CA2466458A1 - Fast start-up for digital video streams - Google Patents

Abstract

Described herein is a technology facilitating the presentation of digit al video streams. An implementation, described herein, reduces the effective start-up delay in the presentation of the first frames of the video content that occu rs when a system tunes into a video stream. This abstract itself is not intended to limit the scope of this patent. The scope of the present invention is pointed out in t he appending claims.

Description

FAST START=UP FOR DIGITAL VIDEO STREAldIS
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TECI~NICAL FIELD
~i This invention generally relates to a technology for digital video streaming.
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BACKGROUND

With advent of digital video streaming technology (such as video-on-s demand (VOD) systems), users are able to see and hear digital videos, more or 9 less, as the data is being received from a video server.
,0 SNhen video is streamed, the incoming video stream is typically buffered on ~ ~ the user's receiving device (e.g., computer or set-top box) while data is ,z downloaded into it. At some defined point {generally, when the buffer is full), the ,3 video contents are presented to the user. As the video content plays, the receiving ~a device empties the data stored in the buffer. However, while the receiving device l; is playing the stored video, more data is being downloaded to re-.fill the buffer. As ;6 long as the data can be downloaded at least as fast a.s it is being played back, the m ~' file will play smoothly.
~s ;~ ~~ PEG
zo ~ The predominant digital video compression and transmissi~n farmats are zl from a family called MPEG (Moving Picture Experts Group). It is the name of zz, family of standards used for coding audio-visual information (e.g., movies, video, 23 ~~ music, and such) in a digital compressed format.
za For the convenience of explanation of video streaming, the MPEG-family z; video stream is generally discussed and described herein. However, those who are M S 1-i 432US i 0610030857 MS 1-1432US.PAT APP.DOC
lee~hayes We sos.3:<-rae Atty: kasey chtistie CA 02466458 2004-05-05 ' 1 skilled in the art understand and appreciate that other such digital video 2 compression and transmission formats exist and array be used.
Of course, there are other digital video compression and transmission a formats, such as the I=1.264 codec. Those of -ordinary skill in", the art will understand how the concepts discussed herein with relationship to MPEG apply to 6 ~~ other formats.
m 8 i~ GOP and Frames A II~IPEG video stream is typically defined by a series of segments called ,o Groups of Pictures (GOP). Typically, a GOP consists of a set of pictures intended ~ to be displayed in sequence over a short duration (e.g., %2 second) when displayed z at their intended speed.
A GOP typically includes three types of frames:
a ~ an intra frame (I-frame);
,; ~ predictive frames (P-frames); and ;6 ~ bi-directionally predictive frames (B-frames).
m There is no specific limit to the number of frames which rnay be in a GOP, is ~~ nor is there a requirement for an equal number of pictures in alI GOPs in a video i9 » Se~llen~e.
Zo The I-frame is an encoded still image. It is nondependent upon any other ai frame that the decoder has already received. Each GOP typically has only one I-Zz frame. It is sometimes called a random access point (or "RAP") since it is an entry 23 point for accessing its associated GOP.
z4 From the point of view of a video-stream decoder, fhe P-frames are Zs predicted from the most recently reconstructed I- or I'-frame. A lP'-frame (such MS1-1432US 2 06f0030857MS1-1432US.PArAPPOOC
~eee~aYes w~ sos.sz<.vise Aly: kasey christie t as frame 120p} requires data from a previously decompressed anchor frames (e.g., z I-frames or I'-frames) to enable its decompression.
Switching to the point of view of video stream encoder and transmitter, the a B-frames are predicted .from the closest two I- or F-frames--~-one _ frame in the s past and one frame in the future. A B-frame (such as frame 132p) requires data 6 fro~-~ both preceding and succeeding anchor frames (e.g., I-frames or ~'-framesl to decode its image. It is bi-directionally dependent.
s Of course, other digital video compression and transmission formats (such 9 as H.264 codec) may employ other labels, some different type,, and different to relationships between frames. For example, in H.264, the frame types, frame dependence relationships, and frame ordering are much more decoupled than they ~z are in MPEG. In H.264, the I-frames are independently decodable and are i 3 random access points. Also, frames have defined presentation order (like MPEG
~a. does). However, the other frames relate differently than do the MPEC ~-frames i; and B-frames.
is So, those of ordinary skill in the art will understand how the concepts ~ discussed herein with relationship to MPEG apply to other formats.
rs 9 ~! Transmission and Presentation Timelines zo Fig. I illustrates two manifestations of the same MPEG video stream. The z~ first is the transmission timeline 100t and the other is the presentation timeline zz I ~ I 00p.
z; The transmission timeline 100t illustrates a video stream from the 24 perspective of its transmission by a video-stream encoder and transmitter.
zs M S ~ -14 32 U S 3 Ofi10030857 MS J-1432US PAT APP. DOC
k9~hayes o~ sov.3aaaxss Ariy: kasey chtistia Alternatively, it may be viewed from the perspective of the receiver of the z transmission of the video stream.
As shown in Fig. I, the I-frames (e.g., IIOt and 150t) are typically 4 temporally longer than the other. frames in the transmission tim.e~line.
Since it daesn't utilize data from any other frame, it contains all of the data necessary to s produce one complete image for presentation. Conseq~~ently, an I-frame includes more data than any of the other frames. Since the I-frame has more data than 8 others, it follows that it typically requires greater tine for transmission (and, of 9 course, reception) than the other frame types.
o Fig. 1 also shows P-frames (such as 120t) and 3~-frames (such as 130t and n 132t) of the transmission timeline I00t. Relative to the L-~-frames, the P-frames 2 are temporally longer in the transmission timeline because they typically include ~3 :more data than the B-frames. I~owever, P-frames are temporally shorter than I-~ frames because they include less data than I-frames. Since the P-frames rely on ~; data from at least two other frames, they typically do not need as much data of I6 their own to decode their image as do P-frames (which rely on one other frame).
Fig. 1 also illustrates the presentation timeline 100p of the video stream I$ from the perspective of its presentation by the video decoder and presenter. In 19 contrast to their transmission duration, the presentation duration of each frame-zo regardless of type-is exactly the same. In other ~~rords, it displays at a fixed 21 frequency.
zz 'The incoming frames of the video stream are decoded, buffered, and then z3 presented at a fixed frequency (e.g., 24 frames per second (fps)) to produce a za relatively smooth motion picture presentation to the user. In MPEG 2 used to z; convey NTSC video, the Field rate is fixed, and each MPEG 2 picture may produce MS1-1432US 4 p61Q030857MS1-1432US.PATAPP.DOC
Iee~heYes a~ sos.3xn.y~se Atty: kasey chrisfie 1, 2, or 3 fields. Field pictures are required to produce 1 field, and frame pictures z may produce 2 or 3 fields. Thus, the frame picture presentation rate may not be 3 fixed, but it is not dictated by the transmission rate of the frame pictures.
Fig. 1 also illustrates a typical decoded GGP 105 of MPEG in its s presentation timeline. This G~P example includes an I-frame IIOp; six ~.'~
6 frames (e.g., 120p); and 1~ ~-frames (e.g., 130p and 132p). Typically, each GOP
7 includes a series of consecutively presented decoded frames that begin with an I-8 frame (such as frame 110p).

Order of Transmission and Presentation ~o a As shown in Fig. 1, the order in which the frames are presented typically ~z does not directly match the order in which the frames are transmitted. The arrows i 3 shown in Fig. 1 between the frames of the transmission timeline 100t and the a presentation timeline 100p illustrate a typical way that frames are reordered is between reception and presentation. The tail of each arrow has a bullet (i.e., circle) r s anchor at the end of a transmitted frame. The head of each arrow has an i 7 arrowhead pointing to its corresponding presentation frame.
is For example, the transmission I-frame 1 IOt corresponds to the presentation m I-frame 110p. In reality these are the same frames, but their timeline zo representations indicate their.different manifestations.
z~ Returning to the explanation of this example, the transmission h-frame zz 120t corresponds to the presentation ~'-frame 120p. The transmission ~-frames z; 130t and 132t corresponds to the presentation ~-frames 130~p and 132p. As z4 shown in Fig. I, these ~3-frames I30t and 1321 are encoded, transmitted, received, zs and decoded after their P-frame 120t in the transmission timeline 100t, but their M ~J 1-1432 U S 'rJ 0610030857 MS 1- >432US. PAT APP. DOC
lee~haYes c~ saraa,.szss Atty: kasey cMistie corresponding presentation :~-frames 130p and 132p are presented before their z L'-frame I20p in the presentation timeline 100t. Note that the encoder typically 3 receives the frames in non-compressed form in the same order that the frames are 4 eventually displayed, and the encoder typically performs the frame re-ordering s before compressing the frames.
s , Fu~ h4~°~ncre, the next GOP tc be transmitted starts with I-frame I50t, bat two B-frames 134t and 1361 typically come along after this new 4~rOP has begun.
s As illustrated in Fig. I, the straggling B-frames I34p and l3bp are presented in 9 sequence and before the presentation of the I-frame 150p of the new GOP.
~o GOP Presentation Delay a rz Fig. I shows that the I-frame 1101 of an example GOP is first received j3 beginning at point 'fl. iri time; however, it is not first presented until point Tz. The ~a time gap between the two points is called herein the "GOP presentation delay" and 1 > is labeled 170 in Fig. I . It represents the delay from when the receiver first begins ;s receiving the first frame of a GOP (which is typically the I-frame) until the device ~ first presents the first frame of the GOP.
is There are many reasons for this delay. Some are a natural consequence of 9 the video streaming technology and others are imposed into the process to address zo known technical issues. Some of reasons for the GOP' presentation delay include:
zr ~ contrast between the time required to receive a frame transmission zz and the time required to display a frame;
z3 ~ the time required to decode a frame (especially considering inter-za frame dependencies for decoding); and M S 1-14320 S 6 p670030857MS7-7432US.PATAPP DOC
Atty: kasay ch~istie ~ built-in delay to facilitate smooth presentation of frames without z needed to wait for frame transmission or decoding.
The details of these reasons and the knowledge of other reasons are known 4 to those-~of ordinary skill in the art.
si ~lideo-Stream Presentation Mart-up Delay To tune channels in a video-streaming environment (such as digital cable), s a receiver receives a video stream and waits for an access point into the stream. A
9 channel change cannot occur until an access point is received. From the ~o perspective of the user, this can lead to lengthy channel change times.
n Fig. 2 illustrates an example of a video-stream presentation start-up delay at ,z 280. The start-up delay is the effective delay experienced by a user. It includes a ~ 3 ~ delay between when a . particular video stream i s requested and the actual ,4 presentation of the first frame of a GOP from the particular video stream.
As is shown in Fig. 2, the start-up delay 280 includes the GOP presentation delay 6 (discussed above).
m Referring to Fig. 2, this example is explained. A GOP, starting with I-8 frame 210t, is being transmitted. This is shown in the transmission timeline 200t.
9 The receiver tunes into this video stream at request point IZ. This selection is zo illustrated as a user selecting a video-strearri channel using a remote control 260.
z~ Again, this is an example illustration for explanatory puzpose. This point R
zz I could be at any moment in time after the beginning (i.e., after the beginning of its z3 I-frame 210t) of a GOP.
za The receiver must wait for a random access point (or RAP) in order to zs access the video stream. In this example, each GOP has one RAP. An I-frame is MSS-1432US 7 061003Q857MSi-1432US.PATAPPOOC
lee~hayes ,~ sarsx<.sxse Atty: kasey christie i an example of a typical RAP. Therefore, each GOP has one I-frame. So, the z receiver must wait for the next I-frame (at the beginning of the next GOP) before 3 it can access the video-stream transmission as shown by transmission timeline 4 2'OOt.
s Once the receiver has an I-frame in its buffer, it may refer back to it for dependency decoding of I'- and ~-frames. Consequently, a conventional system must wait for a RAP before it can start buffering frames (that are useful).
s In Fig. 2, the receiver starts buffering the next GOP at point M1 with I-9 frame 250t. Thus, the first frame that may be eventually presented to the user is I-io frame 2501, because it is the f rst IZAP in the stream after the point at which the ~ receiver joined the stream. Because of the GOP presentation delay (discussed iz above), it actually starts presenting the GOP (with I-frame 250p of presentation 13 timeline 200p) at point MZ-which is also the presentation start-up point S
of the la start-up delay 280.
s As demonstrated by the screens 262-266, the start-up delay is the effective is delay experienced by a user. The user selects a video-stream channel at request point IZ (using, for example, a remote 260) and sees a blank screen, as shown by is screen 262. Of course, there may be information presented here (such as i9 electronic programming information), but since it is not yet the desired video-O - strearri content it is effectively blank.
z~ Screen 264 shows that screen remains blank even after the next GOP is zz currently being received. Screen 266 shows that the first image of frame 250p is z3 finally presented to the user.
z4 The average length of this start-up delay is directly proportional to the zs average GOP length. Some video-stream providers employ relatively Long average M S 1-1432US 8 06100,?OHS~AtS7-1432US.PATAPP DOC
Iee~haYes w~ sae.~aaass Aty: kasey chtistie i GOF lengths. For these instances, this delay is even more acute because the user is z waiting longer for the next CDP to come round after sh:e has changed channels.
It short, this start-up delay is very annoying to the typical users and tries ~ ~) their patience.
si SUMMARY
Described herein is a technology facilitating the presentation of digital g video streams. An implementation, described herein, reduces the effective start-up 9 delay in the presentation of the first frames of the video content that occurs when a ~o system tunes into a video stream.
This summary itself is not intended to limit the scope of this patent.
iz Moreover, the title of this patent is not intended to limit the scope of this patent.
~3 For a better understanding of the present invention, please see the following detailed description and appending claims, taken in conjunction with the a; accompanying drawings. The scope of the present invention is pointed out in the ;5 appending claims.
l8 ~~ BRIEF DESCRIPTION GF THE DRAWINGS
;s The same numbers are used throughout the drawings to reference like zo elements and features.
z~ Fig. 1 is diagram illustrating a typical video stream transmission timeline zz and its corresponding presentation timeline.
z~ Fig. 2 is diagram illustrating the presentation start-up delay using a typical za video stream transmission timeline and its corresponding presentation timeline.
zs P1/( S 7 -1432 U S 9 0610030857 MS 1-1432US.PAT.APP.OOC
lee~heyes o~ sos~3x~.sxss Atty: kasey christie r Fig. 3 is diagram illustrating the new presentation start-up delay in z accordance with an implementation, described herein, that employs a single 3 alternative video-stream.
Fig. 4 is diagram illustrating the new presentation start-up delays in accordance with another implementation, described herein, that employs multiple 6 i alternati~Je video-streams.
Fig. 5 is a flow diagram showing a methodological implementation s described herein.
Fig. 6 is a flow diagram showing a methodological implementation to described herein.
Fig. 7 illustrates exemplary environment in which an implementation ~z described herein may be employed.
-3 l~_ig. 8 illustrates of an example presentation device, a television, and ,a various input devices that interact with the presentation device.
a; Fig. 9 is a block diagram that illustrates components of the example is presentation devices) shown in Figs. 7 and 8.
8 ~~ DETAILED DESCItIPTI~N
19 In the following description, for purposes of explanation, specific numbers, zo materials and configurations are set forth in order to provide a thorough ~ understanding of the present invention. However, it will be apparent to one skilled zz in the art that the present invention may be practiced without the specific z3 exemplary details. In other instances, well-known features are omitted or za simplified to clarify the description of the exemplary implementations of the zs present invention, and thereby, to better explain the present invention.
MS 1-~ 432 ICJ 1 ~ 061p030857MS 1-7432USPATAPP.OOC
lee~lhayes oec soø3x<-s2ss Atty: kasey christie Furthermore, for ease of understanding, certain method steps are delineated as z separate steps; however, these separately delineated steps should not be construed 3 as necessarily order dependent in their performance.
The ~fo?.lowing description sets ~ forth one or more exemplary ; implementations of a Fast Start-up for Digital Video Streams that incorporate 6 clcments recited in the appended claims. These implementations are described with specificity in order to meet statutory written description, enablement, and $ best-mode requirements. However, the description itself is not intended to limit the scope of this patent.
n The inventors intend these exemplary implementations to be examples. The ,1 inventors do not intend these exemplary implementations to limit the scope of the ,2 claimed present invention; rather, the inventors have contemplated that the 13 claimed present invention might also be embodied and implemented in other ways, la in conjunction with other present or future technologies.
1; An example of an embodiment of a Fast Start-up for Digital Video Streams r 6 may be referred to as an "exemplary fast start-up system."
For the convenience of explanation, digital video streams are discussed and is described herein in terms of the ~IPEG-family standard format. However, those ~ who are skilled in the art understand and appreciate that other such digital video zo coriipression and transmission formats exist.

22 ~) Introduction 2~ The one or more exemplary implementations, described herein, of the za present claimed invention may be implemented (in whole or in part) by a MS 1-1432US 11 0610030857MS7-1d32USPATAPP.DOC
k~e~IhaYes peg soøat.-s2ss Atty: kasey christie presentation device 708 (of Figs. 7-9) and/or as part of a computing environment z like that shown in Fig. 7.
To tune channels in a digital video multicast (e.g., IP multicast) environment, a receiver receives a rriulticast video data stream and waits. -for an s access point into the stream. 'This is sometimes called a random access point s (?~4P). A channel change cannot occur until a IZ.~P is received. Th~~s nay Iead to Lengthy channel change times.
A multicast environment is an example of one type of environment that 9 employs video streaming. Such an environment may utilize Internet Protocol o multicasting (i.e., IP multicasting). 'those of ordinary skill in the art are familiar ~ ; with multicast and its use in a multicast environment.
~z In many IP multicast scenarios, there is a limited bit-rate available to the I3 client device (i.e., a receiver). The bit-rate used to the client device typically a depends on which IP multicasts the client is currently listening to among all is available iP multicasts.
ib Because the total number of ongoing IP mul.ticasts is not limited by the ~ available bit-rate to any particular client, the exemplary fast start-up system is ,s particularly applicable to such a scenario. ~ne may multicast multiple join-in 19 streams (e.g., alternative transmissions 402-207) and a main stream at all times.
zo Furthermore, individual client device may determine for themselves which stream zi to be listening to at any given point. Also, the bit-rate of the main stream may be zz as high as the connection to the client device can support-so, a relatively highan z3 apparent steady-state video quality may be achieved.
za As shown in Fig. 3, the exemplary fast start-up system employs a main zs multicast video stream transmission 3001 and one or more alternative multicast MS 1-1432US 12 0670030857 MSl~7432US.PAT:APPDOC
Iee~haY6s o~ sos.aa~.szss Atty: kasey Gxistie lead-in video stream transmissions (such as transmission 302t) to achieve a faster z tuning time. 'These alternative streams include the sa.rne original content as the 3 main stream, but they may have a lower bit-rate than the main stream.
The alternative streams may be loci bitrate so that: they may be transmitted in less time than is required to transmit the main stream. This is graphically 6 ~ illastrated by alternative video-stream transmission 302t being shorter than the corresponding frames in the main video-stream transmission 300t. Herein, the a concept of "low bitrate" is in terms of number of bits per picture (i.e., frame).
9 These may be a normal bitrate in terms of the number of bits per second.
to With the exemplary fast start-up system, the video stream content is presented more quickly (than conventional approaches) in response to a tuning j z command-even if the initial picture is of lesser quality.
13 While much of the discussion of the exemplary fast start-up system is ~ framed within terms of the N1PEG family of digital video compression and 1; transmission formats, those of ordinary skill in the art will understand how the ~6 concepts discussed herein with relationship to NIPEG~ apply to other formats, such o as 1-I .2 b4.
~s Exemplary Fast Start-u~ System with ~ne Alternative Strearra ~s zo Fig. 3 illustrates the exemplary operation of the exemplary fast start-up ii system with only one alternative video-stream. Fig. 3 shows the main multicast zz video stream transmission 300t and the alternative multicast lead-in video stream z3 transmission 302t. Although this discussion refers to the use of only one z4 alternative stream, the bulk of the concepts illustrated in this example apply the zs ~I use of multiple alternative video-streams.
MS1-1432US 13 0670030857MS1-1432US.PAT.APP.DOC
~~Y~ at sos~~e.s~se Airy: kssey christie I Fig. 3 also illustrates how dais operation reduces the apparent video-stream z presentation start-up delay-which is the effective delay experienced by the user.
3 This start-up delay is the delay between the time a particular video stream is a req~:ested and the actual presentation of the first. frame-of a GOP.
s Referring to Fig. 3, this example is explained. A GOP starting with I-o,~ frame 3101 is transmitted in the main stream 300t. '1'he receiver t~~nes into this video stream at request point R. This selection is illustrated as a user selecting a s video-stream channel using a remote control 360. (1-lowever, in a multicast environment this stream 300t is requested, but since the receiver is not yet tuned Io in, the stream may not achzally be transmitted to the receiver until some point after Il R.) IZ Again, this is an example illustration for explanatory purpose. This point R
13 could be at any moment in time within a GOP after its beginning (i.e., after the o beginning of its I-frame 310t).
Is The receiver typically waits for a random access point (or RAP) in order to cs access a video stream. (ln this example, each GOP is assumed to have one RAP.) m An I-frame is an example of a typical RAP. So, the receiver must wait for the I$ next ~-frame {at the beginning of the next GOP transmission) before it can access !9 a vlde0-Stream transmission and present the video.
ao With conventional approaches, the wiser would start seeing the video zl presentation (as shown in presentation timeline 300p) upon the presentation of the 22 first I-frame 350p at point MZ. Therefore, the conventional presentation start-up zs delay (D) would be the difference between the request point (R) and point MZ.
as Written as an equation that is M s 1-1432US 14 0610030857MS1-1432USPATAPP.DOC
Atty.: kasey christie I)-Mz-R [1~
z ~~ Conventional Presentation Start-up l7elay However, instead of waiting for 'the next RAP in . the : main stream s transmission 300t, the exemplary fast start-up syste»a tunes into the alternative b r~ideo-stream transmission 3021. It starts receiving this r'=OF transmission at point -r ~1. The RAP of alternative transmission 3021 is I-frame 312t; therefore, it can s begin presenting the alternative presentation timeline 302p with presentation I-9 frame 312p at point S'.
io While alternative video-stream is presented (as shown in presentation ~, timeline 302p), the exemplary fast start-up system requests that the multicast >> router switch the receiver to the main stream multicast transmission 3001 at the i3 next RAP (e.g., I-frame 350t) of the main stream.
i4 While alternative video-stream is presented (as shown in presentation 1; timeline 302p), the exemplary fast start-tzp system starts receiving main video-16 stream transmission 300t starting with the first frame (e.g., I-frame 3S0t) of the l next GOI' of the main stream. In Fig. 3, the first frame (e.g., I-frame 350t) of the is next GOP starts at point a. Point B on the timeline represents the end of the ;~ I reception of the last frame of the alternative stream transmission 302t.
zo The switch-over from the alternative stream transmission 302t back to the zl main stream 300t occurs during or around the gap between points B and 1'~It in Fig.
zz 3. An exaggerated and visible gap between these points is shown in Fig. 3 to z3 illustrate that there is a clear opportunity for the exemplary fast start-up system to z4 join the main stream. In reality, points B and 1VI1 may occur very nearly zs M S j -14 32 U S 15 0610030857 MS 1-143ZUS. PAT APP. DOC
Ieet~lhaYes w~ sas.axe-nss Atty: kasey cnristie concurrently and may indeed be concurrent. It is possible in some embodiments to z have an small overlap so that point occurs shortly after point lVli.
At point IVI2, the exemplary fast start-up system starts presenting main a video-stream presentation 300p starting w,th the first frame (e.g., I-frame 350p) s of the next GOP of the main stream. This starts immediately after (or very nearly 6 , so; the presentation of the last frame (e.g., frame 322p~ of the alternative stream presentation 302p. This presentation switch-over point is designated in Fig. 3 at s point IVIz.
To accomplish switch-over, it may be desirable for the main stream be io tagged for splicing. Alternatively, the RAP locations within the maim stream may ~ ~ be conveyed to the multicast muter via some other mechanism. Furthermore, it ~a may be desirable for the router have an extension to normal IP multicast so that it 13 starts delivering the main stream multicast transmission when the next RAP
in the j4 main stream multicast arrives.
as Although not necessarily required, it is desirable for the presentation of the I6 alternative stream 302p to be timed so that the fast frame presented (e.g., frame m 322p) is presented immediately before the presentation of the first frame (e.g., ~s frame 350p) of the main stream presentation 300p. I3oing so enhances the smooth a presentation of the video content-in particular, it smoothes the presentation of the zo s~.-itch-over from the alternative to the main stream presentations at point M2.
zi As demonstrated by the screens 362-366, the start-up delay is the effective z2 delay experienced by a user. The user selects a video-stream channel at request z3 point R (using, for example, a remote 360) and sees a blank screen, as shown by za screen 362. Of course, there may be information presented here (such as PI1 J 1-i 432 US 16 08100.?0857 MS 1.1432US.PAT.APP.DOC
kie~lheyes ok sos.nasxss Ariy: kasey christie electronic programming information), but since it is not yet the desired video-z stream content it is effectively blank.
Screen 364 shows that screen remains blank even as the RAP of the a alternative stream 3021 is being transmitted and received::l-Iowever, screen s shows that the first image of frame 312p is presented to the user.
~~'ith the exemplary fast start-up systerra~ (as shown in Eig. 3), the ~asPr first experiences the presentation of the video content (as shown in alternative s presentation timeline 302p) upon the presentation of the first I-frame 312p at 9 point S'. Therefore, the new presentation start-up delay (D') would be the to difference between the request point (Fg) and presentation of the alternative stream 1 ~ at point S'. Expressed as an equation, that is l2 D' = S' -..1~ [2]
m New Presentation Start-up Delay m The time-savings effected by the exemplary fast start-up system is the r ~ difference between the D' and D. Using equations 1 and 2, that time-savings may a be expressed as this equation:
i9 2G ~_D~~.~2'Ss zi Time-savi~ags zz z3 With the exemplary fast start-up system, the user experience is improved z4 because the new start-up delay (D') is less than the conventional start-up delay (D) z> (i.e., D' < D). The exemplary fast start-up system improves the user's experience S 1-~'~32 U S ~ ~ 0610030857A.fSl-1432US.PAT APP.OOC
lee~lhayes c« sos.uamss Atty: kasey christie 1 by decreasing the effective start-up delay experienced by the user when compared to the delay experienced using conventional approaches.

4,~ Exemplary Fast Start-up Sy~tem with li'Iuttiple Alternative Strieams s To further minimize the start-up delay, the exemplary fast start-up system , may account for the randomness at which a L,ser tunes into a video-stream channel by employing multiple alternative, RAP phase-staggered video-stream s transmissions.
9 Fig. 4 shows the main multicast video stream transmission 400t and phase-lo staggered multiple alternative lead-in video-stream transmissions 402t-407t. Each ~ t altemativ a transmission may be sent using all of the available bandwidth-thereby ~2 minimizing transmission time for each stream. Also, the transmission schedule of a the streams are phase-staggered so that the completed reception of each stream's ~a RAP is staggered. Since the RAP of each of the streams illustrated in Fig.
4 is at a; the beginning of the transmissions, the beginning of each of the transmissions 16 402t-407t is staggered. 'This staggered start of the alternative transmissions is m illustrated in Fig. 4.
Furthermore, the time range of phase-staggering of the alternative streams ~9 402t-407t is between RAPS of the main stream transmission 400t. In Fig. 4, this is Zo illustrated by the phase-staggering bet\veen ~-frames 4I Ot and 450t.
z~ ~y sending multiple different streams, tuning time is improved because the 22 receiver may select one of the lead-in streams to play. The one selected will z3 typically be the one which will be ready to be presented the quickest after the time Za at which the user tunes.

M S 1-~ 432U S 18 06 )0030857 MS J- t432US.PArAPP DOC
IeeQlhayes ~ sos.ma.szss Atty: kasey christie These alternative transmissions need not be sent concurrently to a particular z receiver within a multicast environment. P-ather, each one is prepared for 3 transmission, but a particular multicast stream is sent to a particular recei~rer only .~ when requested liy that receiver. Fig. 4 shows sip alternative request points (~
s through ) where each one corresponds to a particular alternative video-stream 6 transmission (streams 402t-4071, respectively).
For example, when the exemplary fast start-up system wishes to tune to a s channel (examples are indicated by points lZi through R6), it queries the multicast 9 server (such as content server 712 of Fig. 7) in order to determine which lead-in ~o alternative stream is the first lead-in that has not started yet, and the receiver joins i ~ that alternative multicast transmission. Then, the exemplary fast start-up system lz requests that the muter switch the receiver back to the main stream multicast i3 transmission 400t just before the next RAP (e.g., frame 450t) of the main stream.
Since the alternative stream transmissions) serves as a "bridge" until the i> receiver can start receiving the next RAP of the main stream 400t, all of these i6 alternative streams (4021-408t) are shown in Fig. 4 ending at point B.
o In Fig. 4, the first frame (e.g., I-frame 450t) of the next C~4P starts at point is 1VI,. Point B on the timeline represents the end of the reception of the last frame of a4 each of the alternative streams (402t-408t) zo The switch-over from each of the alternative streams (402t-408t) back to z. the main stream 400t occurs during or around the gap between points >B and IVh in zz Fig. 4. An exaggerated and visible gap between these points is shown in Fig. 4 to z3 illustrate that there is a clear opportunity for the exemplary fast start-up system to z4 join the main stream. In reality, points B and 1VI~ may occur very nearly zs M S j -1432 tJ S 19 06 90P30857 MS 9- 9432US. PArAPP.DOC
Iee~hheyes our sos.u..szse Ariy: kasey christie concurrently and may indeed be concurrent. It is possible in some embodiments to z have a small overlap so that point B occurs shortly after point Mi.
Fig. 4 shows the alternative video-stream presentations 402p-407p that 4 correspond to the alterative video-str.~am transmissions 402p-40 7p, respectively.
Although not necessarily required, it is desirable for the alternative video-stream r, ~ presentations 402p-407p to be timed so that the last frame presented is presented immediately before the presentation of the first frame of the main stream 8 presentation 400p. Doing so enhances the smooth presentation of the video 9 content-in particular, it smoothes the presentation of the switch-over from the ~o alternative to the main stream presentations at point MZ.
a Operation of Eace~npiary Fast Start-up Svstert~
l2 Fig. 5 shows a methodological. implementation of the exemplary fast start 4 up system. This methodological implementation may be performed in software, hardware, or a combination thereof:
m At 510 of Fig. 5, the user tunes into a specific main video-stream multicast ~ transmission (e.g., 300t or 400t). This example point is designated at points R in is Fig. 3 and Rl through R6 in Fig. 4.
i9 At 512, the exemplary fast start-up system queries a multicast server (such zo as content server 712 of Fig. 7) in order to deterrraine whicliw of the alternative z~ RAP-phase-staggered lead-in alternative video streams is the first lead-in that has zz not started yet. Of course, if there is only one alternative transmission, this query z3 may be viewed simply as a request.
z4 At 514, the exemplary fast start-up system joins the alternative multicast zs transmission identified by the query. It receives and buffers this alternative Idl~1-14321lS 20 06i003C1857MS1-1432US.PAT.APP.DOC
leef~hayes wk sos.axa.szss Atry: kasey christie transmission. This occurs, for example, at designated points A in Fig. 3 and AI
z through A6 in Fig. 4.
At 516, it presents the video stream of the identified and buffered alternative transmission. This occurs, f~r example, at designated point:S in Fig. 3.
At 518, the exemplary fast start-up system switches back ~to receiving and 6 buffering the main stream qnulticast transmission ~e.g., 300t and 400t) exactly at the next RAP ~e.g., frame 3501 and ~50t) of the main stream. It may do this by 8 requesting that the muter switch the receiver back to the main stream multicast 9 transmission exactly at the next RAP of the main stream. This occurs, for to example, between or around designated points 1B and Nil in Figs. 3 and 4.
This i, may also be described as occurring "on or about" such designated points.
lz At 520, it presents the video stream of the main stream multicast. This occurs, for example, at designated point ld~z in Figs. 3 and 4.
m ~peration of Exemplary lfast Start-up lV~ulticast S~ysteen m Fig. 6 shows a methodological implementation of the exemplary fast start-,~ up multicast system, which may be embodied by a content provider 702 and/or a is content distribution system 706 of Fig. 7). This methodological implementation a9 may be performed in software, hardware, or a combination thereof.
zo At 610 of Fig. 6, the exemplary fast start-up. ~r~ulticast system concurrently z~ encodes one or more alternative video streams for transmission. The server system zz encodes each alternative stream so that the RAP of each is phase-staggered relative z3 to the other streams.
za zs v 9 -7 4320 S 21 0670030857 MS 1-Y432US.PAT APP.DOC
ke~hayes auc saraxvzss Atty: kasey chrisde Furthermore, each stream is encoded so that each ends at the same point, z which is at or near when the next RAP is available in the main video stream.
This 3 designated point, for example, is point 1V~1 in Figs. 3 and 4.
a At 612, the multicast system receives a query to which of the RAP-phase-s staggered lead-in alternative video streams is the first lead-in that has not started 6 o yet. Gf course, if there is only one alternative transmission, this query may be -, viewed simply as a request.
s At 614, it transmits the alternative multicast transmission identified by the 9 query to the receiver that requested it.
io At 616, the multicast system receives a request for the router switch the ~ ~ receiver back to the main stream multicast transmission dust before the next RAP
~z of the main stream. At 61 ~, it does so in response to such a request. This occurs, i3 for example, between or around designated points B and 11'I1 in Figs. 3 and 4.. This 1:~ may also be described as occurring "on or about" such designated points.
~s ~I Exemplary Environment m Fig. 7 illustrates an exemplary environment "700 in which the techniques, ~s systems, and other aspects described herein may he implemented (partially or :~ wholly). Exemplary environment 700 is a television entertainment system that zo facilitates distribution of mufti-media.
z ~ The environment 700 includes one or more multimedia content providers zz 702, a content distribution system 706, and one or more presentation devices z3 708(1), 708(2), ..., 70~(N) coupled to the content distribution system 706 via a za multicast-capable network 710.
M S ~ -1432 U S 22 08100;30857 MS 1-1432L1S. PAT'.APP. DOC
lee~lheyes wr sos.azoszss Atty: kasey chrstie Multimedia content provider 702 includes a content server 712 and stored z content 714, such as movies, television programs, commercials, music, and similar audio and~or video content. Content server 712 controls distribution of the stored 4 content 714 from content provider 702 to the content distribution system 706.
Additionally, content server 702 controls distribution of live content (e.g., content s that evas not previously stored, such as live feeds) andlor content: stored at other locations to the content distribution system 706.
Content distribution system 706 may be coupled to a network 720, such as an intranet or the Internet. The content distribution system 706 includes a multicast to transmitter 728, and one or more content processors 730. Multicast transmitter 728 multicasts signals across multicast-capable network 710.
iz Content distribution system 706 is representative of a headend service that 13 provides multimedia content to,multiple subscribers.
r4 Multicast-capable network 710 can include a cable television network, IgF, microwave, satellite, and,~or data network, such as the Internet, and may also ~s include wired or wireless media using any multicast format or multicast protocol.
Additionally, multicast-capable network 7I0 may be any type of network, using Is any type of network topology and any network communication protocol, and may be represented or otherwise implemented as a combination of two or more zo nets,°orks.
z~ Content processor 730 processes the content received from content provider zz 702 prior to transmitting the content across multicast-capable network 708.
A
z3 particular content processor 730 may encode, or otherwise process, the received z4 content into a format that is understood by the multiple presentation devices zs 708{1}, 708(2), ..., 708(IV) coupled to multicast-capable network 710.
M S 1-t 432tJ 5 23 06f0030857MS I-1432US.PAT APP.DOC
lee~lFeayes yn ws.aa..sasc Atty: kasey christie Presentation devices 708 may be implemented in a number of ways. For z example, a presentation device 708(1) receives content multicasted from a 3 satellite-based transmitter via a satellite dish 734. Presentation device 708( 1 ) is a also referred to as a set-top box or a satellite receiving device.
Presentation device s 708( 1 ) is coupled to a television 736( l ) for presenting the content received by the o presentation devace (e.g., audio data and video data), as well as a graphical user interface. A, particular presentation device 708 may be coupled to any number of s televisions 736 and/or similar devices that may be implemented to display or 9 otherwise render content. Similarly, any number of presentation devices 708 may o be coupled to a single television 736.
" Presentation device 708(2) is also coupled to receive content from ,2 multicast-capable network 710 and provide the received content to associated , ~ television. 736(2). Presentation device 708(N) is an example of a combination la television 738 and integrated set-top box 740. In this example, the various ,; components and functionality of the set-tap box are incorporated into the m television, rather than using tivo separate devices. The set-top box incorporated into the television may receive multicast signals via a satellite dish or wireless ,g antenna (such as dish 734) andlor via muhicast-capable network 710. In alternate 9 implementations, presentation devices 706 may receive content via the Internet or 20 ~ any other multicast medium.
2, The exemplary environment 700 also includes live or stored pay-per-view a2 (PPV) content 742, such as PPV movie content. The stored or live content is 23 typically multicast on a schedule. dVhen a device joins a PP'~l multicast channel, za the PPV content may be viewed with a presentation device 708.
M ~J 1-~ ~ 32 ~ S 2~ 067p030857 MS 1-1432USPAT APP DOC
kee~heyes uu~ sosaxosnc At9y: kesey cheistie Exemplary Presentation Device 2 ~ Fig. 8 illustrates an exemplary implementation 800 of a presentation device 3 » 708 shown as a standalone unit that connects to a television 736.
Presentation 4I~ device 708 may be implemented in any number of embodiments, including as a set-top box, a satellite receiver, a 'TV recorder with a hard disk, a game console, an 6 information appliance, a DVD player, personal video recorder, a personal ' computer, a home media center, a modem, and so forth.
Presentation device 708 includes a wireless receiving port 802, such as an 9 infrared (IR) or Bluetooth wireless port, for receiving wireless communications '° from a remote control device 804, a handheld input device 806, or any other " wireless device, such as a wireless keyboard. Handheld input device 806 may be a 'Z personal digital assistant (PD A), handheld computer, wireless phone, or the like.
13 Additionally, a wired keyboard 808 is coupled to comrriiir~icate with the 14 presentation device 708. In alternate embodiments, remote control device 804, '' handheld device 806, and/or keyboard 808 may use an RP communication link or ' S other mode of transmission to communicate with presentation device 708.
" Presentation device 708 may have a storage medium reader 809 for reading '8 content storage media, such as DVD disks. A standalone or non-standalone ''" presentation device 708 may include the storage medium reader 80~.
2° Presentation device 708 may receive one or more multicast signals 21 from one or more multicast sources, such from a multicast netw ork.
22 ~ 4 0~ .a ~ -r o 1 - t a~ .,~. ~ #«,.,..
Presenl.al.lon uevic2 10v a>.sa:1 inciuuvs haruJv'a.rC o.ildr~Or Si.omwaW for 23 providing the user with a graphical user interface by which the user can, for M S,~~ ° ~ 432 U S ZS 0610030857 MS1-1432US. PAT APP DOC
'BB~~yeS pk SOrt3Z1~9256 Atty: kasey christie example, access various network services, configure the presentation device 708, Z and perform other functions.
Presentation device 708 may be capable of communicating with other a devices via one or more corirzections including a conventional telephone link 812, s an ISI)N link 814, a cable link 816, an Ethernet link 818, a IJSL link 820, and the 6 ~i like. Presentation device 708 may use ar~y Ore or more of the various communication links 812-820 at a particular instant to communicate with any s number of other devices. The multicast signals may also be received via the 9 various communication links 812-820.
,o Presentation device 708 generates video signal{s} 820 and audio signals}
n 822, both of which are communicated to television 736. Alternatively, video and ,z audio signal may be communicated to other audic~/visual equipment, such as 13 speakers, a video mon-itor, a home theater system, an audio system, and the like.
,a Although not shown in Fig. 8, presentation device 708 rnay include one or ,; more lights or other indicators identifying the current status of the device.
,6 Additionally, the presentation device may include one or more control buttons, ~ switches, or other selectable controls for controlling operation of the device.
~s Fig. 9 illustrates selected components of presentation device 708 shown in :9 Figs. 7 and 8. Presentation deviP 708 includes a first tuner 900 and an optional zo second tune" 902. The tuners 900 and 902 are representative of one or more in-2, band tuners that tune to various frequencies or channels to receive television 2z signals, as well as an out-of band tuner or receiver or network interface card that 23 tunes to or receives the multicast communications channel over which other za content may be multicast to presentation device 708.
2sl M S 1-1432 ~J S 26 0610030857 MSt-1432US.PAT,APP,DOC
lee(~haye""' ws.aza.sxsa Atty: kasey christie The tuners 900 and 902 rnay be digital tuners, analog tuners, or any 2 combination of analog and digital components used to get digital data into the 3 client device 708.
Presentation device 708 also includes one or more processors 304 and one .
or more memory components. Examples of possible memory components include 6 a random access memor-y (RAM) 906, a disk drive 908, a mass storage cornponerst 9i0, and a non-volatile memory 912 (e.g., ROM, Flash, EPROM, EEPROM, etc.).
s Alternative implementations of presentation device 708 can include a range of processing and memory capabilities, and may include more or fewer types of o memory components than those illustrated in Fig. 9.
z i Processor(s) 904 process various instructions to control the operation of ,z presentation device 708 and to communicate with other electronic and computing 3 devices. The memory components. (e.g., RAM 906, disk drive 908, storage media 4 910, and non-volatile memory 912) store various information and/or data such as multimedia content, electronic program data, web content data, configuration i6 information for presentation device 708, and/or graphical user interface ~ information. The device may cache data into any one of these many memory 8 components.
;y An operating _system 914 an~i one or more applmation programs 916 rnay be zo stored in non-volatile mem~ry 9I2 and executed ova processor 904 to provide a 21 runtime environment. A runtime environment facilitates extensibility of z2 presentation device 708 by allowing various interfaces to be defined that, in turn, 23 allow application programs 916 to interact with presentation device 708.

MS1-1432US 27 r7670030857MS7-1432US.PAT.APPDOC
Iee~lhayes de sos.m.nzss Airy: kasey christie The application programs 91 ~ that may be implemented on the presentation z device 708 may include an electronic program guide (EPG), an email program to facilitate electronic mail, and so on.
Presentation device 7'J8 can also include other components pertaining to a s television entertainment system which are not illustrated in this example for 6 simplicity purposes. For instance, presentation device 708 car. include a user interface application and user interface lights, buttons, controls, etc. to facilitate s viewer interaction with the device.
Network interface 924 and serial and/or par. allel interface 926 allows ,o presentation device 708 to interact and communicate with other electronic and " computing devices via various communication links. Although not shown, ,z presentation device 708 may also include other types of data communication , s interfaces to communicate with other devices.
,a It may include a modem 928 or other communications device that ,; facilitates communication with other electronic and computing devices via a ,6 conventional telephone line or other communications ,mediums.
m The presentation device 708 has the ability to receive multicast digital data 18 and it may receive it using the tuners 900 or 902, th.e network interface 924, the ,9 modem 928, or other communications device.
zo Presentation device 708 also includes an ~udio/video output 930 that z, provides signals to a television or other device that processes and/or presents or zz ~ otherwise renders the audio and video data. This output rnay be called the dis la .
P Y
z3 Presentation device 708 also includes a fast start-up module 940 that za partially or wholly implements the exemplary fast start-up system. It may be a; application program or a hardware component.
51-1432 U S 28 0610030857 MS 1- 9432US.PAT'.APP. DOC
lee~hayes v~ sos.~ae.szse Atty- kasey ch~sHa Although shown separately, some of the components of presentation device z 708 may be implemented in an application specific integrated circuit {ASIC).
3 Additionally, a system bus {not shown) typically connects the various components within presentation device 708.
A system bus may be implemented as one or more of any of several types a of bus structures, including a memory bas or memory controller, a pe pheral bus, an accelerated graphics port, or a local bus using any of a variety of bus s architectures. By way of example, such architectures can include a CardBus, 9 Personal Computer Memory Card International Association (PCMCIA), m Accelerated Graphics Port {AGP~, Small Computer System Interface (SCSI), ~ Universal Serial Bus {USB), IEEE 1394, a Video Electronics Standards ~z Association (VESA) local bus, and a Peripheral Component Interconnects (PCI) 13 bus also known as a Mezzanine bus.
ml I~ Computer-Executable Instructions m An implementation of an exemplary fast start-up system may be described m in the general context of computer-executable instructions, such as program is modules, executed by one or more computers or other devices. Generally, :9 ~ program nmod~ales include ro3atines, programs, objects, components, data structures, 2o etc. that perform particular tasks or implement particular abstract data types.
z~ Typically, the functionality of the program modules may be combined or zz distributed as desired in various embodiments.

MS1-1432US 29 06J0030857MS1-P432US.PAT.APPDOC
IeeQlhayes on~ sai.ua.s2~ Atty: kasey chrisrie ~! Computer readable Media z An implementation of an exemplary fast start-up system may be stored an 3 or transmitted across some form of computer readable media. Computer readable 4 media may be any available media that may be accessed by a computer. 13y way s of example, and not limitation, computer readable media may comprise "computer 6 storage media" and "communications media."
"Computer storage media" include volatile and non-volatile, removable and g non-removable media implemented in any method ar technology for storage of 9 information such as computer readable instructions, data structures, program '° modules, or other data. Computer storage media includes, but is not limited to, " RAM, ROM, EEpROM, flash memory or other memory technology, CD-ROM, 'z digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic '3 tape, magnetic disk storage or other magnetic storage devices, or any other ''~ medium which may be used to store the desired information and which may be is accessed by a computer.
'S "Communication media" typically embodies computer readable '' instructions, data structures, program modules, or other data in a modulated data '8 signal, such as carrier wave or other transport mechanism. Communication media '~ also includes any information delivery media.
2o The term "modulated data signal" means a signal that has one or more of its z' characteristics set or changed in such a manner as to encode information in the zz jlgnal. tray wa y' of v,Xaix pier, and r'xot llmiiatlon, i vas Ta'i'lniCatiC3a media lnCiLI'.~eS
23 wired media such as a wired network or direct-wired connection, and wireless za M S 1-1432US 30 06>003'OB57MSi-7432US.PATJIPP.OOC
IeetElhayes a< sos.sxa.szs' Atty: kasey ch~slie 1 media such as acoustic, RF, infrared, and other u-~ireless media.
Combinations of z any of the above are also included within the scope of computer readable media.
Coe~c~usion a Although the invention has been described in language specific to structural 6 features ar~cL'or methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific features or s steps described. Rather, the specific features and steps are disclosed as preferred 9 forms of implementing the claimed invention.
to l4 I

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M S ~ -1432 U S 31 0610030857 MS 9-1432US. PAT.APP.OOC
Atty- kasey chri5tie

Claims (7)

1. A computer-readable medium having computer-executable instructions that, when executed by a computer, perform a method comprising:
selecting a lead-in video stream, where the lead-in stream corresponds to a particular main video-stream transmission;
receiving the selected lead-in video-stream transmission;
presenting content of the selected lead-in video stream transmission;
switching reception from the lead-in to the main video-stream transmission;
switching presentation from the content of the lead-in to the content of the main video-stream transmission.

2. A medium as recited in claim 1, wherein the selected lead-in video stream of the selecting is chosen from one of multiple lead-in video streams.

3. A medium as recited in claim 1, wherein the switching occurs on or about the occurrence a random-access point (RAP) transmitted in the main video-stream transmission.

4. A medium as recited in claim 1, wherein the switching occurs dust before the occurrence a random-access point (RAP) transmitted in the main video-stream transmission.

5. A medium as recited in claim 1 further comprising querying a video-stream provider asking the provider to identify which one of the multiple lead-in video-stream transmissions is the first transmission with an available RAP, wherein the identified lead-in transmission is the one selected.

6. A medium as recited in claim 1, wherein the multiple lead-in video-stream transmissions are scheduled for transmission during transmission of one group-of pictures (GOP) of the main video-stream transmission, wherein a GOP
has only one RAP.

7. A medium as recited in claim 1, wherein the RAP of each of the multiple lead-in video-stream transmissions are scheduled for phase-staggered transmission relative to each other.
7. A medium as recited in claim 1, wherein each of the multiple lead-in video-stream transmissions are encoded using a lower bitrate than that used by the main video-stream transmission.
9. A medium as recited in claim 1, wherein the video-stream transmissions are multicast.
10. A computing device comprising:
a video-stream presentation device;
a medium as recited in claim 1.

11. A computer-readable medium having computer-executable instructions that, when executed by a computer, perform a method comprising:
choosing a particular main video-stream transmission for reception and presentation;
before the transmission of the next random-access point (RAP) transmitted in the main video-stream transmission, temporarily receiving a lead-in video stream that corresponds to the particular main video-stream transmission;
switching reception from the lead-in to the main video-stream transmission.
12. A medium as recited in claim 11 further comprising presenting content of the lead-in video stream transmission;
after switching reception to the main video-stream, presenting the content of the main video-stream transmission.
13. A medium as recited in claim 11, wherein the switching is performed on or about the transmission of a RAP in the main video-stream transmission.
14. A medium as recited in claim 11, wherein the switching is performed-on or about the transmission of the next RAP to occur during the main video-stream transmission.

15. A medium as recited in claim 11, wherein the lead-in video-stream transmission is scheduled for transmission during transmission of one group-of-pictures (GOP) of the main video-stream transmission, wherein a GOP has only one RAP.
16. A medium as recited in claim 11, wherein each of the multiple lead-in video-stream transmissions are encoded using a lower bitrate than that used by the main video-stream transmission.
17. A medium as recited in claim 11, wherein the video-stream transmissions are multicast.
18. A computing device comprising:
a video-stream presentation device;
a medium as recited in claim 11.

19. A medium as recited in claim 11 further comprising:
selecting one of multiple lead-in video-stream transmissions for reception, where each lead-in stream corresponds to a particular main video-stream transmission, wherein the one lead-in transmission selected is the lead-in transmission that is temporarily received;
presenting content of the selected lead-in video stream transmission;
switching reception from the lead-in to the main video-stream transmission and doing so on or about the occurrence a random-access point (RAP) transmitted in the main video-stream transmission;
switching presentation from the content of the lead-in to the content of the main video-stream transmission;
20. A medium as recited in claim 19 further comprising querying a video-stream provider asking the provider to identify which one of the multiple lead-in video-stream transmissions is the first transmission with an available RAP, wherein the identified lead-in transmission is the one selected.
21. A medium as recited in claim 19, wherein the multiple lead-in video-stream transmissions are scheduled for transmission daring transmission of one group-of pictures (GOP) of the main video-stream transmission, wherein a GOP
has only one RAP.

22. A medium as recited in claim 19, wherein the RAP of each of the multiple lead-in video-stream transmissions are scheduled for phase-staggered transmission relative to each other.
23. A medium as recited in claim 19, wherein each of the multiple lead-in video-stream transmissions are encoded using a lower bitrate than that used by the main video-stream transmission.
24. A method for fast start-up presentation, the method comprising:
selecting one of multiple lead-in video-stream transmissions for reception, where each lead-in stream corresponds to a particular main video-stream transmission;
receiving the selected lead-in video-stream transmission;
presenting content of the selected lead-in video stream transmission;
switching reception from the lead-in to the main video-stream transmission and doing so upon the occurrence a random-access point (RAP) transmitted in the main video-stream transmission;
switching presentation from the content of the lead-in to the content of the main video-stream transmission.
25. A method as recited in claim 24 further comprising querying a video-stream provider asking the provider to identify which one of the multiple lead-in video-stream transmissions is the first transmission with an available RAP, wherein the identified lead-in transmission is the one selected.

26. A method as recited in claim 24, wherein the multiple lead-in video-stream transmissions are scheduled for transmission during transmission of one group-of pictures (GOP) of the main video-stream transmission, wherein a GOP
has only one RAP.
27. A method as recited in claim 24, wherein the RAP of each of the multiple lead-in video-stream transmissions are scheduled for phase-staggered transmission relative to each other.
28. A method as recited in claim 24, wherein each of the multiple lead-in video-stream transmissions are encoded using a lower bitrate than that used by the main video-stream transmission.
29. A method as recited in claim 24, wherein the video-stream transmissions are multicast.
30. A computer comprising one or more computer-readable media having computer-executable instructions that, when executed by the computer, perform the method as recited in claim 24.

31. A computer-readable medium having computer-executable instructions that, when executed by a computer, perform a method comprising:
preparing multiple video-streams based upon the same original video content for an overlapping transmission schedule so that the random access point (RAP) of each is phase-staggered;
transmitting one of more of the multiple video-streams over a communications network in accordance with the overlapping transmission schedule.

32. A medium as recited in claim 31, wherein the transmission of the group-of-pictures (GOP) of each of the multiple streams ends on or about the same point in the transmission schedule.

33. A medium as recited in claim 31, wherein the multiple video-streams comprise a main stream and a lead-in stream.

34. A medium as recited in claim 31, wherein one or more of the video-streams are encoded using a lower bitrate than one or more of the other streams.

35. A computing device comprising:
a transmitting device for transmitting one or more of the multiple video-streams;
a medium as recited in claim 31.