WO2010015882A1

WO2010015882A1 - Fast channel zapping

Info

Publication number: WO2010015882A1
Application number: PCT/IB2008/053180
Authority: WO
Inventors: David Fink; Sara Novogrodsky; Yair Mirsky; Kevin Murray
Original assignee: Nds Limited
Priority date: 2008-08-07
Filing date: 2008-08-07
Publication date: 2010-02-11

Abstract

A method and system is described for tuning a set top box to a carrier frequency, the carrier frequency carrying a transport stream, acquiring a subset of transport stream associated metadata, the subset of transport stream associated metadata including a plurality of pointers to a plurality of elementary streams, the plurality of elementary streams including data and metadata associated with a desired content item, acquiring the plurality of elementary streams indicated in the subset of transport stream associated metadata, the plurality of elementary streams including at least a first stream including encrypted video frames, the encrypted video frames including at least one frame which includes an encrypted access point, and a second stream including an entitlement control word (ECM) stream, caching the encrypted video frames acquired from the first stream, acquiring an ECM from the second stream, the acquired ECM being associated with the cached acquired encrypted video frames, deriving a control word (CW) from the acquired ECM, decrypting the cached acquired encrypted video frames according to the CW, locating the at least one decrypted access point in the first stream, decrypting encrypted video frames included in the cached first stream, decoding the decrypted video frames from the at least one decrypted access point, and displaying the decoded decrypted video frames included in the first stream, beginning at the located at least one decrypted access point, wherein the decrypting, decoding and displaying is performed at better than real-time. Related systems and methods are also described.

Description

FAST CHANNEL ZAPPING

BACKGROUND OF THE INVENTION

Changing channels, in modern television systems, is referred to as "channel zapping". The time required for a set top box to tune to a new channel; begin decrypting an encrypted broadcast on the new channel; decompress (that is to say, using the correct term of the art: "decode") decrypted video on the new channel; and actually begin displaying decompressed (decoded) decrypted video on the new channel is, accordingly, referred to as zapping time. The following references, listed by publication number, are believed to reflect the current state of the art:

US 5,933,192, to Crosby, et al; US 6,118,498, to Reitmeier; US 6,157,673 to Cuccia; US 6,334,217, to Kim;

US 6,519,011, to Shendar; US 6,714,264, to Kempisty; US 2004/0187161, of Cao; US 2005/0163163, of Kim et al.; US 2005/0172314, of Krakora et al.;

US 2006/0083263, of Jagadeesan et al.; US 2007/0220557, of Lee et al.; US 2007/0234386, of Kim; WO 2006/044547 of OpenTV, Inc.; WO 2006/121801 of Thomson Licensing;

JP 2001-016513 of Sharp Corp.; JP 2005-080142 of Sanyo Electric Co.; and JP 2007-116213 of Sharp Corp. SUMMARY OF THE INVENTION

There is thus provided in accordance with an embodiment of the present invention a method including tuning a set top box to a carrier frequency, the carrier frequency carrying a transport stream, acquiring a subset of transport stream associated metadata, the subset of transport stream associated metadata including a plurality of pointers to a plurality of elementary streams, the plurality of elementary streams including data and metadata associated with a desired content item, acquiring the plurality of elementary streams indicated in the subset of transport stream associated metadata, the plurality of elementary streams including at least a first stream including encrypted video frames, the encrypted video frames including at least one frame which includes an encrypted access point, and a second stream including an entitlement control word (ECM) stream, caching the encrypted video frames acquired from the first stream, acquiring an ECM from the second stream, the acquired ECM being associated with the cached acquired encrypted video frames, deriving a control word (CW) from the acquired ECM, decrypting the cached acquired encrypted video frames according to the CW, locating the at least one decrypted access point in the first stream, decrypting encrypted video frames included in the cached first stream, decoding the decrypted video frames from the at least one decrypted access point, and displaying the decoded decrypted video frames included in the first stream, beginning at the located at least one decrypted access point, wherein the decrypting, decoding and displaying is performed at better than real-time.

Further in accordance with an embodiment of the present invention the displaying includes at least one of displaying all decrypted decoded frames until the decoding of the video has caught up with the real time broadcast, displaying only some of the decrypted decoded frames until the decoding of the video has caught up with the real time broadcast, displaying only a single decrypted decoded I-frame until the decoding of the video has caught up with the real time broadcast, and not displaying any video until the decoding of the video has caught up with the real time broadcast.

Still further in accordance with an embodiment of the present invention the access point includes a recovery point. Additionally in accordance with an embodiment of the present invention the set top box includes a personal video recorder.

Moreover in accordance with an embodiment of the present invention the displaying includes displaying substantially immediately after decoding the decrypted first stream.

Further in accordance with an embodiment of the present invention the decrypting, decoding and displaying is performed at better than real-time until the displaying catches-up to a real-time display.

Still further in accordance with an embodiment of the present invention the decrypting, decoding and displaying includes not decoding and not displaying selected decrypted frames.

Additionally in accordance with an embodiment of the present invention the selected decrypted frames include at least one frame that can be used as a reference for decoding at least one other frame. Moreover in accordance with an embodiment of the present invention the selected decrypted frames include at least one of an I-frame and a P- frame.

Further in accordance with an embodiment of the present invention the selected decrypted frames include non-advertisement associated frames. Still further in accordance with an embodiment of the present invention the at least one decrypted access point includes one of an intra-coded frame (I-frame), and an Instantaneous Decoding Refresh frame (IDR-frame).

Additionally in accordance with an embodiment of the present invention the acquiring the plurality of elementary streams indicated in the subset of transport stream associated metadata includes acquiring a program association table (PAT) from the transport stream, based on information in the PAT, acquiring a program map table (PMT), acquiring the plurality of elementary streams indicated in the PMT.

Moreover in accordance with an embodiment of the present invention the acquiring the plurality of elementary streams indicated in the subset of transport stream associated metadata includes acquiring out-of-band data, and the acquiring the plurality of elementary streams includes acquiring the plurality of elementary streams indicated in the acquired out-of-band data .

Further in accordance with an embodiment of the present invention the acquired out-of-band data includes data in a proprietary format. Still further in accordance with an embodiment of the present invention the acquired out-of-band data includes non-DVB format data.

Additionally in accordance with an embodiment of the present invention the decrypting includes partial decrypting.

Moreover in accordance with an embodiment of the present invention the decoding includes partial decoding.

There is also provided in accordance with a another embodiment of the present invention a method including tuning a set top box to a carrier frequency, the carrier frequency carrying a transport stream, acquiring a program association table (PAT) from the transport stream, based on information in the PAT, acquiring a program map table (PMT), acquiring elementary streams indicated in the PMT, the elementary streams including at least a stream including encrypted video frames, the encrypted video frames including at least one frame which includes an encrypted access point, and an entitlement control word (ECM) stream, caching the acquired encrypted video frames, acquiring an ECM from the ECM stream, deriving a control word (CW) from the ECM, decrypting the cached acquired encrypted video frames according to the CW, locating the at least one decrypted access point in the cached video stream, decoding at least one decrypted video frame from the at least one decrypted access point, and displaying the at least one decoded decrypted video frame beginning at the located at least one decrypted access point, wherein the decrypting and decoding is performed at better than real-time.

There is also provided in accordance with still another embodiment of the present invention a system including a tuner included in a set top box which tunes the set top box to a carrier frequency, the carrier frequency carrying a transport stream, a subset of transport stream associated metadata acquired by the set top box, the subset of transport stream associated metadata including a plurality of pointers to a plurality of elementary streams, the plurality of elementary streams including data and metadata associated with a desired content item, the plurality of elementary streams indicated in the subset of transport stream associated metadata acquired by the set top box, the plurality of elementary streams including at least a first stream including encrypted video frames, the encrypted video frames including at least one frame which includes an encrypted access point, and a second stream including an entitlement control word (ECM) stream, a cache included in the set top box that caches the encrypted video frames acquired from the first stream, an ECM from the second stream which is acquired by the set top box, the acquired ECM being associated with the cached acquired encrypted video frames, a control word (CW) derived by the set top box from the acquired ECM, a decryptor which decrypts the cached acquired encrypted video frames according to the CW, a locator which locates the at least one decrypted access point in the first stream, a second decryptor which decrypts encrypted video frames included in the cached first stream, a video decoder which decodes the decrypted video frames from the at least one decrypted access point, and a display outputting unit which displays the decoded decrypted video frames included in the first stream, beginning at the located at least one decrypted access point, wherein the decryptor, the second decryptor, the video decoder and the display outputting unit perform at better than real-time. There is also provided in accordance with still another embodiment of the present invention a system including a tuner included in a set top box which tunes the set top box, the carrier frequency carrying a transport stream, a program association table (PAT) which is acquired from the transport stream by the set top box, a program map table (PMT) which is acquired by the set top box based on information in the PAT, acquiring, elementary streams indicated in the PMT which are acquired by the set top box, the elementary streams including at least a stream including encrypted video frames, the encrypted video frames including at least one frame which includes an encrypted access point, and an entitlement control word (ECM) stream, a cache which caches the acquired encrypted video frames, an ECM acquired by the set top box from the ECM stream, a control word (CW) derived by the set top box from the ECM, a decryptor which decrypts the cached acquired encrypted video frames according to the CW, a locator which locates the at least one decrypted access point in the cached video stream, a video decoder which decodes at least one decrypted video frame from the at least one decrypted access point, and a display outputting unit which displays the at least one decoded decrypted video frame beginning at the located at least one decrypted access point, wherein the decryptor and the video decoder perform at better than real-time.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: Fig. 1 is a simplified partly pictorial partly block diagram illustration of a system for fast channel zapping constructed and operative in accordance with an embodiment of the present invention;

Fig. 2 is a simplified block diagram illustration of the operation of the system of Fig. 1 in an MPEG environment; Fig. 3 is a simplified flowchart of the method of operation of the system of Fig. 2;

Fig. 4 is a graphical representation depicting a plot of time from PID filter set up until the first I-frame is acquired vs. time until the decoding of the video has caught up with the real time broadcast, with the system of Fig. 1 utilized, and in the absence of the system of Fig. 1;

Fig. 5 is a graphical representation similar to Fig. 4, utilizing a less conservative estimate of burst time; and

Fig. 6 is a simplified flowchart of methods of operation of the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT Reference is now made to Fig. 1, which is a simplified partly pictorial partly block diagram illustration of a system for fast channel zapping constructed and operative in accordance with an embodiment of the present invention. The system of Fig. 1 comprises a video transport stream 10, the video transport stream comprising transport stream associated metadata 15 and elementary streams comprising a video stream 20 and an entitlement control word (ECM) stream 30.

The system of Fig. 1 further comprises a set top box (STB) 40, the STB 40 comprising a cache 50, a decryptor 60 and a decoder 70. It is appreciated that the STB 40 comprises standard hardware components and software components, as is known in the art. The STB 40 may comprise a personal video recorder (PVR), also known in the art as a digital video recorder (DVR).

The operation of the system of Fig. 1 is now described. A video headend 80 broadcasts the transport stream 10 comprising the video stream 20, the ECM stream, and the transport stream associated metadata 15. The STB 40 acquires the transport stream 10. The transport stream associated metadata 15 comprises pointers to the elementary streams. When the STB 40 tunes to a particular content item, particular transport stream associated metadata 15 directs the STB 40 to locate particular packets in the video transport stream 10, the particular packets being packets comprising encrypted video frames 21a, 21b, ..., 2 Ix comprised in the video stream 20 for the particular content item and packets comprising ECMs 31a, 31b, ..., 3 Ix in an associated ECM stream 30. Those skilled in the art will appreciate that the ECMs comprising the associated ECM elementary stream 30 comprise ECMs required for decryption of the encrypted video frames 21a, 21b, ..., 21x.

It is appreciated that the decryption of the encrypted video frames 21a, 21b, ..., 21x may comprise partial decryption. For example and without limiting the generality of the foregoing, some video standards comprise plain text indicators as to where encrypted access points are located in the transport stream 10. In such a case, decryption would begin at the located access point, and possibly only some of the following frames would be decrypted. Those skilled in the art will appreciate that the plain text indicators can be used to indicate the access point or a recovery point, in standards which support recovery points.

The encrypted video frames 21a, 21b, ..., 21x are stored in the cache 50. A control word (CW) 90 is derived from one ECM 31b, being an ECM associated with the cached acquired encrypted video frames 21a, 21b, ..., 2 Ix. The control word 90 is sent to the decryptor 60 and is used to decrypt the cached acquired encrypted video frames 21a, 21b, ..., 2 Ix. The decrypted video frames 121a, 121b, ..., 121x are sent to the decoder 70. Those skilled in the art will appreciate that the term decoder is used in its conventional use in the art to refer to a video decompressor. The decoder 70 decodes the decrypted video frames 121a, 121b, ..., 121x beginning at an access point. The decoded decrypted video frames 221a, 221b, ..., 221x are sent to a video display 230 for displaying. It is appreciated that in the operation of system of Fig. 1, as described above, the decrypting, the decoding and the displaying are all performed at speeds better than real-time. It is anticipated that by performing the decrypting, the decoding and the displaying at speeds better than real-time, the displaying of the video will eventually catch up with the real time broadcast. Alternatively, any one of the decrypting and the decoding may occur at better than real-time, while the displaying may occur at real-time. It is appreciated that the decoding of the decrypted video frames 121a, 121b, ..., 121x may comprise partial decoding. For example and without limiting the generality of the foregoing, in some embodiments of the present invention, some or all decrypted bi-directional picture or equivalent frames may not be decoded, as discussed below. Those skilled in the art will appreciate that the access point mentioned above comprises any frame after which the video stream can be decoded without reference to other frames. Typically, access points comprise intra-coded frames (I-frames), Instantaneous Decoding Refresh frames (IDR- frames), or equivalent frames. In standards which support recovery points, a recovery point may also comprise an access point.

Additionally, those skilled in the art will appreciate that the access point mentioned above may also comprise a frame and a count where the video stream can be decoded and displayed without reference to other frames after "count" frames beyond the access point frame. The frame from which decoding can begin may be of any type (for example and without limiting the generality of the foregoing, an MPEG-2 I-frame, or a bi-directionally predicted frame in H.264 comprising a progressive I-slice). Of the frames in the "count" that are received after the access point, and including the access point, some frames may be suitable for displaying as they have been completely decoded whereas other frames may not be suitable for displaying as some of the information required for decoding such frames is based on frames that have not been received. Those skilled in the art will further appreciate that in order to achieve the decrypting, the decoding and the displaying being performed at speeds better than real-time, it may be necessary to not display all decrypted and decoded frames. One method to perform the decrypting, the decoding and the displaying at speeds better than real-time comprises not displaying every decrypted and decoded bi-directional picture frames (B-frames), or the equivalent frames that are not required as input to decoding other frames. Alternatively, while B-frames may be decrypted, the decrypted B-frames may not be decoded. In another embodiment of the present invention, the B-frames which are not decoded comprise B-frames which are associated with content items and not with advertisements. Alternatively, the B-frames which are not decoded may comprise B-frames which are associated with advertisements and not with content items. In another embodiment of this invention, a first I-frame after the access point may be displayed, and no change of display may occur until the decoding of the video has caught up with the real time broadcast. The implementation of this invention may result in a video stream being displayed slightly behind or slightly ahead of the normal expected display time, as encoded in the video. The stream can be adjusted either to the correct display time using the better-than real time mechanisms described above, or, alternatively, using the well-known technique of displaying all of the frames, at a slightly faster than real-time rate.

Those skilled in the art will appreciate that some video encoding systems support self-decodable frames (e.g. I-frames) that are not access points, i.e. such frames do not allow the decoding of all the following frames up until the next access point. For example and without limiting the generality of the foregoing, one I-frame followed by a second intra-coded frame I-frame would comprise an I-frame which is not an access point. A somewhat more complex example of an I-frame which is not an access point is where the I-frame is used for decoding some of the images following the I-frame, but not many, and it is not sufficient to enter the video stream. Such a case might be a "pop" video which has a sequence of fast cuts between scenes Sl, S2 and back to Sl . Assume that the first portion of S 1 starts with an I-frame from which all the frames in both portions of Sl are predicted, and S2 starts with an I-frame from which all the frames in Sl are predicted. The I-frame beginning Sl is an access point, but the I-frame beginning S2 is not, since the "back to Sl" stream requires the I-frame that occurred at the start of the first Sl segment.

Such frames that occurred before the access point may be ignored, while those after the access point would be handled as described above. Those skilled in the art will also appreciate that video encoding is sometimes performed with a "long GOP" structure, which means that there is a large gap between access points. Where such streams are processed by the present invention, it is possible that an access point has not been cached by the time the control word is available. In such cases, it may be desirable to decode and display any such I-frames received in advance of the access point.

The following implementations of the displaying are possible, in light of the above discussion: all frames are displayed until the decoding of the video has caught up with the real time broadcast; only some frames are displayed until the decoding of the video has caught up with the real time broadcast; only a single I-frame is displayed until the decoding of the video has caught up with the real time broadcast; and no video is displayed until the decoding of the video has caught up with the real time broadcast. It is appreciated that in some video systems, combinations of the above implementations may be implemented.

Reference is now made to Figs. 2 and 3. Fig. 2 is a simplified block diagram illustration of the operation of the system of Fig. 1 in an MPEG environment, and Fig. 3 is a simplified flowchart of the method of operation of the system of Fig. 2. The method and system depicted in Figs. 2 and 3 are intended to illustrate one embodiment of the present invention. The method and system depicted in Figs. 2 and 3 are by way of example only, and do not limit the generality of the foregoing description of Fig. 1. Specifically, in a non-MPEG environment, using, for example, a proprietary system of video distribution, the general description of Fig. 1 applies, without recourse to the system and method depicted in Figs. 2 and 3.

Turning specifically to Fig. 2, the STB 40 acquires the stream of metadata 15. The stream of metadata 15 comprises a Program Association Table (PAT) 310 and a Program Map Table (PMT) 320. Additionally, the STB 40 acquires the video stream 20 and the ECM stream 30. Having acquired the PAT 310, the STB 40 is able to locate the PMT 320 in the metadata stream and acquire the PMT 320. Having acquired the PMT 320, the STB 40 is able to locate the particular content item desired and to begin acquiring elementary streams comprising the video elementary stream 20 and the ECM stream 30. The STB 40 acquires the ECM 31b from the ECM stream, the ECM 31b being associated with the desired particular content item. The ECM 31b is utilized by the STB 40 in order to derive the control word 90.

The STB 40 also acquires video frames 21a, 21b, ..., 21x from the elementary video stream 20. The STB 40 caches video frames 21a, 21b, ..., 21x in the cache 50. The STB 40 sends the control word 90 and the cached video frames 21a, 21b, ..., 21x to the decryptor 60. Those skilled in the art will appreciate that, as noted above, the control word 90 is derived from the ECM 31b. Deriving the control word 90 from the ECM 31b is a time-consuming process, involving cryptographic calculations. The decryptor 60 produces decrypted compressed video frames, as described above, with reference to Fig. 1. The STB 40 determines which of the decrypted compressed video frames is the first decrypted compressed video frames comprising an access point. Beginning with the first decrypted compressed video frames comprising one of an access point and a recovery point, the decrypted compressed video frames are sent to the decoder 70, which decodes the decrypted compressed video frames, thereby producing decrypted decoded video frames, as described above, with reference to Fig. 1. As described above, with reference to Fig. 1 , the decrypted decoded video frames can be sent to the display 230 for displaying.

The method of Fig. 3 is believed to be self-explanatory in light of the above discussion of Fig. 2. Reference is now made to Fig. 4, which is a graphical representation depicting a plot of time from PID filter set up until the first I-frame is acquired vs. time until the decoding of the video has caught up with the real time broadcast, with the system of Fig. 1 utilized, and in the absence of the system of Fig. 1. The abscissa of Fig. 4 is denoted as "I-frame time". I-frame time is defined as a time from PID filter set up until the first I-frame is acquired. The ordinate of Fig. 4 is denoted as "Decode time" which is defined as the time from acquisition of the video frames until decoding can start. Note that the discussion of Fig. 4, and Fig. 5, below, utilizes MPEG-2 terminology, for example and without limiting the generality of the foregoing, describing the access point as an I-frame. It is appreciated that the discussion of Fig. 4 and Fig. 5 can be adapted appropriately for other video standards, such as H.264 and VC-I .

In order to understand Fig. 4, the following additional parameters are defined:

Burst time - a time required for the decoder 70 (Fig. 1) to processed cached content and catch up to a live broadcast. Burst time also includes decoder and stream specific overhead, such as, and not limited to, time required for hardware setup, and software overhead, as is known in the art. In Fig. 4, burst time is assumed to be 50 milliseconds.

Control Word (CW) time - a time required to acquire an ECM 31a, 31b, ..., 31x (Fig. 1) and produce a control word 90 (Fig. 1) from the ECM 31a, 31b, ..., 31x (Fig. 1). In Fig. 4, CW time is assumed to be 300 milliseconds. Those skilled in the art will appreciate that CW time in a typical STB varies from about 200 - 400 milliseconds.

GOP time - a time between starts of groups of pictures (GOPs). In Fig. 4, GOP time is assumed to be 500 milliseconds, since the GOP time for DVB is 500 milliseconds. As noted above, Fig. 4, and Fig. 5 below, are described in MPEG-2 terminology. Accordingly, those skilled in the art will appreciate that the GOP discussed herein is a closed GOP, that is, a GOP beginning with an access point. As described above, the present invention is operable in systems which allow either a closed GOP or an open GOP. Fig. 4 depicts two lines: a first (solid) line with I-frame caching (that is to say, implementing an embodiment of the present invention). Specifically, with caching

I-frames, as described above. If I-frame time is less than CW time + Burst time, then I-frame time = CW time + Burst time. Otherwise, if I-frame time is greater than CW time + Burst time, the I-frame time = I-frame time; and a second (dashed) line with no I-frame caching (that is to say, not implementing an embodiment of the present invention). Specifically, If I- frame time is less than CW time, then I-frame time = I-frame time + GOP time.

Otherwise, if I-frame time is greater than CW time the I-frame time = I-frame time.

It is appreciated that although Figs. 4 and 5 (below) and the descriptions thereof refer to I-frames, as explained above, any appropriate access point may be utilized.

For the convenience of the reader, the values plotted in Fig. 4 are presented in Table 1 , below.

Table 1 (times in milliseconds)

Those skilled in the art will appreciate that I-frame time is statistically evenly distributed over the indicated I-frame time between 0 to GOP time. That is to say, someone who tunes to the transport stream 10 (Fig. 1) is as likely to have any one I-frame time between 0 to GOP time as any other I-frame time between 0 to GOP time.

It is clear from Fig. 4 and Table 1 that the present invention that for I-frame times faster than 300 milliseconds (i.e. less than GOP time), where burst time is 50 milliseconds, embodiments of the present invention are advantageous over prior art systems in use.

Reference is now made to Fig. 5, which is a graphical representation similar to Fig. 4, using a less conservative estimate of burst time. As noted above, burst time is the time required for the decoder 70 (Fig. 1) to processed cached content and catch up to a live broadcast. In Fig. 5, burst time is set to 5 milliseconds.

For the convenience of the reader, the values plotted in Fig. 5 are presented in Table 2, below.

Table 2 (times in milliseconds)

It is clear from Fig. 5 and Table 2 that the present invention that for I-frame times faster than 300 milliseconds (i.e. less than GOP time), where burst time is 5 milliseconds, embodiments of the present invention are advantageous over prior art systems in use.

Reference is now made to Fig. 6, which is a simplified flowchart of methods of operation of the present invention. The method of Fig. 6 is believed to be self-explanatory in light of the above discussion. It is appreciated that software components of the present invention may, if desired, be implemented in ROM (read only memory) form. The software components may, generally, be implemented in hardware, if desired, using conventional techniques. It is further appreciated that the software components may be instantiated, for example: as a computer program product; on a tangible medium; or as a signal interpretable by an appropriate computer.

It is appreciated that various features of the invention which are, for clarity, described in the contexts of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment may also be provided separately or in any suitable subcombination.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the invention is defined by the appended claims and equivalents thereof:

Claims

What is claimed is:CLAIMS

1. A method comprising: tuning a set top box to a carrier frequency, the carrier frequency carrying a transport stream; acquiring a subset of transport stream associated metadata, the subset of transport stream associated metadata comprising a plurality of pointers to a plurality of elementary streams, the plurality of elementary streams comprising data and metadata associated with a desired content item; acquiring the plurality of elementary streams indicated in the subset of transport stream associated metadata, the plurality of elementary streams including at least: a first stream comprising encrypted video frames, the encrypted video frames comprising at least one frame which comprises an encrypted access point; and a second stream comprising an entitlement control word (ECM) stream; caching the encrypted video frames acquired from the first stream; acquiring an ECM from the second stream, the acquired ECM being associated with the cached acquired encrypted video frames; deriving a control word (CW) from the acquired ECM; decrypting the cached acquired encrypted video frames according to the CW; locating the at least one decrypted access point in the first stream; decrypting encrypted video frames comprised in the cached first stream; decoding the decrypted video frames from the at least one decrypted access point; and displaying the decoded decrypted video frames comprised in the first stream, beginning at the located at least one decrypted access point, wherein said decrypting, decoding and displaying is performed at better than real-time.

2. The method according to claim 1 and wherein the displaying comprises at least one of: displaying all decrypted decoded frames until the decoding of the video has caught up with the real time broadcast; displaying only some of the decrypted decoded frames until the decoding of the video has caught up with the real time broadcast; displaying only a single decrypted decoded I-frame until the decoding of the video has caught up with the real time broadcast; and not displaying any video until the decoding of the video has caught up with the real time broadcast.

3. The method according to either claim 1 or claim 2 and wherein the access point comprises a recovery point.

4. The method according to any of claims 1 - 3 and wherein the set top box comprises a personal video recorder.

5. The method according to any of claims 1 - 4 and wherein the displaying comprises displaying substantially immediately after decoding the decrypted first stream.

6. The method according to claim 5 and wherein the decrypting, decoding and displaying is performed at better than real-time until the displaying catches-up to a real-time display.

7. The method according to claim 6 and wherein the decrypting, decoding and displaying comprises not decoding and not displaying selected decrypted frames.

8. The method according to claim 7 and wherein the selected decrypted frames comprise at least one frame that can be used as a reference for decoding at least one other frame.

9. The method according to claim 7 and wherein the selected decrypted frames comprise at least one of an I-frame and a P-frame.

10. The method according to either of claim 7 or claim 8 and wherein the selected decrypted frames comprise non-advertisement associated frames.

11. The method according to any of claims 1 - 10 and wherein the at least one decrypted access point comprises one of: an intra-coded frame (I-frame); and an Instantaneous Decoding Refresh frame (IDR-frame).

12. The method according to any of claims 1 - 1 1 and wherein the acquiring the plurality of elementary streams indicated in the subset of transport stream associated metadata comprises: acquiring a program association table (PAT) from the transport stream; based on information in the PAT, acquiring a program map table

(PMT); acquiring the plurality of elementary streams indicated in the PMT.

13. The method according to any of claims 1 - 10 and wherein the acquiring the plurality of elementary streams indicated in the subset of transport stream associated metadata comprises acquiring out-of-band data; and the acquiring the plurality of elementary streams comprises acquiring the plurality of elementary streams indicated in the acquired out-of-band data .

14. The method according to claim 13 and wherein the acquired out-of- band data comprises data in a proprietary format.

15. The method according to claim 13 and wherein the acquired out-of- band data comprises non-DVB format data.

16. The method according to any of claims 1 - 15 and wherein the decrypting comprises partial decrypting.

17. The method according to any of claims 1 - 16 and wherein the decoding comprises partial decoding.

18. A method comprising: tuning a set top box to a carrier frequency, the carrier frequency carrying a transport stream; acquiring a program association table (PAT) from the transport stream; based on information in the PAT, acquiring a program map table (PMT); acquiring elementary streams indicated in the PMT, the elementary streams including at least: a stream comprising encrypted video frames, the encrypted video frames comprising at least one frame which comprises an encrypted access point; and an entitlement control word (ECM) stream; caching the acquired encrypted video frames; acquiring an ECM from the ECM stream; deriving a control word (CW) from the ECM; decrypting the cached acquired encrypted video frames according to the CW; locating the at least one decrypted access point in the cached video stream; decoding at least one decrypted video frame from the at least one decrypted access point; and displaying the at least one decoded decrypted video frame beginning at the located at least one decrypted access point, wherein said decrypting and decoding is performed at better than real-time.

19. A system comprising: a tuner comprised in a set top box which tunes the set top box to a carrier frequency, the carrier frequency carrying a transport stream; a subset of transport stream associated metadata acquired by the set top box, the subset of transport stream associated metadata comprising a plurality of pointers to a plurality of elementary streams, the plurality of elementary streams comprising data and metadata associated with a desired content item; the plurality of elementary streams indicated in the subset of transport stream associated metadata acquired by the set top box, the plurality of elementary streams including at least: a first stream comprising encrypted video frames, the encrypted video frames comprising at least one frame which comprises an encrypted access point; and a second stream comprising an entitlement control word (ECM) stream; a cache comprised in the set top box that caches the encrypted video frames acquired from the first stream; an ECM from the second stream which is acquired by the set top box, the acquired ECM being associated with the cached acquired encrypted video frames; a control word (CW) derived by the set top box from the acquired ECM; a decryptor which decrypts the cached acquired encrypted video frames according to the CW; a locator which locates the at least one decrypted access point in the first stream; a second decryptor which decrypts encrypted video frames comprised in the cached first stream; a video decoder which decodes the decrypted video frames from the at least one decrypted access point; and a display outputting unit which displays the decoded decrypted video frames comprised in the first stream, beginning at the located at least one decrypted access point, wherein the decryptor, the second decryptor, the video decoder and the display outputting unit perform at better than real-time.

20. A system comprising: a tuner comprised in a set top box which tunes the set top box, the carrier frequency carrying a transport stream; a program association table (PAT) which is acquired from the transport stream by the set top box; a program map table (PMT) which is acquired by the set top box based on information in the PAT, acquiring; elementary streams indicated in the PMT which are acquired by the set top box, the elementary streams including at least: a stream comprising encrypted video frames, the encrypted video frames comprising at least one frame which comprises an encrypted access point; and an entitlement control word (ECM) stream; a cache which caches the acquired encrypted video frames; an ECM acquired by the set top box from the ECM stream; a control word (CW) derived by the set top box from the ECM; a decryptor which decrypts the cached acquired encrypted video frames according to the CW; a locator which locates the at least one decrypted access point in the cached video stream; a video decoder which decodes at least one decrypted video frame from the at least one decrypted access point; and a display outputting unit which displays the at least one decoded decrypted video frame beginning at the located at least one decrypted access point, wherein the decryptor and the video decoder perform at better than real-time.