required to acquire and/or render content, RTSP alone may not be practical for broadcast applications because of scalability issues.

0013There are therefore needs for bandwidth-conserving apparatuses and methods that allow accelerated acquisition and rendering of encoded content configured for broadcast distribution via packet data communication technologies to consumer devices within broadband communication networks.

SUMMARY

0014In accordance with one aspect of the present invention, a method for delivering content to a consumer network device such as a decoder is operable in a broadband communication network. The method includes: managing an original data stream, such as a Moving Pictures Experts Group (“MPEG”) data stream carrying the content, the original data stream having original recurring access units, such as intra-frame-compressed pictures, associated therewith, the original recurring access units usable by the consumer network device to acquire the content from the original data stream; replicating the original data stream to form a replicated data stream having replicated recurring access units, the replicated recurring access units usable by the consumer network device to acquire the content from the replicated data stream; offsetting the replicated data stream relative to the original data stream by a predetermined amount of time, the replicated recurring access units offset by the predetermined amount of time relative to the original recurring access units; and arranging for communication of the predetermined amount of time to the consumer network device. The predetermined amount of time is usable by the consumer network device to determine a next available recurring access unit from among a group consisting of at least one of the original recurring access units and at least one of the replicated recurring access units, and the next available recurring access unit is usable by the consumer network device to acquire the content.

0015The method may further include the steps of: at a first time, multicasting the original data stream to a first Internet Protocol (“IP”) address; and at a second time, which is delayed relative to the first time by the predetermined amount of time, multicasting the replicated data stream to a second IP address; and based on the next available recurring access unit, when determined, authorizing the consumer network device to join a multicast group at either the first or second IP address. When the next available recurring access unit is one of the original recurring access units, the step of authorizing includes authorizing the consumer network device to join a multicast group at the first IP address to acquire the content from the original data stream, and when the next available recurring access unit is one of the replicated recurring access units, the step of authorizing includes authorizing the consumer network device to join a multicast group at the second IP address to acquire the content from the replicated data stream.

0016The step of arranging for communication of the predetermined amount of time to the consumer network device may include the following steps: encapsulating a message including the predetermined amount of time within a transport layer data packet; and forwarding the transport layer data packet to the consumer network device according to a network layer protocol.

0017In accordance with another aspect of the present invention, a computer-readable medium is encoded with a computer program which, when loaded into a processor, implements the foregoing method.

0018In accordance with a further aspect of the present invention, a method for receiving content is operable in a broadband communication network. The content is carried via a first data stream having a first set of recurring access units and is also carried via a second data stream having a second set of recurring access units. The second data stream is a replica of the first data stream delayed by a predetermined amount of time and the second set of recurring access units is delayed relative to the first set of recurring access units by the predetermined amount of time. The method includes: arranging for receipt of a schedule via a first multicast IP address, where the schedule includes: a first time value, the first time value representing a past time at which an initial recurring access unit of the first set of recurring access units was broadcast, a second time value, the second time value representing a future time at which a subsequent recurring access unit of the first set of recurring access units will be broadcast, and the predetermined time; based on the schedule, determining a next available recurring access unit from among a group consisting of at least one recurring access unit from the first set of recurring access units and at least one access unit from the second set of recurring access units; when the next available recurring access unit is determined to be from the first set of recurring access units, selecting the first data stream from which to receive the content; and when the next available recurring access unit is determined to be from the second set of recurring access units, selecting the second data stream from which to receive the content.

0019The schedule may further include a reference time, such as a network time protocol time, at which the schedule was delivered, and the first time and the second time may be expressed relative to the reference time.

0020The step of selecting the first data stream may include joining a multicast group at a second multicast [P address, and sending an IGMP Join Group message. Likewise, the step of selecting the second data stream may include sending an IGMP Join Group message for a third multicast IP address. The step of arranging for receipt of the schedule may include receiving a content selection indication, such as a broadcast video channel selection or a video-on-demand channel selection, from a user of a consumer network device. The step of determining the next available recurring access unit may include consulting the schedule to determine the next available recurring access unit associated with the received content selection.

0021According to a still further aspect of the present invention, a computer-readable medium is encoded with a computer program which, when loaded into a processor, implements the foregoing method.

0022According to yet another aspect of the present invention, an apparatus for handling content configured for broadcasting to a consumer network device within a broadband communication network comprises: a network interface operative to handle a plurality of data packets; a computer-readable storage medium; and a processor (associated with the broadband communication network or the consumer network device) responsive to the computer-readable storage medium and to a computer program. When loaded into the processor, the computer program is operative to: arrange for access, via the network interface, to a first data stream carrying the content, the first data stream having a first set of recurring access units, the first set of recurring access units usable by a consumer network device to acquire the content from the first data stream; arrange for access, via the network interface, to a second data stream carrying the content, the second data stream having a second set of recurring access units, the second data stream a replica of the first data stream delayed by a predetermined amount of time, the second set of recurring access units delayed relative to the first set of recurring access units by the predetermined amount of time; arrange for access to a schedule, the schedule including: a first time value, the first time value representing a past time at which an initial recurring access unit of the first set of recurring access units was broadcast, a second time value, the second time value representing a future time at which a subsequent recurring access unit of the first set of recurring access units will be broadcast, and the predetermined time, a next available recurring access unit determinable, using the schedule, from among a group consisting of at least one recurring access unit from the first set of recurring access units and at least one access unit from the second set of recurring access units; when the next available recurring access unit is determined to be from the first set of recurring access units, arrange for receipt of the content from the first data stream; and when the next available recurring access unit is determined to be from the second set of recurring access units, arrange for receipt of the content from the second data stream.

0023According to a yet further aspect of the present invention, a method for delivering content to a consumer network device operable in a broadband communication network. The content is carried by a data stream having recurring access units associated therewith. The method includes: receiving notification of content selection activity, the content selection activity initiated by a consumer network device; based on the content selection activity, arranging for communication with a circular buffer, the circular buffer having at least part of the data stream inserted therein, the part of the data stream in the circular buffer having at least one recurring access unit associated therewith; based on the content selection activity, arranging for determination of a next available recurring access unit within the circular buffer; and arranging for delivery of a data packet including the next available recurring access unit to the consumer network device.

0024The step of arranging for determination of the next available recurring access unit may include determining a memory location of the next available recurring access unit in the circular buffer, and the step of arranging for delivery of the data packet may include arranging for delivery of the data packet using an internet multimedia control protocol such as Real Time Streaming Protocol.

0025According to a yet still further aspect of the present invention, a computer-readable medium is encoded with a computer program which, when loaded into a processor, implements the foregoing method.

0026According to an additional aspect of the present invention, an apparatus for handling content configured for delivery to a consumer network device within a broadband communication network, the content carried by a data stream having recurring access units associated therewith, includes: a network interface operative to handle a plurality of data packets; a computer-readable storage medium; and a processor responsive to the computer-readable storage medium and to a computer program. When loaded into the processor, the computer program is operative to: communicate with a circular buffer to receive at least part of the data stream inserted in the circular buffer, the part of the data stream in the circular buffer having at least one recurring access unit associated therewith; receive notification, via the network interface, of content selection activity initiated by a consumer network device; based on the content selection activity, arrange for determination of a next available recurring access unit within the circular buffer; and arrange for delivery, via the network interface, of a data packet including the next available recurring access unit to the consumer network device.

BRIEF DESCRIPTION OF THE DRAWINGS

0027<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram of a broadband communication network, in/with which various aspects of the present invention may be used.

0028<figref idref="DRAWINGS">FIG. 2</figref> is a block diagram of a generic network device having components that are included in the various network devices shown in <figref idref="DRAWINGS">FIG. 1</figref>

0029<figref idref="DRAWINGS">FIG. 3</figref> is a block diagram of an example of the consumer network device shown in <figref idref="DRAWINGS">FIG. 1</figref>, in/with which various aspects of the present invention may be used.

0030<figref idref="DRAWINGS">FIG. 4</figref> is a flowchart of a method, which is operable in a broadband communication network such as the network shown in <figref idref="DRAWINGS">FIG. 1</figref>, for delivering content to a consumer network device in accordance with certain aspects of the present invention.

0031<figref idref="DRAWINGS">FIG. 5</figref> is a flowchart of a method, which is operable in a broadband communication network such as the network shown in <figref idref="DRAWINGS">FIG. 1</figref>, for receiving content in accordance with further aspects of the present invention.

0032<figref idref="DRAWINGS">FIG. 6</figref> is a block diagram of an alternate operational embodiment of the stream processor shown in <figref idref="DRAWINGS">FIG. 1</figref>.

0033<figref idref="DRAWINGS">FIG. 7</figref> is a flowchart of a method for delivering content to a consumer network device in accordance with still further aspects of the present invention, which method is operable in a broadband communication network such as the network shown in <figref idref="DRAWINGS">FIG. 1</figref> that features the operational embodiment of the stream processor shown in <figref idref="DRAWINGS">FIG. 6</figref>.

DETAILED DESCRIPTION

0034Turning now to the drawings, where like numerals designate like components, <figref idref="DRAWINGS">FIG. 1</figref> is a block diagram of a broadband communication network <b>10</b>, in which various aspects of the present invention maybe used. As shown, network <b>10</b> is a cable network operated by a multiple system operator (“MSO”), but it will be understood that network <b>10</b> (and connections throughout) may be any public or private, wired or wireless, transmission infrastructure or technology, including but not limited to: a fiber-optic network; a coaxial cable network; a satellite network; a cellular network; a wireless network; the Internet; a television network; a radio network; a copper wire network; or any other existing or future transmission infrastructure or technology or combination thereof, operated by any type of program provider. Content <b>12</b> (which includes, but is not limited to, pre-recorded or live electronic signals representing: images; audio; software; services such as interactive television, Internet services, telecommunication services, video-on-demand services, and the like; and other data) is carried by one or more data streams, such as data stream <b>30</b>, and distributed via a network, such as hybrid fiber/coax (“HFC”) network <b>25</b>, to consumer network devices, such as consumer network device <b>14</b>.

0035As shown, consumer network device <b>14</b> is a cable or terrestrial set-top device, which has a stream acquisition client function <b>80</b> (discussed further below), although consumer network device <b>14</b> may be any wired or wireless device or combination of devices now known or later developed that is responsive to acquire and render content <b>12</b> in accordance with aspects of the present invention, including but not limited to a home- or office-based computer system, a gateway, a video receiving, recording or playback device, a stereo system, a television or monitor, a cable modem, a personal digital assistant, or a radiofrequency communication device.

0036In general operation of network <b>10</b>, a headend <b>22</b> facilitates distribution of content <b>12</b> to consumer network device <b>14</b>, and a Network Time Protocol (“NTP”) server <b>30</b> (discussed further below) is used to coordinate various activities and information between headend <b>22</b> and consumer network device <b>14</b>. Headend <b>22</b> includes a number of network devices or groups thereof—an Internet Protocol (“IP”) network <b>24</b> generating one or more content streams <b>50</b> (discussed further below); a stream processor <b>26</b> (having a stream acquisition agent function <b>70</b>, discussed further below) that generates broadcast streams <b>52</b> (discussed further below) and/or schedule <b>54</b> (also discussed further below) based on content stream(s) <b>50</b>; and a network of servers/routers <b>28</b> (having distribution agent functions <b>72</b>, also discussed further below) that receive broadcast streams <b>52</b> and/or schedule <b>54</b> for distribution to consumer network device <b>14</b> as one or more data streams <b>30</b>.

0037<figref idref="DRAWINGS">FIG. 2</figref> is a block diagram of a generic network device <b>200</b> that has functional components generally included in, or accessible by, network devices within system <b>10</b>, including elements of IP network <b>24</b>, stream processor <b>26</b>, servers/routers <b>28</b>, NTP server <b>30</b>, and consumer network device <b>14</b>. A processor <b>202</b> is responsive to a computer-readable storage medium <b>204</b> and to computer programs <b>206</b>. Computer-readable storage medium may be any local or remote device, now known or later developed, capable of recording or storing data, and in particular may be, or may include, a read only memory (“ROM”), a flash memory, a random access memory, a hard disk drive, all types of compact disks and digital videodisks, and/or a magnetic tape.

0038Computer programs <b>206</b> are generally software components implemented according to well-known software engineering practices for component-based software development and stored in computer-readable memories, such as computer-readable storage medium <b>204</b>. Computer programs <b>206</b>, however, may be any signal processing methods and/or stored instructions, in one or more parts, that electronically control functions set forth herein.

0039Network interface function <b>208</b> represents aspects of the functional arrangement of various computer programs <b>206</b> that pertain to the receipt and processing of content <b>12</b> (shown in <figref idref="DRAWINGS">FIG. 1</figref>), and messages relating thereto, as such content traverses paths of network devices, passing through, at each network interface, the seven vertical layers of the well-known abstract model that defines internetworking: layer <b>1</b>, the Physical Layer; layer <b>2</b>, the Data Link Layer; layer <b>3</b>, the Network Layer; layer <b>4</b>, the Transport Layer; layer <b>5</b>, the Session Layer; layer <b>6</b>, the Presentation Layer; and layer <b>7</b>, the Application Layer. Network interface function <b>208</b> facilitates communication between functions such as stream acquisition agent <b>70</b> (shown in <figref idref="DRAWINGS">FIG. 1</figref> and discussed further below) distribution agents <b>72</b> (shown in <figref idref="DRAWINGS">FIG. 1</figref> and discussed further below), and/or stream acquisition client <b>80</b> (also shown in <figref idref="DRAWINGS">FIG. 1</figref> and discussed further below). As such, network interface function may include data interfaces, operations support interfaces, radio frequency interfaces, and the like (implemented, for example, by routers, switches, modems, or other network connection support devices or software at each network device configured to handle communications protocols).

0040Referring again to <figref idref="DRAWINGS">FIG. 1</figref>, IP network <b>24</b> may be a regional IP network and/or IP backbone (which in practice may be included in, or separate from, headend <b>22</b> in whole or in part) using well-known components such as media gateways, signaling gateways, routers, switches, and firewalls, to produce one or more content stream(s) <b>50</b>, which represent video, audio and user data for content <b>12</b> from particular media sources that has been encoded according to one or more technologies or protocols, such as a Moving Picture Experts Group (“MPEG”) protocols (for example, MPEG-2 or MPEG-4), and delivered as one or more data streams (an MPEG-2 transport stream or an MPEG-4 elementary stream delivered via RTP, for example) to stream processor <b>26</b>.

0041Each content stream <b>50</b> includes a number of temporally spaced access points (intra-coded frames (“I-frames”) in MPEG-compressed data streams, for example), which are usable by consumer network devices to begin acquiring and rendering content carried by content stream <b>50</b>. It will be appreciated that aspects of the present invention may be applied to any number of content streams <b>50</b>.

0042Stream processor <b>26</b>, which includes or accesses the components of generic network device <b>200</b> (shown in <figref idref="DRAWINGS">FIG. 2</figref>), receives content stream <b>50</b> from IP network <b>24</b>, and manages certain features of consumer network device <b>14</b>'s access to content <b>12</b> within content stream <b>50</b> in accordance with various aspects of the present invention. Stream acquisition agent function <b>70</b> (discussed further below, in connection with <figref idref="DRAWINGS">FIG. 4</figref>) represents aspects of the functional arrangement of various computer programs <b>206</b> (shown in <figref idref="DRAWINGS">FIG. 2</figref>; in one aspect, stream acquisition agent function <b>70</b> is implemented by one or more Application Layer computer programs <b>206</b>) that pertain to the generation of broadcast streams <b>52</b> (stream<b>1</b>, stream <b>2</b>, . . . stream S) and/or schedule <b>54</b>, based on content stream <b>50</b>, and transmission to/use by consumer network device <b>14</b>. Although stream processor <b>26</b> is shown within headend <b>22</b>, it will be appreciated that stream processor <b>26</b> may be located at any local or regional distribution point associated with a broadband communication network.

0043Servers/routers <b>28</b>, which also include or access the components of generic network device <b>200</b> (shown in <figref idref="DRAWINGS">FIG. 2</figref>), are responsive to stream processor <b>26</b>. Servers/routers <b>28</b> are responsible for making appropriate broadcast stream(s) <b>52</b> and/or schedule <b>54</b>, available to consumer device <b>14</b> as one or more packet-data streams <b>30</b> via distribution agents <b>72</b> (discussed further below, in connection with <figref idref="DRAWINGS">FIG. 4</figref>).

0044<figref idref="DRAWINGS">FIG. 3</figref> is a block diagram of an exemplary consumer network device <b>14</b>, which includes or accesses the components of generic network device <b>200</b> (shown in <figref idref="DRAWINGS">FIG. 2</figref>), in/with which various aspects of the present invention may be used. Using one or more channels, protocols and/or techniques, consumer network device <b>14</b> communicates information to, and receives information from, headend <b>22</b> via HFC network <b>25</b>. For example, among other things, consumer network device <b>14</b> communicates content selection indication <b>380</b>, which may be a preliminary or final indicator of particular content <b>12</b> (a channel signal, for example) offered by the MSO operating broadband communication network <b>10</b> (shown in <figref idref="DRAWINGS">FIG. 1</figref>) that has been selected by a consumer (not shown) using any type of well-known user interface <b>304</b> such as a remote control, mouse, stylus, microphone, keyboard, or display. In response, in accordance with aspects of the present invention discussed further below, consumer network device <b>14</b> receives, among other things, one or more packet-data streams <b>30</b> that include the selected content (for example, data stream <b>30</b>, which may be or include an MPEG stream).

0045Additional communication interfaces <b>350</b> may also facilitate consumer network device <b>14</b>'s one-or two-way communication with other internal or external devices or networks thereof, such as cable modems, personal computers, data terminal equipment, telephones, media players, data storage devices, personal digital assistants, or any other IP-enabled network, device or component/combination thereof, along with associated network support devices and/or software.

0046Internal elements associated with consumer network device <b>14</b> include a tuner <b>302</b>, which includes well-known arrangements of components, operating (by tuning to a particular in-band or cut-of-band channel signal, for example) using well-known manners and techniques to receive particular information from headend <b>22</b> and/or additional communication interfaces <b>350</b>.

0047A video decoder <b>344</b> is responsive to receive and decode signals from tuner <b>302</b>. Video decoder <b>344</b> includes well-known arrangements of components, such as demodulators, responsive to receive digital signals, such as digital data packets of data stream <b>30</b>, and to output video information. Video information that may require format translation or modification for compatibility with capabilities of consumer network device <b>14</b> and peripherals thereof (not shown) may be passed to encoder <b>341</b> for formatting. Encoder <b>341</b> includes well-known arrangements of components, and operates in accordance with well-known methods and techniques.

0048Video information from video decoder <b>344</b> and/or encoder <b>341</b> may be passed to multimedia processor <b>349</b>, which is operative to perform predetermined coding techniques to arrange video information into displayable/storable formats, in accordance with well-known methods and techniques. Internal arrangements of multimedia processor <b>349</b> are well known, and may include analog-to-digital converters, general or special-purpose processors or application-specific integrated circuits such as encoder/decoder pairs (“CODECs”) (MPEG CODECs, for example), storage media and/or buffers, along with demultiplexors for demultiplexing and/or synchronizing at least two streams (for example, video and audio).

0049Stream acquisition client function <b>80</b> (discussed further below, in connection with <figref idref="DRAWINGS">FIG. 4</figref>) represents aspects of the functional arrangement of various computer programs <b>206</b> (in one aspect, stream acquisition client function <b>80</b> is implemented by one or more Application Layer computer programs) that operate to acquire and render the content selected via content selection indication <b>380</b> and carried by data stream <b>30</b>. More specifically, stream acquisition client function <b>80</b> represents functions relating to the handling of schedule <b>54</b> and/or broadcast streams <b>52</b> to enable acquisition and rendering of selected broadcast streams <b>52</b> by consumer network device <b>14</b> in accordance with various aspects of the present invention.

0050With continuing reference to <figref idref="DRAWINGS">FIGS. 1-3</figref>, <figref idref="DRAWINGS">FIG. 4</figref> is a flowchart of a method, which is operable in a broadband communication network, for delivering content, such as content <b>12</b>, to a consumer network device, such as consumer network device <b>14</b>, in accordance with certain aspects of the present invention. The method may be implemented when one or more computer programs, such as computer programs <b>206</b> associated with headend <b>22</b> (for example, stream acquisition agent <b>70</b> and/or distribution agents <b>72</b>) are loaded into a processor, such as a processor associated with stream processor <b>26</b>, and executed.

0051The method begins at block <b>400</b>, and continues at block <b>402</b>, where an original data stream, such as content stream <b>50</b>, is managed. The original data stream has original recurring access units (“RAUs”), which are usable by the consumer network device to acquire the content from the original data stream. It will be understood that RAUs may be random access units, such as MPEG I-frames, or any other element(s) or process(es) associated with a data stream that facilitate access to such data stream by receiving devices.

0052Next, at block <b>404</b>, the original data stream and original RAUs are replicated. The replicated RAUs are usable by the consumer network device to acquire the content from the replicated data stream. The replicated data stream is offset relative to the original data stream—and the replicated RAUs are offset relative to the original RAUs—by a predetermined amount of time at block <b>406</b>.

0053In one implementation associated with point-to-multipoint applications, stream processor <b>26</b> creates multiple time-delayed replicas of each content stream <b>50</b> (and thus time-delayed replicas of the I-frames associated with content stream <b>50</b>), which for one content stream are shown as broadcast streams <b>52</b> (see <figref idref="DRAWINGS">FIG. 1</figref>). Stream processor <b>26</b> determines the maximum time between consecutive I-frames in content stream <b>50</b>, and based on a predetermined number (“S”) of broadcast streams <b>52</b> (which may be specified by the MSO, for example), computes the time offset (“Δt”) between broadcast streams. That is, <maths id="MATH-US-00003" num="3"><math overflow="scroll"><mrow><mrow><mi>Δ</mi><mo>⁢</mo><mstyle><mtext> </mtext></mstyle><mo>⁢</mo><mi>t</mi></mrow><mo>=</mo><mfrac><mrow><mi>max</mi><mo>⁡</mo><mrow><mo>(</mo><mrow><mrow><msub><mi>t</mi><mi>RAU</mi></msub><mo>⁡</mo><mrow><mo>[</mo><mi>i</mi><mo>]</mo></mrow></mrow><mo>-</mo><mrow><msub><mi>t</mi><mi>RAU</mi></msub><mo>⁡</mo><mrow><mo>[</mo><mrow><mi>i</mi><mo>-</mo><mn>1</mn></mrow><mo>]</mo></mrow></mrow></mrow><mo>)</mo></mrow></mrow><mi>S</mi></mfrac></mrow></math></maths>

0054Alternatively, stream processor <b>26</b> could compute S based on an operator-specified Δt. In either case, the objective is to make Δt small enough to facilitate fast acquisition and rendering of content <b>12</b> by consumer network device <b>14</b>, while keeping S practical.

0055Stream processor <b>26</b> then forwards the original content stream (by way of example, “stream <b>1</b>” as shown in <figref idref="DRAWINGS">FIG. 1</figref> represents the original content stream) to a unique multicast destination address (“N_1”), which may be implemented/maintained using well-known methods and techniques by distribution agents function <b>72</b> and/or servers routers <b>28</b>. N₁, for example, may be advertised in the Session Description Protocol (“SDP”) for a particular session. Next, a replica of stream <b>1</b>, delayed by an amount of time Δt, is forward to a different multicast destination address (“N_2”), which could also be included in the SDP, or, alternatively, a relationship to N₁could be established a priori. In general, each replica stream, “Stream k,” is delayed (k-<b>1</b>) Δt relative to content stream <b>50</b>, and sent to multicast address N_k, where 1≦k≦S.

0056In addition, stream processor <b>26</b> creates schedule <b>54</b>, which may contain, among other things: (1) certain global information, such as an NTP timestamp (eight bytes), which represents the NTP wallclock time at which schedule <b>54</b> is delivered into network <b>10</b>; and (2) certain information associated with each content stream <b>50</b>/service available for selection by consumer network device <b>14</b>. For example, for each content stream <b>50</b> and its associated broadcast streams <b>52</b>, the following information may be included in schedule <b>54</b>: the time at which the current RAU for stream <b>1</b> was delivered into network <b>10</b> (which may be expressed as a two-byte two's-complement offset in milliseconds relative to the NTP timestamp); the time at which the next RAU for stream <b>1</b> will be delivered into the network (which may also be expressed as a two-byte two's complement offset in milliseconds relative to the NTP timestamp); the time offset (Δt) between streams (which may be expressed in milliseconds using one-byte); and the number of available broadcast streams <b>52</b> (which may be a one-byte value).

0057The foregoing discussion assumes that stream processor <b>26</b> and consumer network device <b>14</b> are synchronized to a common NTP timebase. It is also possible, however, to employ Real Time Streaming Protocol (“RTSP”) Sender Reports (or features of a similar protocol) to achieve similar functionality. Sender Reports relate an absolute time (usually, but not necessarily, NTP time) to a relative time (Real-time Transport Protocol (“RTP”) timestamps, for example) for each content stream <b>50</b>, allowing a consumer network device to compute the relative offset between streams, and thus the time of the next available RAU for a particular content stream.

0058At block <b>408</b>, it is arranged for the predetermined amount of time from block <b>406</b> to be communicated to the consumer network device. As is shown in block <b>410</b>, the predetermined amount of time is usable by the consumer network device to determine whether a next available RAU is one of the original RAUs or the replicated RAUs, and the next available RAU is usable to acquire the content (content acquisition is discussed further below, in connection with <figref idref="DRAWINGS">FIG. 5</figref>).

0059With continuing reference to <figref idref="DRAWINGS">FIGS. 1-3</figref>, <figref idref="DRAWINGS">FIG. 5</figref> is a flowchart of a method, which is operable in a broadband communication network such as network <b>10</b>, for receiving content such as content <b>12</b>, in accordance with certain aspects of the present invention. The content is carried via both a first data stream and a second data stream, and both data streams have RAUs offset relative to each other by a predetermined amount of time. The method may be implemented when one or more computer programs, such as computer programs <b>206</b> associated with consumer network device <b>14</b> (for example, stream acquisition client function <b>80</b>) are loaded into a processor, such as a processor associated with consumer network device <b>14</b>, and executed.

0060The method begins at block <b>500</b>, and continues at block <b>502</b>, where it is arranged for receipt of a schedule via a first multicast IP address. The schedule includes a first time value representing a past time at which an initial RAU associated with the first data stream was broadcast, and a second time value representing a future time at which a subsequent RAU associated with the first data stream will be broadcast, and also includes the predetermined amount of time.

0061In one implementation, consumer network device <b>14</b> joins the multicast group for schedule <b>54</b> using a Network Layer multicast protocol such as Internet Group Management Protocol (“IGMP”) (via issuance of an IGMP Join message for the multicast group for schedule <b>54</b>, for example). The IP address of the multicast group for schedule <b>54</b> may be advertised by headend <b>22</b> (via distribution agents function <b>72</b> and/or servers/routers <b>28</b> using SAP/SDP, for example), or may be configured a priori, such as during initial consumer device <b>14</b> configuration. Consumer network device <b>14</b> remains tuned to the multicast group for schedule <b>54</b> indefinitely.

0062At diamond <b>504</b>, based on the schedule, it is determined whether a next available RAU is associated with the first data stream or the second data stream. If the next available RAU is associated with the first data stream, then, at block <b>506</b>, the first data stream is selected from which to receive the content, and if the next available RAU is associated with the second data stream, then, at block <b>508</b>, the second data stream is selected from which to receive the content.

0063In implementation, the information in schedule <b>54</b>, possibly considering specified or estimated delays, is used by consumer network device <b>14</b> to determine the next available I-frame, and a particular stream may be selected/received by issuing an IGMP Join for the multicast group associated with the stream having the next available I-frame. An IGMP Leave may be necessary to leave the preceding multicast group and free up sufficient bandwidth to receive the selected content.

0064To further decrease the time required to acquire and render content <b>12</b>, if a consumer operates user interface <b>304</b> in a manner that indicates service selection is monotonically increasing or decreasing (that is, the consumer is “channel surfing”), consumer network device <b>14</b> could “arm” itself using information in schedule <b>54</b> for the next highest and next lowest channels, rather than waiting for the eventual content selection to be made. Similarly, if a consumer enters a channel selection by keypad, consumer network device <b>14</b> could pre-process the schedule information for the ten channels remaining before the last key press. For example, assuming the desired channel is <b>206</b>, then schedule information for channels <b>200</b> through <b>209</b> could be obtained immediately after the consumer enters digits ‘2’ and ‘0’.

0065Thus, apparatuses and methods have been presented that minimize delays associated with a consumer network device's acquisition of different content (channel change delays, for example) in multicast environments such as broadcast video or certain video-on-demand applications. A consumer network device may compute and select a multicast stream with the nearest next access opportunity, and bandwidth penalties associated with carrying additional recurring access units such as I-frames within a data stream are avoided. Assuming six bytes per channel, a schedule message rate of two per second, and 100 content streams, the required bandwidth for the schedule stream would be approximately 10 kbps.

0066A variation using unicast point-to-point connections and two-way protocols (such as RTSP or RTSP-like protocols) is also possible. A functional block diagram of a stream processor <b>26</b> (which may also include or access elements of generic network device <b>200</b>, shown in <figref idref="DRAWINGS">FIG. 2</figref>) in accordance with aspects of the present invention associated with this variation is shown in <figref idref="DRAWINGS">FIG. 6</figref>. As shown, stream processor <b>26</b> receives N content streams <b>50</b>, and each is sent to its own circular buffer <b>602</b>. Circular buffers <b>602</b> may be implemented using well-known structures, methods and techniques.

0067A content router <b>604</b>, which includes or has access to stream acquisition agent function <b>70</b>, is responsible for retrieving content from any of these buffers and sending it as broadcast stream <b>52</b> to a specific consumer network device, such as consumer network device <b>14</b>.

0068With continuing reference to <figref idref="DRAWINGS">FIGS. 1-3</figref> and <figref idref="DRAWINGS">FIG. 6</figref>, <figref idref="DRAWINGS">FIG. 7</figref> is a flowchart of a method, which is operable in a broadband communication system, for delivering content to a consumer network device, such as consumer network device <b>14</b>. The content is carried by a data stream having recurring access points such as I-frames. The method begins at block <b>700</b>, and continues at block <b>702</b>, where notification of content selection activity initiated by a consumer network device is received.

0069In one possible implementation, stream processor <b>26</b> shown in <figref idref="DRAWINGS">FIG. 6</figref> is responsible (via stream acquisition client function <b>80</b>) for communication with consumer network device <b>14</b> (using RTSP, for example) to determine the particular content stream <b>50</b> desired by the consumer network device that should be sent (for example, unicast) as broadcast stream <b>52</b>—content selection indications <b>380</b> (shown in <figref idref="DRAWINGS">FIG. 3</figref>) made by the consumer propagate back to stream processor <b>26</b>, and are received by stream acquisition agent function <b>70</b>.

0070At block <b>704</b>, communication with a circular buffer is arranged based on the content selection activity. The circular buffer has at least part of the data stream inserted therein, with at least one RAU. Next, at block <b>706</b>, determination of a next available RAU within the circular buffer is arranged, and at block <b>708</b>, it is arranged for delivery of a data packet including the next available RAU to the consumer network device.

0071In implementation, stream acquisition agent function <b>70</b> may be responsible for communication with content router <b>604</b> (via a media server/client interface, for example), instructing content router <b>604</b> to cease streaming content from one circular buffer <b>602</b>, and to begin streaming content from the desired circular buffer <b>602</b>. Content router <b>604</b> communicates with each circular buffer <b>602</b> to determine the memory location of the most recent RAU for each stream. Circular buffers <b>602</b> need only be large enough to retain the maximum number of bytes expected between consecutive RAUs. Content router <b>604</b> is responsible for switching streams distributed to consumer network device <b>14</b>, and unicasting the content therefrom to individual consumer network devices, ensuring that the first data packet delivered to consumer network device <b>14</b> after a content change request includes a RAU.

0072Thus, at the expense of some increased complexity, the foregoing approach would facilitate the near immediate delivery of an access point to a consumer network device when a content selection request is received if the number of consumer network devices is limited to a practical number, and would make content selection mostly transparent to the underlying network (for example, the need for transmission of an additional schedule, such as schedule <b>54</b>, to a consumer network device is obviated).

0073Aspects of the present invention described herein address the needs for bandwidth-conserving methods and apparatuses that allow accelerated acquisition and rendering of encoded content configured for broadcast distribution via packet data communication technologies to consumer devices within broadband communication networks. One or more processors packaged together or with other elements of central or regional network elements or consumer network devices may implement functions described herein in a variety of ways. It will be appreciated, however, that aspects of the present invention are not limited to any specific embodiments of computer software or signal processing methods—functions described herein are processes that convey or transform data in a predictable way, and may generally be implemented in hardware, software, firmware, or any combination thereof.

0074Moreover, although certain functions herein have been referred to as “agents” and “clients”, such functions need not be implemented using traditional client-server architectures in which computer application programs are configured to cause clients, such as consumer devices, to request services from server-based service providers in a network such as the Internet, but may be implemented in any suitable manner.

0075When one element is indicated as being responsive to another element, the elements may be directly or indirectly coupled. Connections depicted herein may be logical or physical in practice to achieve a coupling or communicative interface between elements. Connections may be implemented as inter-process communications among software processes.

0076It will furthermore be apparent that other and further forms of the invention, and embodiments other than the specific embodiments described above, may be devised without departing from the spirit and scope of the appended claims, and it is therefore intended that the scope of this invention will be governed by the following claims.