Note: Descriptions are shown in the official language in which they were submitted.
CA 02437014 2010-07-27
1 UPGRADING OF ENCRYPTION
2
3 COPYRIGHT NOTICE
4 A portion of the disclosure of this patent document contains material which
is subject to copyright protection. The copyright owner has no objection to
the
6 facsimile reproduction of the patent document or the patent disclosure, as
it
7 appears in the Patent and Trademark Office patent file or records, but
otherwise
8 reserves all copyright rights whatsoever.
9
FIELD OF THE INVENTION
11 This invention relates generally to the field of digital video and
encryption
12 thereof. More particularly, this invention relates to an encryption method
and
13 apparatus particularly useful for encrypting packetized video content such
as that
14 provided by cable and satellite television systems.
16 BACKGROUND OF THE INVENTION
17 The related patents (7,336,787; 7,139,398; 7,124,303; 7,151,831;
18 7,127,619; 7,376,233; 7,302,059; 7,155,012; and, 7,292,690) describe
inventions
19 relating to various aspects of methods generally referred to herein as
partial
encryption or selective encryption. More particularly, systems are described
21 therein wherein selected portions of a particular selection of digital
content (e.g.,
22 a television program) are encrypted using two (or more) encryption
techniques
23 while other portions of the content are left unencrypted. By properly
selecting the
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.1 portions to be encrypted, the content can effectively be encrypted for use
under
2 multiple decryption systems without the necessity of encryption of the
entire
3 selection of content. In some embodiments, only a few percent of data
overhead
4 is needed to effectively encrypt the content using multiple encryption
systems. This
results in a cable or satellite system being able to utilize Set-top boxes
(STBs) or
6 other implementations of conditional access (CA) receivers from multiple
7 manufacturers in a single system - thus freeing the cable or satellite
company to
8 competitively shop for providers of Set-top boxes.
9
BRIEF DESCRIPTION OF THE DRAWINGS
11 The features of the invention believed to be novel are set forth with
12 particularity in the appended claims. The invention itself however, both as
to
13 organization and method of operation, together with objects and advantages
14 thereof, may be best understood by reference to the following detailed
description
of the invention, which describes certain exemplary embodiments of the
invention,
16 taken in conjunction with the accompanying drawings in which:
17 FIGURE 1 illustrates a chain of video object units as used in a Digital
18 Versatile Disc (DVD).
19 FIGURE 2 illustrates a dual partially encrypted DVD with a video chain
using
standard encryption consistent with certain embodiments of the present
invention.
21 FIGURE 3 illustrates a dual partially encrypted DVD with a video chain
using
22 a new encryption consistent with certain embodiments of the present
invention.
23 FIGURE 4 illustrates a partially encrypted DVD with a video chain using a
24 new encryption consistent with certain embodiments of the present
invention.
FIGURE 5 illustrates a product transition cycle consistent with certain
26 embodiments of the present invention.
27 FIGURE 6 illustrates a product transition cycle consistent with certain
28 embodiments of the present invention.
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CA 02437014 2010-07-27
1 FIGURE 7 illustrates a television Set top box that decrypts and decodes in'
2 a manner consistent with certain embodiments of the present invention.
3 FIGURE 8 is a flow chart depicting an encryption process consistent with
4 certain embodiments of the present invention.
6 DETAILED DESCRIPTION OF THE INVENTION
7 While this invention is susceptible of embodiment in many different forms,
8 there is shown in the drawings and will herein be described in detail
specific
9 embodiments, with the understanding that. the present disclosure is to be
considered as an example of the principles of the invention and not intended
to limit
11 the invention to the specific embodiments shown and described. In the
description
12 below, like. reference numerals are used to describe the same, similar or
13 corresponding parts in the several views of the drawings.
14 The terms "scramble" and "encrypt" and variations thereof are used
synonymously herein. Also, the term "television program" and similar terms can
16 be interpreted in the.normal conversational" sense, as well as a meaning
wherein
17 the term means any segment of A/V content that can be displayed on a
television
18 set or similar monitor device. The term "video" is often used herein to
embrace not
19 only true visual information, but also in the conversational sense (e.g.,
"video tape
recorder") to embrace not only video signals but associated audio and data.
The
21 term "legacy" as used herein refers to existing technology used for
existing package
22 medium and broadcast, cable and satellite systems such as existing
encryption
23 technology used at the launch of such a system. The exemplary embodiments
24 disclosed in the above patents and consistent with certain embodiments of
the
present invention are decoded by a television Set-Top Box (STB), but it is
26 contemplated that such technology will soon be incorporated within
television
27 receivers of all types whether housed in a separate enclosure alone or in
28 conjunction with recording and/or playback equipment or Conditional Access
(CA)
29 decryption module or within a television set itself. The present document
generally
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1 uses the example of a "dual partial encryption" embodiment, but those
skilled in the
2 art will recognize that the present invention can be utilized to realize
multiple partial
3 encryption without departing from the invention. Partial encryption and
selective
4 encryption are used synonymously herein. The term "package medium" and
similar
terms as used herein are intended to embrace a recording medium such as a
6 Digital Versatile Disc (DVD), Compact Disc (CD) or other magnetic, optical
or other
7 recorded medium that is generally merchandised as a package that. contains
the
8 electronic storage medium and is sold as a retail commodity, as contrasted
to an
9 electronically downloadable data stream.
In order to provide content control .and protection for both broadcast content
11 (whether by satellite, cable, pay-per-view or otherwise) as well as for
packaged
12 media such as Digital Versatile Discs (DVDs), various types of encryption
are often
13 . utilized. Either the entire content is encrypted under a given encryption
system
14 using a particular encryption technique, or the content is partially
encrypted using
a particular encryption technique.'
16 Unfortunately, as computing power grows, a single encryption technique or
17 a given encryption key may be rendered ineffective in thwarting those who
would
18 attempt to pirate the protected content. This problem has been recognized
in the
19 satellite and cable industry where it is common to make changes to
encryption
keys on a regular basis. For example, it is common for such'systems to change,
21 keys on a monthly basis. Moreover, although less frequent, it is
occasionally
22 advisable to upgrade the encryption process itself. By way of example, DES
(Data
23 Encryption Standard) encryption can be upgraded from 40 bit encryption to
56 bit
24 encryption to 128 bit encryption, etc. to enhance the security of the
encryption.
Unfortunately, even with these key sizes, with today's desktop computing
power,
26 it is feasible to hack an encryption key by brute force. In another
example, DES
27 encryption can be upgraded to a more sophisticated encryption algorithm
such as
28 Triple -DES, Advanced Encryption Standard (AES) or Common Scrambling
29 Algorithm (CSA). When this happens, upgrading of the software within a
television
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1 STB or equivalent device may require a software download or even a change in
2 hardware.
3 Similarly, encryption techniques used in packaged media may be subject to
4 being cracked by hackers and thus the security of the content compromised.
Such
is the case for the encryption algorithm originally released with the
introduction of
6 DVDs, which has been cracked and the decryption technique posted on the
7 Internet. While the problem is substantial in the case of a content
distributor such
8 as a cable system operator, in the case of package media such as DVDs, the
9 problem may even more complex since any encryption used in the packaged
medium should be compatible with playback equipment from any of dozens of
11 vendors (whereas, the cable or satellite system may be a closed environment
with
12 only one or a small limited number of approved vendors). Thus, until a
generational
13 change in encryption standards for the package medium can be made, the
content
14 may be compromised. Moreover, the user's existing content may become
obsolete
by any radical change in encryption introduced to prevent piracy. This may
make
16 it extremely difficult for equipment manufacturers to phase out equipment
in favor
17 of new equipment, since such changes might be rejected by the consumer:
Thus,
18 a transitional mechanism would be beneficial in order to make a transition
to a new
19 encryption standard which preserves the current encryption standard for a
while,
yet facilitates transition to a new standard.
21 In the above-referenced patents, a technique called dual partial
22 encryption or dual selective encryption is described. In this technique,
selective
23 portions of video and/or audio content are encrypted while other portions
are
24 transmitted unencrypted (clear). By appropriate selection of the content to
be
encrypted, a very high level of security of the content can be maintained at
the
26 sacrifice of minimal amounts of overhead. Since the amount of encrypted
content
27 is a small percentage of the overall,program content, that small portion
can be
28 duplicated and encrypted under several encryption schemes. This makes it
29 possible to decode the program on multiple decoders using multiple
decryption
schemes. The various encrypted portions in the above patents are
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1 distinguished by use of multiple program identifiers (PIDs). The present
invention
2 extends this concept to use in upgrading of encryption techniques for both
3 broadcast content and packaged media.
4 First consider the example of packaged media, and in particular for purposes
of this example (but without limitation) DVDs. DVDs are currently partially
6 encrypted with up to 25% of the overall content being encrypted and up to
50% of
7 any one sector being encrypted. However, the selected VOBU (video object
units -
8 a packet definition for packets of 2048 bytes used in DVDs) which are
currently
9 encrypted are not necessarily optimally selected. As the above-referenced
patents
applications have illustrated, by optimal selection of the content to be
encrypted,
11 a much lower percentage of packets can be encrypted to still effectively
render the
12 content well protected. The selection of content to be encrypted can be any
of the
13 selections identified in the above-referenced patents, such as, for
14 example without limitation, packets containing a video slice header,
packets
containing a video slice header appearing in an active region of a video
frame, any
16 packet carrying data representing an active region of a video frame, I
Frame
17 packets, packets containing motion vectors in a first P frame following an
I Frame,
18 packets having an intra_slice flag indicator set, packets having an intra
slice
19 indicator set, packets containing an intra_coded macroblock, packets that
carry
data for a slice containing an intra coded macroblock, packets containing data
21 from a first macroblock following the video slice header,packets containing
video
22 slice headers, packets containing anchor data, and P Frame packets for
23 progressively refreshed video data, packets occurring in a star pattern
24 approximately situated at approximately a center of an image, packets
carrying data
representing a pattern of horizontal'stripes across an image, packets carrying
data
26 representing a pattern of vertical stripes across an image, packets
carrying
27 information that is needed to decode the content, packets carrying a
payload that
28 comprises a packetized elementary stream (PES) header, samples of the video
29 content taken at prescribed sampling intervals, packets containing a
specified
elementary stream, and any other suitable packet selection criterion.
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1 Once a collection of VOBUs (packets) are selected for encryption, the
2 content is dual partial encrypted so that it has a clear portion, a portion
encrypted
3 using the old encryption process and a portion encrypted using the new
encryption
4 process. The dual partial encrypted video content is then stored on the DVD
so that
a first program chain references the clear portion and the portion encrypted.
using
6 the old encryption process, and so that a second program chain references
the
7 clear portion and the portion encrypted using the new encryption process.
Such
8 alternative program chains are currently used in some DVDs to provide
additional.
9 program content such as director cuts, different viewing angles, alternate
plots and
endings, and to provide parental control and alternative audio tracks. The
majority
11 of DVDs currently in production have only a single linear program chain.
12 A dual partially encrypted DVD (or other package medium such as a CD)
13 can thus be used as a transitional medium to facilitate conversion to the
new
14 encryption format. Consider, FIGURES 1-4 to understand the principles of
the
transition to a new encryption algorithm. - FIGURE 1 depicts a DVD which is
16 partially encrypted using the current standard CSS (Content Scrambling
System)
17 encryption system. In this figure, a selection of content contains a
sequence of
18 VOBUs (packets) having clear VOBUs 20 and encrypted VOBUs 24. The chain of
19 clear VOBUs 20 and encrypted VOBUs 24 together form a content selection
that
can be played back through a standard DVD player that understands and decrypts
21 CSS encrypted VOBUs.
22 FIGURES 2 and 3 depict a dual partially encrypted DVD consistent with
23 certain embodiments of the present invention. In these figures, the DVD
contains
24 the same chain of partially encrypted content made up of VOBUs 20 and 24 as
shown in FIGURE 1. Thus, a standard DVD player that decrypts CSS encrypted
26 VOBUs can play back the DVD depicted in FIGURE 2 by simply following the
27 program chain shown. A new DVD player can be introduced that also can play
28 back the DVD by following the program chain shown in FIGURE 3. The new DVD
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1 player need not be able to decode CSS encryption as long as it can decode a
new
2 encryption scheme (shown as NEW).
3 In this arrangement of FIGURE 3, the new DVD player utilizes a program
4 chain defined at the time of the manufacture of the DVD that bypasses VOBUs
24
in favor of VOBUs 28 that utilize the new encryption system. Such new DVD
6 players could be programmed to only recognize the program chain associated
with
7 the new encryption system, yet the same DVD could be backward compatible
with
8 CSS encryption as well as being compatible with the new system. The process
9 used to distinguish between the two encryption systems is similar to that
used for
parental control or separate viewing angles available on some currently
available
11 DVDs.
12 As applied to DVDs certain embodiments of the present invention would
13 select Video Object Unit packets which are important to the decoding of the
rest
14 of the content. The Units chosen for encryption would be duplicated and
scrambled
with CSS and a new improved algorithm. A new type of program chain called
16 "security" can be created that only the new players will understand and
respond to.
17 These would be similar to how parental rating program chains are managed.
Older
18 players will simply take the program chain containing CSS scrambled
packets.
19 New players would take the security program chain with the new algorithm
packets.
21 The use of CSS encrypted packets in one program chain assures that new
22 DVDs work in old DVD players. The duplicated and non-CSS scrambled packets
23 will not interfere with the old players. The duplicated packets using the
new
24 encryption algorithm can be encoded as alternate track or program chain
(PGC).
Thus, new players can be "forced" to take the program chain with the new
26 encryption algorithm automatically. Like camera angle branches, branches
for
27 encryption would be tightly interleaved together. These would likely use
Interleaved
28 Blocks (ILVB). So, in the case of the arrangements depicted in FIGURE 2-3,
the
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1 branches used for multiple encryption as depicted herein, are preferably
tightly
2 interleaved and preferably use Interleaved Blocks.
3 Once the marketplace has matured somewhat and the new encryption
4 system is standard, DVD manufacturers can begin phasing out dual encrypted
DVDs as shown in FIGURE 2-3 in favor of the format depicted in FIGURE 4. When
6 the market is mature enough, the new DVDs will only be compatible with new
DVD
7 players and only the new encryption system is needed. Alternatively, the-
new
8 DVDs can be dual partially encrypted with the next generation of encryption
9 technology in the same manner as shown in FIGURE 2-3.
Therefore, in accordance with certain embodiments consistent with the
11 present invention, multiple replacement encryption algorithms can be used
to
12 produce packaged media such as DVDs so that each DVD contains multiple
13 partially encrypted content. This will allow new players to actually phase
out
14 support for the older encryption algorithms since the older DVDs would
already
have the new algorithm encoded into them (even prior to marketing new
players).
16 Thus, as described, method of providing an upgrade for encryption used to
17 encrypt video content stored in a Digital Versatile Disc (DVD) from an old
18 encryption process to a new encryption process, consistent with certain
19 embodiments of the invention, involves selecting a portion of video content
for dual
partial encryption; dual partial encrypting the video content so that the
video content
21 has a clear portion, a portion encrypted using the old encryption process
and a
22 portion encrypted using the new encryption process; storing the dual
partial
23 encrypted video content on the DVD so that a first program chain references
the
24 clear portion and the. portion encrypted using the old encryption process,
and so
that a second program chain references the clear portion and the portion
encrypted
26 using the new encryption process.
27 Similarly, a method of providing an upgrade for encryption used for
28 encryption of video content stored in package medium from an old encryption
29 process to a new encryption process, consistent with certain embodiments of
the
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1 invention, involves selecting a portion of video content for selective
encryption;
2 duplicating the selected portion of content to produce first and second
copies of the
3 selected portion; encrypting the first copy of the selected portion using
the old
4 encryption process; encrypting the second copy of the selected portion using
the
new encryption process; storing the portion of the video content which is not
6 selected as clear content on the package medium; storing the encrypted first
copy
7 and the encrypted second copy of the selected portion on the package medium.
8 Thus, the transition path to a newer and more secure encryption method is
9 depicted in FIGURE 5 where initially, at 40, manufacturers of DVDs and DVD
players manufacture the players and media using the technique illustrated in
11 FIGURE 1 where only a single encryption process is used. During a
transitional
12 stage, the package media is dual partially encrypted to carry data
encrypted by both
13 the old encryption process and the new process at 44. Finally, at 48, the
transition
14 can be completed by phasing out the use of the original encryption process
entirely.
During the interim, at 44, players may be compatible with either encryption
system
16 or both and can still decode and play back the medium.
17 Consider now the application of dual partial encryption to the broadcast
18 content industry. In the US cable and satellite markets, the Data
Encryption
19 Standard (DES) is primarily in use. DES is quickly becoming obsolete. The
current
standard version of DES as used by the cable and satellite industry generally
uses
21 a 56-bit key. With the rapidly increasing processing capabilities of PCs,
decoding
22 by a brute force trial of all possible keys with one or more computers, is
rapidly,
23 becoming more feasible.
24 One of the most difficult things for a service provider to do is to upgrade
the
low level scrambling of a content delivery network. This is because of the
installed
26 base of decoders that perform decryption only based on the old encryption
process
27 and have no provision for upgrading the encryption. It is difficult for an
operator to
28 upgrade all the units in the field. This could potentially cost many
millions of
29 dollars. One possible solution is the use of Point of Deployment (POD)
modules.
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1 When they are deployed, POD modules will provide one method of changing the
2 low level scrambling used in a network. This is accomplished by wholesale
3 replacement of all PODs in the network. However, even replacing POD modules
4 can be costly, and this avenue is not available for decoders that do not
support
PODs. As of this date, PODs have only been deployed in limited numbers in the
6 US cable market. Using current technology, new scrambling cannot be used
until
7 all the units or modules doing the old encryption are removed from the
field. This
8 is a logistical and financial problem as mentioned earlier. The invention
allows new
9 Set-top boxes and other decoding devices to be introduced without the need
to
make legacy STBs and other decoders obsolete. As an impetus to replace older
11 units, the service operator may withhold new services to these devices, an
thus
12 compel the users to get new units (performing the new algorithm) to get the
new
13 services.
14 Accordingly, the progression for transition to a new encryption algorithm
for
cable and satellite operators (and similar content providers) is similar to
that
16 depicted in FIGURE 5 and is illustrated more explicitly in FIGURE 6. In
this figure;
17 the current encryption algorithm is depicted at 60 with a transitional
phase at 64
18 being used to transition from an old encryption algorithm to a newer
algorithm as
19 new STBs or PODs are introduced. When a large installed base of newer STBs
is achieved, the new encryption algorithm may be used exclusively at 68.
21 Thus, in accordance with certain embodiments of the present invention, a
22 method of upgrading an encryption process for encryption of video
information from
23 an old encryption process to a new encryption process involves selecting a
portion
24 of video content for selective encryption; duplicating the selected portion
of content
to produce first and second copies of the selected portion; encrypting the
first copy
26 of the selected portion using the old encryption process; and encrypting
the second
27 copy of the selected portion using the new encryption process.
28 In order to achieve the desired dual partial encryption according to the
29 present invention for making a transition between two encryption
algorithms, a
newly deployed decoder (e.g., a STB) is provided with a mechanism to
distinguish
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1 the encrypted portions of the program material. This is accomplished in the
2 manner described in the above-referenced patents. In one preferred
3 method, the dual encrypted packets are distinguished by use of separate
Program
4 Identifiers (PIDs). That is, clear packets are identified by a first packet
identifier.
Dual encrypted packets are identified by a pair of PIDs that distinguish the
new
6 encryption system from the old. For example, PID 101 can be associated with
7 clear packets as well as packets encrypted under the old encryption system.
PID
8 102 can be used to identify packets encrypted under the new encryption
system
9 and is referred to as a secondary PID or shadow PID. The new STB is provided
with the PIDs associated with the program and then decodes the program by
11 ignoring encrypted packets with PID 101 in favor of encrypted packets with
PID
12 102. This process is described in detail in the above-referenced patents.
13
14 In accordance with certain embodiments consistent with the present
invention, a selectively encrypted digital video signal can be embodied in a
carrier
16 wave, that has a stream of packets of video data, wherein the stream of
packets
17 when not encrypted represent a segment of video content; certain of the
packets
18 being unencrypted and certain of the packets being encrypted under a legacy
19 encryption method and certain of the packets being encrypted under a
replacement
encryption method; a first segment of code that identifies the unencrypted
packets
21 by a first packet identifier (PID); and a second segment of code that
identifies the
22 encrypted packets by a second packet identifier (PID).
23 An authorized Set-top box such as 100 illustrated in FIGURE 7 operating
24 under the new encryption system decrypts and decodes the incoming program
by
recognizing both primary and secondary PIDs associated with a single program.
26 The multiplexed video data stream containing both PlDs is directed to a
27 demultiplexer 104. When a program is received that contains encrypted
content
28 that was encrypted by any of the selective encryption techniques described
in the
29 above-referenced patents, the demultiplexer directs encrypted packets
containing content encrypted under the new encryption algorithm and secondary
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1 PIDS to a decrypter 108 that decrypts the packets encrypted under the new
2 encryption system. After these packets are decrypted at 108, they are passed
to
3 a PID remapper 112. As illustrated, the PID remapper 112 receives packets
that
4 are unencrypted and bear the primary PID as well as the decrypted packets
having
the secondary PID. The PID remapper 112 combines the decrypted packets from
6 decrypter 108 with the unencrypted packets having the primary PID to produce
an
7 unencrypted data stream representing the desired program. PID remapping is
8 used to change either the primary or secondary PID or both to a single PID.
This
9 unencrypted data stream can then be decoded normally by decoder 116. Some or
all of the components depicted in FIGURE 7 can be implemented as program code
11 running on a programmed processor running code stored on an electronic
storage
12 medium.
13 In one embodiment of the case of package media consistent with the
14 present invention, the decoder or player used to decode the content
encrypted
under the new encryption algorithm may be functionally identical to a
conventional
16 decoder or player except for the substitution of a different decrypter or
different
17 decryption algorithm. In other exemplary embodiments, the decoder or player
can
18 be designed to recognize newly encrypted program chains while ignoring
program
19 chains associated with the old encryption algorithm.
In other embodiments consistent with the present invention, a method of
21 playback of content stored on a recording medium involves reading a portion
of the
22 recording medium to determine that the recording medium contains content
23 containing portions encrypted under multiple encryption techniques;
selecting
24 content having portions encrypted under one of the multiple encryption
techniques;
and playing the content, wherein the playing comprises decrypting the
encrypted
26 portion of the content.
27 FIGURE 8 is a flow chart 150 that broadly illustrates the encryption
process
28 consistent with certain embodiments of the present invention starting at
154. At
29 158 the VOBU or other packet type that is to be encrypted is specified. In
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4
1 accordance with certain embodiments consistent with the present invention,
the
2 selected packet type may be any of the packets described above that
generally
3 contain data that makes it difficult to decode the content. Packets are then
4 examined at 162 to identify packets of the specified type. At 166, the
identified
packets are duplicated and at 170 one set of these packets is encrypted under
a
6 the old "legacy" encryption method. The other set of identified packets is
encrypted
7 at 174 under a the new encryption method that is designed to replace the
legacy
8 encryption method. The originally identified packets are then replaced in
the data
9 with the two sets of encrypted packets at 180 and the process ends at 186.
In
certain embodiments, other steps are taken such as indexing the two program
11 chains in the package medium, etc..
12 Thus, a method of upgrading an encryption process for encryption of video
13 information from an old encryption process to a new encryption process,
consistent
14 with certain embodiments involves selecting a portion of video content for
selective
encryption. The selected portion is duplicated to produce first and second
copies.
16 of the selected portion. The first copy is encrypted using the old
encryption process
17 and the second copy is encrypted using the new encryption process to
produce a
18 dual partially encrypted segment of video information that can either be
broadcast
19 over a cable or satellite system or stored in a package medium, for
example, as
two program chains. '
21 Those skilled in the art will recognize that the present invention has been
22 described in terms of exemplary embodiments based upon use of a programmed
23 processor. However, the invention should not be so limited, since the
present
24 invention could be implemented using hardware component equivalents such as
special purpose hardware and/or dedicated processors which are equivalents to
26 the invention as described and claimed. Similarly, general purpose
computers,
27 microprocessor based computers, micro-controllers, optical computers,
analog
28 computers, dedicated processors and/or dedicated hard wired logic may be
used
29 to construct alternative equivalent embodiments of the present invention.
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1 Those skilled in the art will appreciate that the program steps and
associated
2 data used to implement the embodiments described above can be implemented
3 using disc storage as well as other forms of storage such as for example
Read
4 Only Memory (ROM) devices, Random Access Memory (RAM) devices; optical
storage elements, magnetic storage elements, magneto-optical storage elements,
6 flash memory, core memory and/or other equivalent storage technologies
without
7 departing from the present invention. Such alternative storage devices
should be
8 considered equivalents.
9 The present invention, as described in embodiments herein, is implemented
using a programmed processor executing programming instructions that are
11 broadly described above form that can be stored on any suitable electronic
storage
12 medium or transmitted over any suitable electronic communication medium or
13 otherwise be present in any computer readable or propagation medium.
However,
14 those skilled in the art will appreciate that the processes described above
can be
implemented in any number of variations and in many suitable programming
16 languages without departing from the present invention. For example, the
order of
17 certain operations carried out can often be varied, additional operations
can be
18 added or operations can be deleted without departing from the invention.
Error
19 trapping can be added and/or enhanced and variations can be made in user
interface and information presentation without departing from the present
invention.
21 Such variations are contemplated and considered equivalent.
22 Software code and/or data embodying certain aspects of the present
23 invention may be present in any computer readable medium, transmission
24 medium, storage medium or propagation medium including, but not limited to,
electronic storage devices such as those described above, as well as carrier
26 waves, electronic signals, data structures (e.g., trees, linked lists,
tables, packets,
27 frames, etc.) optical signals, propagated signals, broadcast signals,
transmission
28 media (e.g., circuit connection, cable, twisted pair, fiber optic cables,
waveguides,
29 antennas, etc.) and other media that stores, carries or passes the code
and/or data.
Such media may either store the software code and/or data or serve to
transport
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1 the code and/or data from one location to another. In the present exemplary
2 embodiments, MPEG compliant packets, slices, tables and other data
structures
3 are used, but this should not be considered limiting since other data
structures can
4 similarly be used without departing from the present invention.
While the invention has been described in conjunction with specific
6 embodiments, it is evident that many alternatives, modifications,
permutations and
7 variations will become apparent to those skilled in the art in light of the
foregoing
8 description. Accordingly, it is intended that the present invention embrace
all such
9 alternatives, modifications and variations as fall within the scope of the
appended
claims.
11 S
12
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