Patent Publication Number: US-2011066437-A1

Title: Methods and apparatus to monitor media exposure using content-aware watermarks

Description:
RELATED APPLICATION 
     This patent claims the benefit of U.S. Provisional Patent Application Ser. No. 61/147,363, filed Jan. 26, 2009, which is hereby incorporated herein in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to audience measurement and, more particularly, to methods and apparatus to monitor media exposure using content-aware watermarks. 
     BACKGROUND 
     Media-centric companies are often interested in tracking the number of times that audience members are exposed to media compositions (e.g., television programs, motion pictures, internet videos, radio programs, etc.). To track such exposures, companies often generate audio and/or video signatures (e.g., a representation of some, preferably unique, portion of the media composition or the signal used to transport the media composition) of media compositions that can be used to determine when those media compositions are presented to audience members. Additionally, companies broadcast identification codes with media compositions to monitor presentation of those media compositions to audience members by comparing identification codes retrieved from media compositions presented to audience members with reference to identification codes stored in a reference database in association with information descriptive of the media compositions. These identification codes can also be referred to as watermarks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example media network system used to encode media compositions or media presentations (e.g., audio files, media files, audio streams, video streams, etc.) with content-aware watermarks, to transmit the encoded content to audience members, and to decode the content-aware watermarks to collect audience measurement data. 
         FIG. 2A  depicts an example media excerpt to be used by a content-aware watermark encoder of  FIG. 1  to generate a content-aware watermark. 
         FIG. 2B  illustrates an example conventional audience measurement code. 
         FIG. 2C  illustrates an example content aware watermark. 
         FIG. 2D  illustrates another example content aware watermark. 
         FIG. 2E  illustrates still another example content aware watermark. 
         FIG. 3  is a block diagram of an example apparatus that may be used to implement the example content-aware watermark encoder of  FIGS. 1 and 2 . 
         FIG. 4A  is a block diagram of an example apparatus that may be used to implement the example content-aware watermark decoder of  FIG. 1  shown in communication with the example central facility of  FIG. 1 . 
         FIG. 4B  is a block diagram of an example apparatus that may be used to generate the example code book of  FIGS. 1 and 4A . 
         FIGS. 5A and 5B  are a flow diagram representative of example machine readable instructions that may be executed to implement the example content-aware watermark encoder of  FIGS. 1-3  to construct content-aware watermarks and to embed the content-aware watermarks into media compositions. 
         FIG. 6  is a flow diagram representative of example machine readable instructions that may be executed to implement the example content-aware watermark decoder of  FIGS. 1 and 4A  to detect, decode, and transmit information associated with content-aware watermarks. 
         FIG. 7  is a flow diagram representative of example machine readable instructions that may be executed to implement the example central facility of  FIGS. 1 and 4A  to process information received from the example decoder of  FIGS. 1 and 4A . 
         FIG. 8  is a flow diagram representative of example machine readable instructions that may be executed to implement the example code book of  FIGS. 1 ,  4 A, and/or  4 B to associate one or more proxy codes with one or more keywords. 
         FIG. 9  is a block diagram of an example processor system that may be used to execute the machine readable instructions of  FIGS. 5A and 5B  to implement the encoder of  FIGS. 1-3 , to execute the machine readable instructions of  FIG. 6  to implement the decoder of  FIGS. 1 and 4A , to execute the machine readable instructions of  FIG. 7  to implement the example central facility of  FIGS. 1 and 4A , and/or to execute the machine readable instructions of  FIG. 8  to implement the example code book of  FIGS. 1 ,  4 A, and/or  4 B. 
     
    
    
     DETAILED DESCRIPTION 
     Although the following discloses example methods, apparatus, systems, and/or articles of manufacture including, among other components, firmware and/or software executed on hardware, it should be noted that such methods, apparatus, systems, and/or articles of manufacture are merely illustrative and should not be considered as limiting. For example, it is contemplated that any or all of these firmware, hardware, and/or software components could be embodied exclusively in hardware, exclusively in software, exclusively in firmware, or in any combination of hardware, software, and/or firmware. Accordingly, while the following describes example methods, apparatus, systems, and/or articles of manufacture, the examples provided are not the only way(s) to implement such methods, apparatus, systems, and/or articles of manufacture. 
     The example methods, apparatus, systems, and/or articles of manufacture described herein can be used to construct, encode, transmit, and/or decode watermarks. A watermark is information (e.g., a code) that is embedded in or otherwise associated with audio/video content prior to broadcast. The watermarks described herein can be extracted and/or collected at a downstream location (e.g., a monitored home or business) to enable identification of the audio and/or video content, the source of the audio and/or video content, and/or the specific content of the audio and/or video content. In some instances, a watermark may be used to establish ownership of audio/video media content. In such instances, the watermark is directly or indirectly indicative of a particular content owner and/or licensee. Additionally or alternatively, in some examples, a watermark can be used to identify the associated audio/video media composition and/or the source (e.g., distributor) of the same by comparing the watermark to codes stored in a reference database in association with respective audio/video identifiers (e.g., titles, program names, etc.) and/or source names (e.g., Cable News Network (CNN™)). 
     In the past, other than referencing the program in general (e.g., the program title or the station broadcasting the program), watermarks did not include information that alone was indicative of the specific content (e.g., characters, plot, product placements, etc.) of the audio and/or video media compositions with which the watermarks were associated. In contrast, as described in commonly assigned U.S. patent application Ser. No. 12/101,738, which is incorporated herein by reference in its entirety, content-aware watermarks include and/or refer to descriptive information representing the specific audio/video content of their respective media compositions at specific points in time. In other examples, the content-aware watermarks may include content-descriptive information generally corresponding to the locations in the audio/video composition at which the content-aware watermarks are embedded or otherwise associated with. For example, a content-aware watermark associated with a scene of an audio/video program may identify a product or service (e.g., a soft drink, a financial service, a retail establishment chain, etc.) appearing (e.g., advertised) in that scene. Additionally or alternatively, a content-aware watermark embedded in or otherwise associated with audio/video content may include information indicative of a character (e.g., a role in a television program) and/or actor appearing (e.g., performing) in a scene that occurs at a time that occurs at generally the broadcast time of the content-aware watermark. Additionally or alternatively, a content-aware watermark embedded in or otherwise associated with audio/video content may include information indicative of a topic (e.g., current news, such as a political campaign or the participants thereof) being discussed in the content at a time that occurs at generally the broadcast time of the content-aware watermark. 
     To generate the content-descriptive information, an apparatus is configured to select certain words or phrases from the media content to be encoded. The words can be manually input/identified and/or automatically identified using, for example, closed captioning information, a speech-to-text converter, detected metadata (e.g., title, program name, international standard audiovisual number (ISAN), or any other identifier information), detected scene changes, detected blank frames or MPEG splice points, and/or detected logos. Preferably, the selected terms are representative of some aspect of the audio/video content of interest (e.g., embedded advertisement, actor, character, etc.). The selected word(s) or phrase(s) are then used as keyword(s) that are associated with a watermark. The watermark is then embedded into or otherwise associated with the media content for broadcast with the content. 
     The encoded content-aware watermarks can be used to detect when people or audience members are exposed to or consume particular media content associated with the content-aware watermarks. For example, a meter installed to monitor media exposure can detect the content-aware watermarks. The content-aware watermarks can be used (at the meter or at a central facility) to lookup keywords in a database to determine the product(s), advertisement(s), brand(s), character(s), and/or discussed topic(s) to which the household members were exposed. The extracted watermarks and/or keywords contained therein can be forwarded to a central facility via, for example, a network connection. The central facility performs one or more analyses using the extracted watermarks and/or keywords. Example analyses include developing specific ratings for scene(s), character(s), actor(s), brand(s), product(s), advertisement(s), topic(s), etc. 
     The above described content-aware watermarks and their advantages are fully disclosed in U.S. patent application Ser. No. 12/101,738. It has been recognized by the inventors of the instant application that the noted content-aware watermarks, while advantageous in many respects, are difficult to utilize because of the severe bandwidth restrictions associated with encoding media content with audience measurement codes. In particular, it is very important to ensure that codes added to broadcast content do not perceptibly reduce the quality of the broadcast content and that the codes themselves are not humanly perceptible by audience members. To balance these concerns, the assignee of this patent has traditionally cooperated with broadcasters to encode broadcast content with masked or psycho-acoustically masked source identification codes comprising 38 bits every two and one-half seconds. In the past, the codes included six characters that identify the source of the content (e.g., the broadcaster&#39;s call sign such as ABC™). The remaining portion of the 38 bits were utilized to provide a timestamp substantially corresponding to a broadcast date and time (with time resolution at the seconds level). 
     The above encoding approach provides valuable audience measurement data. Because the codes are collectible by an audience measurement meter, the audience measurement entity operating the meter can identify the broadcaster and time of broadcast for every encoded media content exposed to the meter. By comparing the broadcaster and time of broadcast information extracted from the code to a schedule reflecting broadcast content by time and broadcaster, the audience measurement entity can specifically identify the media content to which the meter was exposed and, thus, draw conclusions about the media usage habits of populations of interest. 
     Due to the prevalence of remote control devices that enable audience members to easily change the channel tuned to by information presentation devices such as televisions by merely pushing a button, channel hopping (also colloquially referred to as “channel surfing”) is common. As a result of such channel hopping, it is desirable to retain the granularity of the above-noted current audience measurement coding approach (i.e., transmitting the call sign and timestamp every two and one half seconds) to track channel changes that occur during channel hoping. Therefore, a challenge is presented as to how to utilize the above-noted content-aware watermarks without diluting the granularity of the current audience measurement approach while maintaining the imperceptibility to the human ear of existing codes. 
     One approach to this problem would be to add a second layer of encoding to the present audience measurement approach by, for example, encoding broadcast content with the content-aware watermarks at a different location of the signal without disturbing the current audience measurement coding approach. Thus, for example, the content-aware watermarks could be added as a second code to the audience measurement codes already employed (i.e., the codes reflecting the call sign and timestamp). One possible location for such a second code would be in a high frequency component of the video or audio portion of the broadcast signal. While it might not be practical to detect such a high frequency code in, for example, a monitored location such as an audience member&#39;s home or a restaurant, such a code could be detected at a dedicated audience measurement location such as by Nielsen&#39;s Monitor Plus locations (i.e., electronics in specific geographic locations that include a plurality of tuners dedicated to advertising monitoring). 
     Using a second code is disadvantageous in that it requires modifications to audience measurement meters (i.e., creating new meters and/or altering existing meters) to detect such codes. In addition, broadcasters are very reluctant to allow audience measurement companies to insert additional codes into their content due to concerns with possible negative effects on the quality of the viewer experience. 
     A second approach is to replace the existing audience measurement code (i.e., both the call sign and the timestamp) with a content-aware watermark containing the content to be tracked (e.g., nouns reflecting the actor name, the topic being discussed, keywords, products displayed in a corresponding scene, etc.) at some periodic or a-periodic intervals. However, such an approach inherently removes information from the existing audience measurement codes, thereby diluting the granularity of the information collected by the audience measurement system. 
     In view of the above noted concerns, the present disclosure seeks to modify the existing audience measurement coding approach to accommodate content-aware watermarks with little or no dilution in granularity such that channel changes associated with, for example, channel hoping, remain detectible. In particular, rather than inserting the terms for the content specific information being tracked into the watermarks, example systems, apparatus, methods, and articles of manufacture described herein either: (a) prepend or append a short proxy code to the call letter in the existing audience measurement code to create a content-aware watermark and employ a code book correlating the short proxy codes to the content to be tracked (e.g., words reflecting the actor name, the topic being discussed, keywords, products displayed in a corresponding scene, etc.) to decipher the meaning of the proxy code in the content-aware watermark, or (b) replace the call letter in the existing audience measurement code with the short proxy code and employ a code book correlating the short proxy codes to the content to be tracked to decipher the meaning of the proxy code in the content-aware watermark. Preferably, the size of the content-aware code (i.e., the original code modified to include the proxy codes) is the same or substantially the same as the size of the original code. As a result, the existing audience measurement coding approach is used to convey more information with little or no loss of granularity and without requiring substantial changes to the encoding and/or detecting apparatus and/or methodology of the existing audience measurement system. 
     The example methods, systems, apparatus, and/or articles of manufacture described herein enable content-descriptive keywords of the content-aware watermarks discussed above and in U.S. patent application Ser. No. 12/101,738 to be efficiently encoded using proxy codes to, for example, decrease the amount of bandwidth needed to encode and/or transmit those keywords. In some instances, the proxy codes are mapped to sounds (e.g., phonetics or phonemes). For example, a word (e.g., a string of text) can be broken down into one or more sounds (e.g., phonetics or phonemes) that represent an approximate pronunciation of the word. The individual sounds can be represented by one or more symbols (e.g., characters or notations that are selected from a collection or library of phonetic notations, such as the International Phonetic Alphabet (IPA)). A unique proxy code (e.g., a value represented by, for example, a binary or hexadecimal word or digit) is then assigned to corresponding ones of the sounds (e.g., phonetic notations of the IPA). In some examples, the proxy codes and the associated phonetic notations are stored in a code book located at a central facility. The central facility may include a master code book encompassing all proxy codes, different code books for different types of media (e.g., movies, television programs, radio broadcasting, etc.), and/or different code books for different instances of media (e.g., one code book for a first television program and a second, different code book for a second television program). 
     In some implementations described herein, when an extracted keyword to be represented by a content-aware watermark is broken down into individual phonetic notations, the proxy codes corresponding to the phonetic notations for the keyword are inserted (e.g., appended or prepended to a call sign) into the conventional code to form a content-aware watermark. Preferably, the proxy codes corresponding to the phonetic representation of the keywords require less bandwidth than the keywords themselves. As described in greater detail below, after the content-aware watermarks are detected and, in some instances, conveyed to a central facility, the proxy codes corresponding to the phonetic representation of the keyword(s) are used as indices into a code book to reconstruct the phonetic representation and, subsequently, the content-descriptive information. 
     All of the proxy codes needed to represent a keyword may be placed in the same content-aware watermark or the proxy code may be spread across multiple content-aware watermarks. For example, if “Dylan” is represented by codes [003], [011], and [015], code [003] may be sent in a first content-aware watermark, code [011] may be sent in a second content-aware watermark, and code [015] may be sent in a third content-aware watermark. Preferably, the first, second, and third watermarks are sent sequentially. 
     In some examples, rather than or in addition to using phonetic encoding, some or all of the keywords to be encoded may be selected based on the current popularity of topics, persons, products, programs, and/or any other media content. The popularity of such media content is measured by, for example, measuring a frequency of occurrence throughout a defined set of media presentations (e.g., the number of times a celebrity&#39;s name was uttered during a previous month on one or more television station(s) having one or more programs dedicated to the discussion of celebrities). The selected keyword(s) are then recorded in a code book that maps each keyword to a unique proxy code. When keywords are extracted from the media content to create content-aware watermarks, the code book is referenced to obtain the corresponding proxy code (e.g., a value represented by, for example, a binary or hexadecimal word or digit) corresponding to the extracted keywords. Preferably, the code book is structured such that the proxy codes corresponding to highly popular keywords generally contain fewer bits of data than the proxy codes corresponding to less popular keywords. In some examples, where a keyword is encountered that does not have an assigned value in the popular keyword code book, the example methods, systems, apparatus, and/or articles of manufacture described herein are configured to phonetically encode the keyword, as described above. In such instances, a status indicator (e.g., a dedicated bit position) may be added to the content-aware watermark to indicate which type of encoding occurred when creating the content-aware watermark (e.g., phonetic encoding or encoding according to the popularity of selected keywords). A similar status indicator can indicate the start and/or end of a series of content-aware watermarks carrying a series of proxy codes that together correspond to one keyword (e.g., a series of phonetic codes). 
     Turning to  FIG. 1 , an example media network system 100 used to communicate media compositions or media presentations (e.g., audio files, media files, audio streams, and/or video streams) to audience members includes a plurality of media servers  102   a - e  to store video/audio media for retrieval by audience members and/or for broadcasting to audience members. In the illustrated example, each of the servers  102   a - e  includes a respective content-aware watermark (CAW) encoder  104  to generate content-aware watermarks based on media content stored therein and to embed or otherwise associate the content-aware watermarks with respective media content. Although in the illustrated example of  FIG. 1  each of the media servers  102   a - e  is provided with its own content-aware watermark encoder  104 , in other example implementations, the content-aware watermark encoders  104  may not be installed in the media servers  102   a - e  and may instead be installed at central media encoding servers such as, for example, an encoding server  106  at a central facility  108 . In this manner, media content to be encoded with content-aware watermarks may be communicated to the central facility  108  and the encoding server  106  can encode the media content with respective content-aware watermarks and communicate the encoded media content to the respective media servers. In other example implementations, some of the media servers  102   a - e  may be provided with the content-aware watermark encoders  104  while others may use the encoding server  106  at the central facility for content-aware watermarking encoding services. As described below in connection with  FIGS. 2A ,  2 B,  3 ,  5 A, and  5 B, the content-aware watermark encoders  104  and/or  106  are configured to implement the example methods, systems, apparatus, and/or articles of manufacture described herein to construct and encode the content-aware watermarks in a manner that requires a minimal amount of bandwidth (e.g., preferably the same or substantially the same amount of bandwidth used by existing conventional codes) while maintaining the granularity of data associated with codes already present in the media content. 
     In the illustrated example, a personal computer  110  may be coupled via a network  112  (e.g., the Internet) to the internet video media server  102   a,  the internet audio content media server  102   b,  and/or the advertising media server  102   c.  The personal computer  110  may be used to decode and present media content received from any of those servers  102   a - c.  Additionally, the personal computer  110  includes a content-aware watermark decoder  114  to extract content-aware watermarks from presented media content, to extract the proxy codes from the content-aware watermarks, and/or to decode keywords from the proxy codes. Further, the content-aware watermark decoders  114  are configured to transmit extracted information associated with the content-aware watermarks (e.g., proxy codes) and/or the content-aware watermarks themselves to, for example, the central facility  108  for subsequent analysis. For example, an analysis server  116  in the central facility  108  can use content-descriptive information extracted from the content-aware watermarks (e.g., via the proxy codes) to determine the number of times that users of the personal computer  110  were exposed to particular media content or to advertisements for particular products or brands and/or the time and date of such exposure(s). That is, if a detected keyword corresponds to the name of a financial service, the analysis server  116  can determine the number of times that users of the personal computer  110  were exposed to the name of that financial service (whether in an advertisement or elsewhere (e.g., in a news story)) based on the number of times the personal computer  110  communicates the same financial service keyword (or the proxy code corresponding to such keywords) to the central facility  108 . In some examples, the analysis server  116  compares received proxy codes to codes stored in a reference database  118  to identify the corresponding keyword(s), media identifier(s), brand name(s), product name(s), product type(s), character name(s), person(s), topic(s), etc. 
     The reference database  118  stores terms of interest that are to be selected from media compositions for encoding into content-aware watermarks to be embedded in the media compositions. In other words, the terms of interest stored in the reference database  118  are the keywords that comprise the content-descriptive information of the content-aware watermarks. Additionally, the reference database  118  is configured to store one or more code books  119  (which are described below in connection with  FIGS. 4A ,  4 B, and  8 ) mapping keywords and/or phonetic notations to the proxy codes to be encoded in content-aware watermarks. When the decoders  114  extract the proxy codes from content-aware watermarks and communicate the proxy codes to the central facility  108 , the analysis server  116  compares the received proxy codes to entries in a code book  119  to identify the keywords and/or phonetic keywords (e.g., phonetic representations that can be reconstructed to form one or more keywords). The identified keywords can be used to determine exposures to particular media content. 
     When the received proxy codes are associated with phonetic notations in a phonetic code book  119  (e.g., as a result of a previous phonetic to proxy code mapping), a phonetic converter  120  of the central facility  108  is used to reassemble keywords from the phonetic notations gathered from the code book  119 . The example phonetic converter  120  of  FIG. 1  is described in greater detail below in connection with  FIGS. 4A and 7 . 
     Once the keywords have been obtained (e.g., after being mapped using a code book  119  and, in some instances, reassembled using the phonetic converter  120 ), the analysis server  116  stores exposure levels for the keywords in an exposure database  121 . Because the keywords can represent advertisements, actors, products, brands, audio and/or video media, etc., the exposure levels for the keywords can represent exposure levels for any of these as well. 
     In some example implementations, the personal computer  110  may be configured to execute analysis processes to perform at least some or all of the analyses described above as being performed at the central facility  108  by the analysis server  116 . In such example implementations, the personal computer  110  communicates the results of its analyses to the central facility  108  for storage in the exposure database  121  and/or for further processing by the analysis server  116 . In yet other example implementations, the personal computer  110  may not extract proxy codes from content-aware watermarks but may instead communicate the content-aware watermarks to the central facility  108 . The analysis server  116  may then extract the keywords using the proxy codes from the content-aware watermarks for subsequent analysis. 
     In the illustrated example, a television  122  receives media content from the advertising media server  102   c,  the television media server  102   d,  and/or the motion picture media server  102   e  via a mediacast network  124 . The mediacast network  124  may be an analog and/or digital broadcast network, a multicast network, and/or a unicast network. In the illustrated example, the television  122  is coupled to a media meter  126  having a content-aware watermark decoder  114  to extract content-aware watermarks from presented media content, to extract proxy codes from the content-aware watermarks, and/or to identify and decode keywords from the proxy codes. The decoder  114  of the media meter  126  is substantially similar or identical to the decoder  114  of the personal computer  110 . In addition, the media meter  126  operates in substantially the same manner as the personal computer  110  with respect to extracting, decoding, and/or, processing content-aware watermarks. That is, the media meter  126  can be configured to extract proxy codes corresponding to keywords (or phonetic representations thereof) from content-aware watermarks and to communicate the proxy codes to the central facility  108 . Additionally or alternatively, the media meter  126  can communicate the content-aware watermarks to the central facility  108  so that the analysis server  116  at the central facility can extract the proxy codes and identify the corresponding keywords. In some example implementations, the media meter  126  may be configured to analyze the keywords to determine media exposure and may communicate the analysis results to the central facility  108  for storage in the exposure database  121  and/or for further processing by the analysis server  116 . 
     While an example manner of implementing the media network system  100  has been illustrated in  FIG. 1 , one or more of the elements, processes and/or devices illustrated in  FIG. 1  may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example media servers  102   a - e,  the example content-aware encoder  104 , the example encoding server  106 , the example personal computer  110 , the example network  112 , the example content-aware watermark decoder  114 , the example analysis server  116 , the example reference database  118 , the example code books  119 , the example phonetic converter  120 , the example exposure database  121 , the example mediacast network  124 , the example media meter  126 , and/or, more generally, the example media network system  100  of  FIG. 1  may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example media servers  102   a - e,  the example content-aware encoder  104 , the example encoding server  106 , the example personal computer  110 , the example network  112 , the example content-aware watermark decoder  114 , the example analysis server  116 , the example reference database  118 , the example code books  119 , the example phonetic converter  120 , the example exposure database  121 , the example mediacast network  124 , the example media meter  126 , and/or, more generally, the example media network system  100  of  FIG. 1  could be implemented by one or more circuit(s), programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)), etc. When any of the appended claims are read to cover a purely software and/or firmware implementation, at least one of the example media servers  102   a - e,  the example content-aware encoder  104 , the example encoding server  106 , the example personal computer  110 , the example network  112 , the example content-aware watermark decoder  114 , the example analysis server  116 , the example reference database  118 , the example code books  119 , the example phonetic converter  120 , the example exposure database  121 , the example mediacast network  124 , the example media meter  126 , and/or, more generally, the example media network system  100  of  FIG. 1  are hereby expressly defined to include a tangible medium such as a memory, DVD, CD, etc. storing the software and/or firmware. Further still, the example media network system  100  of  FIG. 1  may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in  FIG. 1 , and/or may include more than one of any or all of the illustrated elements, processes and devices. 
       FIG. 2A  depicts an example media excerpt  202  having closed caption text  204  used by the content-aware watermark encoder  104  of  FIG. 1  to generate a content-aware watermark  206 . In other examples, as described below, additional or alternative methods and/or sources (other than the closed caption text  204 ) can be utilized to generate the content-aware watermark  206 . In the illustrated example, the content-aware watermark encoder  104  receives the closed caption text  204  of the media excerpt  202  that recites “New York loves Bubblee brand soda” and selects one or more keywords indicative of the media content presented in the media excerpt  202 . In the illustrated example, the content-aware watermark encoder  104  selects the terms ‘New York,’ ‘Bubblee,’ and ‘soda.’ The term ‘New York’ indicates that the advertisement corresponding to the media excerpt  202  is directed to residents of New York City, areas surrounding New York City, and/or to others that like New York City or have an affiliation with New York City. The term ‘Bubblee’ identifies the trade name of the product being advertised. The term ‘soda’ identifies the type of product being advertised. 
     After the encoder  104  selects the term(s) or phrase(s) to be used as the content-descriptive keyword(s), the encoder  104  generates and/or obtains one of the encoding representations described herein. In the illustrated example, the encoder  104  is configured to either (1) generate phonetic notations for the keywords and to assign or retrieve the proxy codes associated therewith, and/or (2) to assign or retrieve the proxy codes directly associated with the keywords themselves (e.g., one of a plurality of keywords selected based on a popularity measurement). To retrieve the proxy codes associated with the phonetic notations, the encoder  104  references the phonetic code book  119   a  stored at the central facility  108 . In the illustrated example, the phonetic code book  119   a  maps phonemes to unique proxy codes. To retrieve the proxy codes that are mapped to specific keywords, the keyword code book  119   b  stores proxy codes  208  in association with respective ones of the keyword terms ‘New York,’ ‘Bubblee,’ and ‘soda.’ The example proxy codes  208  of  FIG. 2A  vary in size (e.g., number bits) according to a degree of recent popularity or frequency of occurrence. An example approach of generating the proxy codes  208  of varying sizes based on the frequency of occurrence is described below in connection with  FIGS. 4B and 8 . The phonetic code book  119   a  stores proxy codes  208  in association with phonetic notations. These phonetic notations can be combined to form the approximate pronunciation (e.g., based on sounds and syllable breaks) of virtually any keyword terms (e.g., ‘New York,’ ‘Bubblee,’ and/or ‘soda’) The phonetic breakdown of such terms is described below in connection with  FIGS. 3 ,  5 A, and  5 B. In other example implementations, the code books  119   a  and/or  119   b  are stored in data structures other than those at the central facility  108 . 
     As shown in the example of  FIG. 2A , the encoder  104  uses the proxy codes  208  to construct the content-aware watermark  206 .  FIG. 2B  illustrates a prior art audience measurement code  210 . The prior art watermark  210  includes a source identifier portion  212  having a source identifier  214  and a timestamp portion  216  having a timestamp  218 . The source identifier  214  includes identifying information such as, for example, data corresponding to a call sign (e.g., ABC™) of a broadcasting network. The timestamp  218  includes information indicative of a time at which the encoded watermark  210  is broadcast. The prior art watermark  210  is encoded into or otherwise broadcast with broadcast content and collectible by an audience measurement meter at a downstream location (e.g., a household or business). For example, the prior art watermark  210  may be encoded into the broadcast signal every two and one-half seconds to achieve a high granularity in regards to the collected data. 
     As described above, the approach to transforming the conventional watermark  210  of  FIG. 2A  into a content-aware watermark described in U.S. patent application Ser. No. 12/101,738 reduces the granularity of the conventional audience measurement system by inherently removing information from the conventional watermark  210 . To retain this granularity, the example encoder  104  of  FIG. 2A  either (a) prepends or appends the proxy codes  208  to the source identifier  214  or (b) periodically replaces the source identifier  214  with the proxy codes  208 . Due to the condensed size of the proxy codes  208 , the proxy codes  208  are preferably appended or prepended to the source identifier  214  without an increase in size relative to prior art watermark  210  (e.g., the bandwidth required to encode the content-aware watermark  206 ). To achieve this, the source identifier  214  may be reduced in size (e.g., by using proxy codes to represent the station identifier). 
       FIG. 2C  illustrates a first example content-aware watermark  220  in which the proxy code(s)  208  is prepended to the source identifier  214 . Notably, the size of the source identifier portion  212  remains the same or substantially the same despite the addition of the proxy code(s)  208 . If the proxy codes are small enough, more than one proxy code may be prepended with the same watermark  220 . In a second example content-aware watermark  222  shown in  FIG. 2D , the proxy code(s)  208  are appended to the end of the source identifier  214 . Again, the size of the source identifier portion  212  remains the same or substantially the same despite the addition of the proxy codes  208 . In a third example content-aware watermark  224  shown in  FIG. 2E , the proxy code(s)  208  replace the source identifier  214 . In the third example watermark  224 , the source identifier portion  212  is smaller relative to the conventional watermark  210 , or alternatively, the source identifier portion  212  may remain the same size by packing the source identifier portion  212  with multiple codes and/or with dummy data (e.g., zeros). 
     The watermark configuration  220 ,  224 , or  226  to be used by the content-aware watermark encoder  104  is a design choice. If the proxy code(s)  208  are small enough and/or the source identifier  214  size can be adjusted so as to not affect the size of the source identifier portion  212 , the first or second watermark configuration  220 ,  222  is preferred for the encoding process. Alternatively, if the proxy code(s)  208  are of a size that will affect the size of the source identifier portion  212  and/or the source identifier  214  cannot be reduced to affect the same, the third configuration  224  is preferred for the encoding process. When the third watermark configuration  224  is employed, some loss of granularity will result because the source identifier  214  is eliminated. Therefore, the third type of watermark  224  is periodically used to replace a conventional watermark  210  (e.g., one of every eight watermarks is a content-aware watermark  224 ) to reduce the impact on granularity of the channel change detection. In such an approach, the granularity impact may be reduced to zero or nearly zero because the conventional watermark  210  around the content-aware watermark  224  will indicate channel changes. Further, if different code books are used for different programs and/or channels, the proxy code(s) of the content-aware watermark  224  can be used to infer the channel change by referencing the code books. This approach is particularly useful in the channel surfing context where multiple channels may be tuned over a short period of time. 
     Referring back to  FIG. 2A , a watermark embedder  226  embeds the content-aware watermark  206  (using any of the configurations  220 ,  222 ,  224 ) in one or more frames of the media excerpt  202  using any suitable watermark embedding technique. The watermark embedder  226  can be configured to embed the content-aware watermark  206  in a video portion of the media excerpt  202  and/or an audio portion of the media excerpt  202 . In some example implementations, embedding a watermark  206  in a video domain enables using relatively larger watermarks because of the relatively larger bandwidth available for video than is typically available for audio. In some examples, the example encoding methods, apparatus, and/or articles of manufacture described herein may be used with audio encoding. In other examples, an encoder may be configured to alternate between the representative encoding (e.g., using the proxy codes described herein) and conventional encoding techniques based on the availability of bandwidth and/or what type of content-aware watermark (e.g., audio and/or video) is being employed. For example, when a significant amount of bandwidth is available, keywords may be directly encoded without the use of proxy codes. Alternating encoding techniques is disfavored in view of the attendant decoding difficulties and increased complexities. 
     Although the example implementation of  FIG. 2A  depicts the content-aware watermark encoder  104  as being configured to generate content-aware watermarks based on closed caption text, the content-aware watermark encoder  104  may additionally or alternatively be configured to generate content-aware watermarks based on other features or characteristics of media compositions. For example, the content-aware watermark encoder  104  may additionally or alternatively be configured to generate content-aware watermarks  206  based on a speech-to-text conversion performed on an audio track of a media composition. In other examples, the content-aware watermark encoder  104  may additionally or alternatively be configured to generate content-aware watermarks based on metadata (e.g., title, program name, international standard audiovisual number (ISAN), or any other identifier information), scene changes, blank frames or MPEG splice points, detected logos, etc. Example methods and apparatus to detect logos in the content of media compositions are disclosed in U.S. Provisional Application No. 60/986,723 entitled “Methods and Apparatus to Measure Brand Exposure in Media Streams,” filed on Nov. 9, 2007, which is hereby incorporated by reference herein in its entirety. Example methods and apparatus to detect blank frames are disclosed in U.S. application Ser. No. 11/534,790 entitled “Methods and Apparatus to Detect a Blank Frame in a Digital Video Broadcast Signal,” filed on Sep. 25, 2006, which is hereby incorporated by reference herein in its entirety. 
       FIG. 3  is a block diagram of the example content-aware watermark encoder  104  of  FIGS. 1 and 2 . In the illustrated example of  FIG. 3 , the example content-aware watermark encoder  104  includes a data interface  302 , a closed caption text decoder  304 , a speech-to-text converter  306 , a metadata detector  308 , a media features detector  310 , a word selector  312 , a proxy code inserter  314 , a phonetic converter  316 , a proxy code selector  318 , and a watermark generator  320 . While an example manner of implementing the content-aware watermark encoder  104  of  FIG. 1  has been illustrated in  FIG. 3 , one or more of the elements, processes and/or devices illustrated in  FIG. 3  may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example data interface  302 , the example closed caption text decoder  304 , the example speech-to-text converter  306 , the example metadata detector  308 , the example media features detector  310 , the example word selector  312 , the example proxy code inserter  314 , the example phonetic converter  316 , the example proxy code selector  318 , the example watermark generator  320 , and/or, more generally, the example encoder  104  of  FIG. 3  may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example data interface  302 , the example closed caption text decoder  304 , the example speech-to-text converter  306 , the example metadata detector  308 , the example media features detector  310 , the example word selector  312 , the example proxy code inserter  314 , the example phonetic converter  316 , the example proxy code selector  318 , the example watermark generator  320 , and/or, more generally, the example encoder  104  of  FIG. 3  could be implemented by one or more circuit(s), programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)), etc. When any of the appended claims are read to cover a purely software and/or firmware implementation, at least one of the example data interface  302 , the example closed caption text decoder  304 , the example speech-to-text converter  306 , the example metadata detector  308 , the example media features detector  310 , the example word selector  312 , the example proxy code inserter  314 , the example phonetic converter  316 , the example proxy code selector  318 , the example watermark generator  320 , and/or, more generally, the example encoder  104  of  FIG. 3  are hereby expressly defined to include a tangible medium such as a memory, DVD, CD, etc. storing the software and/or firmware. Further still, the example encoder  104  of  FIG. 3  may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in  FIG. 3 , and/or may include more than one of any or all of the illustrated elements, processes and devices. 
     To transmit and receive data, the example content-aware watermark encoder  104  of  FIG. 3  is provided with the data interface  302 . In the illustrated example, the data interface  302  can be used to receive media composition data (e.g., audio data, video data, etc.), closed caption data, metadata, etc. from media sources (e.g., computer interfaces, cable boxes, televisions, media players, etc.), and communicate information associated with content-aware watermarks to, for example, the watermark embedder  226  ( FIG. 2A ) and/or the proxy code inserter  314 . Further, in the illustrated example, the proxy code selector  318  accesses the appropriate one of the code books  119  ( FIGS. 1 and 2A ) via the data interface  302  to retrieve the proxy codes associated with selected keyword(s) and/or phonetic notation(s) and to provide the retrieved proxy codes to, for example, the proxy code inserter  314 . Although not shown in  FIG. 3 , in some example implementations, the watermark embedder  226  may be implemented as part of the example content-aware watermark encoder  104 . 
     To extract or decode closed caption text from media data received via the data interface  302 , the example content-aware watermark encoder  104  is provided with the closed caption text decoder  304 . In some example implementations, the closed caption text decoder  304  may be omitted from the example content-aware watermark encoder  104  and the content-aware watermark encoder  104  may be configured to receive decoded closed caption text from a closed caption text decoder of a media source coupled to the data interface  302 . 
     To convert speech from media audio tracks to text, the example content-aware watermark encoder  104  is provided with the speech-to-text converter  306 . In the illustrated example, the speech-to-text converter  306  is used to recognize words in media content that does not have closed caption text associated therewith or in situations where closed caption text cannot be obtained (e.g., failure or omission of the closed caption text decoder  304 ). In example implementations in which speech-to-text conversion capabilities are not desired, the speech-to-text converter  306  can be omitted from the example content-aware watermark encoder  104 . 
     To detect metadata in media, the example content-aware watermark encoder  104  is provided with the metadata detector  308 . The metadata detector  308  extracts metadata such as program guide information, universal resource locations (URLs), etc. from the program signal carrying the media composition. 
     In the illustrated example, the example content-aware watermark encoder  104  includes the media features detector  310 . The media features detector  310  is configured to detect particular characteristics or features in media content (e.g., scene changes, blank frames, MPEG splice points, logos, etc.) and to generate metadata descriptive of those characteristics or features. 
     To select words or phrases to form keywords, the example content-aware watermark encoder  104  is provided with the word selector  312 . In the illustrated example, the word selector  312  is configured to select words or phrases indicative or descriptive of respective media content in the metadata, the closed caption text, and/or audio tracks collected by the closed caption text decoder  304 , the speech-to-text converter  306 , the metadata detector  308  and/or the media features detector  310 . To select the words or phrases, the word selector  312  may be configured to use weighted numeric factors or values assigned to pre-identified terms stored in the reference database  118  of  FIG. 1 . In this manner, if multiple terms in the reference database  118  are found in a portion of a media composition, the keywords used in connection with a content-aware watermark for that media composition can be limited to the terms with the highest weights. To reduce the amount of proxy codes, the reference database  118  may use the same proxy code for like terms (e.g., synonyms). To this end, the reference database  118  may include pointers correlating like terms in the database  118 . 
     In some examples, the word selector  312  comprises a list of keywords of interest that are manually input by a system operator and/or obtained from the reference database  118 . When the output of any of the closed caption text decoder  304 , the speech-to-text converter  306 , the metadata detector  308 , and/or the media features detector  310  contains one of the keywords in the list (as detected by a comparator, coded instructions, and/or a logic circuit in the word selector  312 ), the word selector  312  generates an output indicating that a content-aware watermark should be generated, thereby triggering the insertion of a corresponding proxy code into a conventional watermark  210  generated by the watermark generator  320 . When no match is found, the conventional watermark  210  output by the watermark generator  320  is used. 
     In other examples, the watermark generator  320  uses the same structure for the watermarks it outputs in every instance. For example, the watermark generator  320  may always use the format of  FIG. 2C  to generate all watermarks. The watermark generator  320 , thus, always acts in the same manner, namely, generating a watermark having the structure of  FIG. 2C  with the proxy code field  208  populated with zeros, the source identifier field  214  populated with the station identifier of the station broadcasting the media composition in question, and the timestamp field  218  populated with the time and data of the broadcast. In this approach, when the word selector  312  generates an output indicating the need for a content-aware watermark, the proxy code selector  318  obtains and/or creates the required proxy code (e.g., a code for the keyword identified by the word selector  312 ) and the proxy code inserter  314  populates the proxy code field  208  with the corresponding proxy code(s). when the word selector  312  does not generate an output indicating a need for a content-aware watermark, the proxy code selector  318  does nothing and the watermark output by the watermark generator  320  is passed to the data interface  302  for encoding into the media composition without further modification (e.g., with the proxy code field  208  filled with all zeros or other dummy data). 
     To select proxy codes corresponding to keywords and/or phonetic notations for the keywords selected by the word selector  312 , the example content-aware watermark encoder  104  is provided with the proxy code selector  318 . In the illustrated example, the proxy code selector  318  is responsive to the word selector  312  to lookup and/or generate the proxy codes associated with the keyword(s) identified by the word selector  312 . For example, the proxy code selector  318  can access an appropriate keyword code book  119   b  and/or a local copy thereof to retrieve one or more proxy codes corresponding to the keywords selected by the word selector  312 . The proxy code inserter  314  can place the proxy code(s) in the proxy code field  208  of one or more watermarks  220 ,  222 ,  224  output by the watermark generator  320  to form a content-aware watermark  206 . In other examples, the proxy code selector  318  can access a phonetic code book  119   a  to retrieve proxy codes corresponding to one or more phonetic notations that make up the keywords selected by the word selector  312 , and the proxy code inserter  314  can insert the proxy codes into the proxy code field  208  of one or more watermarks  220 ,  222 ,  224  to form a content-aware watermark  206 . 
     In instances where there is no proxy code corresponding to a selected keyword (e.g., when a search of the code book(s)  119  returns no code), the proxy code selector  318  (e.g., in cooperation with the code book  119  as described below in connection with  FIGS. 4B  and  8 ) assigns a new proxy code to the keyword. In some examples, the proxy code selector  318  keeps a running list of used proxy codes and selects a next available code (e.g., the next code in a numeric sequence of codes) to be assigned to the keyword. The keyword and selected proxy code are then sent to an appropriate one of the code books  119  (e.g., via the data interface  302 ). A similar approach is used by the proxy code selector  318  in examples where a code book is created on a program by program or channel by channel basis. In such examples, the proxy code may be universally unique (e.g., across all code books), or locally unique (e.g., within the corresponding code book). 
     As mentioned above, the example encoder  104  of  FIG. 3  includes a proxy code inserter  314 . The proxy code inserter  314  inserts the proxy code retrieved by or selected by the proxy code selector  318  into the proxy code field(s)  208  of the watermark output by the watermark generator  320  to create a content-aware watermark. If there are too many proxy codes (e.g., where multiple codes are used to identify a keyword or multiple keywords are to be encoded), the proxy code inserter  314  spreads the codes across multiple watermarks and inserts an indication to identify the start and/or stop of a series of codes. The indication(s) may be proxy code(s) that are reserved for purposes of identifying the start and stop to the decoder. 
     To phonetically represent the keyword(s), the example content-aware watermark encoder  104  is provided with the phonetic converter  316 . The phonetic converter  316  converts words into one or more representations of the approximate pronunciation of the words. The phonetic notations are chosen from a collection or library of phonetic notations, such as the International Phonetic Alphabet (IPA), which is a system of phonetic notation devised by the International Phonetic Association and based on the Latin alphabet. The IPA can be used to represent words of any language. However, the algorithms of the phonetic converter  316  may be optimized to operate on one language or a subset of languages likely to be encountered by the phonetic converter  316  (e.g., based on a geographic location of installation and/or service). 
     Additionally, the phonetic converter  316  delineates points at which phonetic notations (or the proxy codes associated therewith) corresponding to one keyword end and points at which phonetic notations (or the proxy codes associated therewith) corresponding to another keyword begin. In other words, the phonetic converter  316  is capable of defining when a new term or phrase begins. The phonetic converter  316  passes the phonetic notation and the indication of the start and stop of the keywords to the proxy code selector  318 . The proxy code selector  318  then looks up the proxy code(s) corresponding to the phonetic notations in a phonetic code book  119   a  and passes the proxy codes and the start and stop indication to the proxy code inserter  314 . The proxy code inserter  314  then enters a proxy code for the start indication, a proxy code for the stop indications, and proxy code(s) for the phonetic notations into the proxy code fields of one or more watermarks as explained above. As noted above, the proxy code inserter  314  inserts a proxy codes as markers in between the proxy code representing a first keyword and the proxy code representing a second keyword to enable the decoder  114  to properly translate the keywords. In some examples, no proxy code is required. 
       FIG. 4A  illustrates the example content-aware watermark decoder  114  of  FIG. 1  shown in communication with the example central facility  108  of  FIG. 1 . In the illustrated example, the example content-aware watermark decoder  114  includes a media interface  402 , a watermark detector  404 , a data extractor  406 , a signature generator  408 , a data interface  410 , a timestamp generator  412 , and a proxy code translator  414 . While an example manner of implementing the content-aware watermark decoder  114  of  FIG. 1  has been illustrated in  FIG. 4A , one or more of the elements, processes and/or devices illustrated in  FIG. 4A  may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example media interface  402 , the example watermark detector  404 , the example data extractor  406 , the example signature generator  408 , the example data interface  410 , the example timestamp generator  412 , the example proxy code translator  414 , and/or, more generally, the example decoder  114  of  FIG. 4A  may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example media interface  402 , the example watermark detector  404 , the example data extractor  406 , the example signature generator  408 , the example data interface  410 , the example timestamp generator  412 , the example proxy code translator  414 , and/or, more generally, the example decoder  114  of  FIG. 4A  could be implemented by one or more circuit(s), programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)), etc. When any of the appended claims are read to cover a purely software and/or firmware implementation, at least one of the example media interface  402 , the example watermark detector  404 , the example data extractor  406 , the example signature generator  408 , the example data interface  410 , the example timestamp generator  412 , the example proxy code translator  414 , and/or, more generally, the example decoder  114  of  FIG. 4A  are hereby expressly defined to include a tangible medium such as a memory, DVD, CD, etc. storing the software and/or firmware. Further still, the example decoder  114  of  FIG. 4A  may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in  FIG. 4A , and/or may include more than one of any or all of the illustrated elements, processes and devices. 
     To receive audio and/or video media, the example content-aware watermark decoder  114  is provided with the media interface  402 . To detect watermarks (e.g., the content-aware watermark  206  of  FIG. 2A ) in the media received via the media interface  402 , the example content-aware watermark decoder  114  is provided with the watermark detector  404 . The content-aware watermarks detected by the watermark detector  404  may be media feature based (e.g., identifying blank frames, scene changes, etc.) and/or keyword based (e.g., representing content of the media program). 
     To extract proxy code(s) from the detected content-aware watermarks, the example content-aware watermark decoder  114  is provided with the data extractor  406 . For example, the data extractor  406  extracts the proxy codes (e.g., binary or hexadecimal words) corresponding to the keywords ‘New York,’ ‘Bubblee,’ and/or ‘soda’ from the content-aware watermark  206  described above in connection with  FIG. 2A . Additionally or alternatively, in the illustrated example, the data extractor  406  extracts proxy codes (e.g., binary or hexadecimal words) corresponding to one or more phonetic notations that collectively represent one or more keywords. For example, with respect to the term ‘soda’ from the content-aware watermark  206  described above in connection with  FIG. 2A , the data extractor  406  extracts a proxy code corresponding to the phonetic notation representative of the first syllable of ‘soda’ (e.g., ‘soh’) and another proxy code corresponding to the phonetic notation representative of the second syllable of ‘soda’ (e.g., ‘duh’). As described above, the phonetic notations are chosen from a collection or library of phonetic notations, such as the International Phonetic Alphabet (IPA). The data extractor  406  also extracts proxy codes delineating the start and/or stop of a keyword, if present. 
     For the purpose of converting proxy codes extracted by the data extractor  406  into the keywords or phonetic notations they represent, the decoder  114  is provided with the proxy code translator  414 . The proxy code translator  414  access the appropriate code book(s)  119  and uses the proxy code(s) to lookup the keywords and/or phonetic notations. The code book(s)  119  may be local (e.g., within the decoder  114 ) or remote (e.g., at the central facility  108  as shown in  FIG. 4A ). Although the proxy code translator  414  is shown as present in the decoder  114 , it could alternatively be located at the central facility  108 . When the proxy code translator  414  is located at the decoder  114 , it is preferred to maintain local copies of the code book(s)  119  at the decoder  114 . 
     To transmit and receive data, the example content-aware watermark decoder  114  is provided with the data interface  410 . In the illustrated example, the data interface  410  can be used to store the keyword(s), proxy code(s), and/or signature(s) (e.g., as generated by the signature generator  408  discussed below) in a memory and/or to communicate the same to the central facility  108 . Further, the example data interface  410  of  FIG. 4A  has access to the code book(s)  119  ( FIGS. 1 and 2 ) at the central facility  108  to obtain keyword(s) and/or phonetic notations associated with extracted proxy codes. 
     In the illustrated example, for the purpose of reconstructing keywords from phonetic notations, the central facility  108  is provided with the phonetic converter  120 . In alternative examples, the phonetic converter  120  is located at the decoder  114 . Irrespective of its location, the phonetic converter  120  converts the phonetic notations retrieved via the proxy code lookup performed by the proxy code translator  414  into the corresponding keyword(s). The resulting keyword(s) constitute the content-descriptive information that was encoded into the content-aware watermark by the content-aware watermark encoder  104  ( FIGS. 1-3 ) and are, thus, stored for further processing. 
     As described above, the example central facility  108  of  FIG. 1  includes a plurality of code books  119 . In some examples, each television program is assigned an individual code book containing proxy codes associated with, for example, characters names in a code book assigned to a sitcom, celebrity names in a code book assigned to an entertainment program, or current event titles in a code book assigned to a news program or talk show. In such instances, the source identifiers (e.g., the source identifier  214  of  FIG. 2B ) and timestamps (e.g., the timestamp  218  of  FIG. 2B ) can be used to identify which code book should be referenced when correlating the proxy codes with the keyword(s) stored therein. For example, when a source identifier  214  corresponding to “News Show XYZ” is received, the decoder  104  assigned the task of correlating the proxy codes with the corresponding keywords knows to access the code book assigned to “News Show XYZ” based on the source identifier. 
     In examples employing the watermark structure  224  of  FIG. 2E , no source identifier  214  is present in the content-aware watermark  224 . In such examples, the content-aware watermarks  224  are interleaved with conventional watermarks  210  (see  FIG. 2B ) and, thus, the source identifier  214  from the conventional watermarks  210  surrounding the content-aware watermarks  224  may be used by the decoder  114  to identify the correct one of the code books  119 . In the event that the source identifier  214  from a conventional watermark  210  proceeding a content-aware watermark  224  does not match the source identifier  214  from the conventional watermark  210  following the content-aware watermark  224 , a channel change event has occurred and it may not be possible to credit the content represented by the content-aware watermark  224  unless the code book associated with the first source identifier and the code book associated with the second source identifier do not both use the proxy code. If only one of the two code books include the cod, the content can be credited since it is implicitly known which station was tuned. 
     In some examples, rather than assigning a specific code book to each program, a specific code book is assigned to each station. The above examples explaining the use of the code books in the program based code book context apply with equal force to the code books assigned to station context. 
     In the illustrated example, the content-aware watermark decoder  114  is also provided with a signature generator  408  to generate signatures of audio and/or video portions of the media received via the media interface  402 . In some example implementations, the signatures can be compared to reference signatures stored in, for example, the reference database  118  of  FIG. 1  in association with media composition identification information to identify the media compositions presented to audience members. 
     Further, in the illustrated example, the timestamp generator  412  is configured to generate timestamps indicating the date and/or time(s) at which (1) the proxy code(s) are recovered from a media composition by the content-aware watermark decoder  114  and/or (2) signature(s) are generated by the signature generator  412 . The timestamps may be representative of a time of day to indicate when an audience member was exposed to media content represented by the proxy code(s) or the signatures. Alternatively or additionally, the timestamps may be representative of a track time or elapsed media presentation time of the media composition to indicate the temporal location in the media composition from where the watermark(s) containing the proxy code(s) associated with the keyword(s) were extracted or the signature(s) were generated. 
       FIG. 4B  is a block diagram of an example apparatus  415  that may be used to generate the example code book(s)  119  of  FIGS. 1 and 4A . In particular, the example apparatus  415  is a code book generator  415  which is configured to associate proxy codes with keywords and/or portions of keywords occurring in media compositions. varying in size according to a frequency of occurrence in a set of media compositions. The set of media compositions may correspond to a group of programs broadcast on a certain set of channels over a certain period of time (e.g., the previous two weeks or one month). The determination of which channels and/or what periods of time are to constitute the set of media compositions is a design choice to be made by, for example, a media exposure measurement entity. In the illustrated example, keywords (and/or portions thereof) occurring more frequently in the set of media compositions are assigned smaller proxy codes such that the most commonly used proxy codes take up a reduced amount of bandwidth compared to the larger proxy codes assigned to less frequently occurring keywords (and/or portions thereof). 
     To determine which keywords (and/or portions thereof) are to be assigned proxy codes, the example code book generator  415  of  FIG. 4B  includes a word identifier  416 . In the illustrated example, the word identifier  416  accesses the reference database  118  to obtain a list of keywords of interest as entered by, for example, a system operator. In other examples, the word identifier  416  may access any other suitable source to determine which words are likely to be selected as content-descriptive information (e.g., by the word selector  312  of the encoder  104 ). 
     To determine how often the keywords identified by the word identifier  416  occur in the set of media compositions, the example code book generator  415  of  FIG. 4B  includes a frequency calculator  418  and a media composition parser  420 . In the illustrated example, the code book generator  415  receives the set of media compositions via a data interface  422  and stores a temporary copy of the same in a memory  424 . The media composition parser  420  searches the media compositions for instances of the words identified by the word identifier  416 . For example, the media composition parser  420  of  FIG. 4B  performs a comparison of the words identified by the word identifier  416  and a closed caption text conveyed to the code book generator  415  in association with the set of media compositions. 
     The number of instances of each word of interest is conveyed to the frequency calculator  418 . In the illustrated example, the frequency calculator  418  assigns a frequency of occurrence to each word based on the corresponding number of occurrences and the number of media content compositions contained in the set of media compositions. In particular, the example frequency calculator  418  computes a frequency percentage in accordance with the following equation: 
     
       
         
           
             
               
                 
                   
                     frequency 
                     = 
                     
                       
                         # 
                          
                         
                             
                         
                          
                         of 
                          
                         
                             
                         
                          
                         occurences 
                       
                       
                         # 
                          
                         
                             
                         
                          
                         of 
                          
                         
                             
                         
                          
                         programs 
                       
                     
                   
                   , 
                   . 
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
     The example frequency calculator  418  of  FIG. 4B  groups the frequency values into ranges and assigns values to each range of frequency percentage. For example, a first word with a frequency percentage of one percent may be assigned the same frequency value by the frequency calculator as a second word with a frequency percentage of two percent. In other examples, the frequency calculator  418  may simply use the frequency percentage as the frequency value. 
     The frequency value assigned to each word by the frequency calculator  418  is conveyed to a proxy code selector  426 . The proxy code selector  426  includes and/or has access to a set of proxy codes (e.g., a numeric sequence of codes) that are available to be assigned to the keywords. In the illustrated example, the set of available proxy codes includes proxy codes of varying sizes. As described above, inserting one or more proxy codes into a conventional watermark (e.g., for the purpose of transforming the conventional watermark into a content-aware watermark) may impact the granularity of the associated information (e.g., station identification information). Accordingly, the example code book generator  415  of  FIG. 4B  assigns the smaller of the available proxy codes to the most frequently occurring words. Specifically, the proxy code selector  426  determines which of the words identified by the word identifier  416  were assigned the highest frequency value and/or fall within the highest frequency value range. These words are then associated with the smallest available proxy codes by the proxy code selector  426 . The proxy selector then determines which of the words identified by the word identifier  416  were assigned the next highest frequency value and/or fall within the next highest frequency value range. These words are then associated with the next smallest available proxy codes by the proxy code selector  426 . In the illustrated example, this process continues until each word identified by the word identifier  416  is associated with a proxy code. The words identified by the word identifier  416 , along with the associated proxy codes, are then stored in the memory  424  as a code book  119 . 
     In an alternative implementation, the example code book generator  415  may assign proxy codes to a plurality of keywords using a different approach. In particular, the code book generator  415  may initially use the media composition parser  420  to parse through a set of media compositions and to calculate a number of occurrences for the words present in the media compositions. For example, the media composition parser  420  may receive the set of media compositions from the data interface  422  and determine that a first word occurs one thousand times, that a second word occurs eight hundred times, that a third word occurs seven hundred times, etc. In such instances, the word identifier  416  then identifies the keywords to be assigned proxy codes based on the calculations made by the media composition parser  420 . For example, the word identifier  416  may identify the most frequently occurring three hundred nouns found in the media compositions as the keywords to be assigned proxy codes. 
     Similar to the example described above, the number of occurrences of each word identified by the word identifier  416  is conveyed to the frequency calculator  418 . Further, the frequency calculator  418  assigns a frequency of occurrence to each word based on the corresponding number of occurrences and the number of media content compositions contained in the set of media compositions (e.g., using equation 1 listed above). The frequency value assigned to each word by the frequency calculator  418  is conveyed to a proxy code selector  426 , which associates a proxy code with the identified keywords as described above. The words identified by the word identifier  416 , along with the associated proxy codes, are then stored in the memory  424  as a code book  119 . 
     While an example manner of implementing the code book generator  415  has been illustrated in  FIG. 4B , one or more of the elements, processes and/or devices illustrated in  FIG. 4B  may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example word identifier  416 , the example frequency calculator  418 , the example media composition parser  420 , the example data interface  422 , the example memory  424 , the example proxy code selector  426 , and/or, more generally, the example code book generator  415  of  FIG. 4B  may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example word identifier  416 , the example frequency calculator  418 , the example media composition parser  420 , the example data interface  422 , the example memory  424 , the example proxy code selector  426 , and/or, more generally, the example code book generator  415  of  FIG. 4B  could be implemented by one or more circuit(s), programmable processor(s), application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)), etc. When any of the appended claims are read to cover a purely software and/or firmware implementation, at least one of the example word identifier, the example frequency calculator, the example media composition parser, the example data interface, the example memory, the example proxy code selector, and/or, more generally, the example code book generator are hereby expressly defined to include a tangible medium such as a memory, DVD, CD, etc. storing the software and/or firmware. Further still, the example code book generator  415  of  FIG. 4B  may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in  FIG. 4B , and/or may include more than one of any or all of the illustrated elements, processes and devices. 
     The flow diagrams depicted in  FIGS. 5A ,  5 B, and  6 - 8  are representative of machine readable instructions that can be executed to implement the example systems, methods, apparatus, and/or articles of manufacture described herein. In particular,  FIGS. 5A and 5B  depict a flow diagram representative of machine readable instructions that may be executed to implement the example content-aware watermark encoder  104  of  FIGS. 1-3  to construct content-aware watermarks and embed the content-aware watermarks into media.  FIG. 6  is a flow diagram representative of machine readable instructions that may be executed to implement the example content-aware watermark decoder  114  of  FIGS. 1 and 4A  to detect, decode, and transmit information associated with content-aware watermarks.  FIG. 7  is a flow diagram representative of example machine readable instructions that may be executed to implement the example central facility  108  of  FIGS. 1 and 4A  to process information received from the example decoder of  FIGS. 1 and 4A .  FIG. 8  is a flow diagram representative of example machine readable instructions that may be executed to implement the example code book(s)  119  of  FIGS. 1 ,  4 A, and/or  4 B to select one or more proxy codes for one or more keywords. 
     The example processes of  FIGS. 5A ,  5 B, and  6 - 8  may be performed using a processor, a controller and/or any other suitable processing device. For example, the example processes of  FIGS. 5A ,  5 B, and  6 - 8  may be implemented in coded instructions stored on a tangible medium such as a flash memory, a read-only memory (ROM) and/or random-access memory (RAM) associated with a processor (e.g., the example processor  912  discussed below in connection with  FIG. 9 ). Alternatively, some or all of the example processes of  FIGS. 5A ,  5 B, and  6 - 8  may be implemented using any combination(s) of application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)), field programmable logic device(s) (FPLD(s)), discrete logic, hardware, firmware, etc. Also, some or all of the example processes of  FIGS. 5A ,  5 B, and  6 - 8  may be implemented manually or as any combination(s) of any of the foregoing techniques, for example, any combination of firmware, software, discrete logic and/or hardware. Further, although the example processes of  FIGS. 5A ,  5 B, and  6 - 8  are described with reference to the flow diagrams of  FIGS. 5A ,  5 B, and  6 - 8 , other methods of implementing the processes of  FIGS. 5A ,  5 B, and  6 - 8  may be employed. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, sub-divided, or combined. Additionally, any or all of the example processes of  FIGS. 5A ,  5 B, and  6 - 8  may be performed sequentially and/or in parallel by, for example, separate processing threads, processors, devices, discrete logic, circuits, etc. 
     Turning to  FIG. 5A , initially the data interface  302  ( FIG. 3 ) receives media composition data (block  502 ) from, for example, a media source. The word selector  312  then selects a portion of the media data to process for generating a content-aware watermark and the watermark generator  320  generates a watermark using one of the watermark configurations  220 ,  222 ,  224  of  FIG. 2C ,  2 D, or  2 E (block  504 ). The watermark generator  320  populates the source identifier field  214  and the timestamp field  218  with appropriate data and fills the proxy code field  208  with dummy data (block  504 ). The content-aware watermark encoder  104  ( FIGS. 1 and 2A ) then determines whether it should create audio track-based keyword(s) (block  506 ). For example, if a user and/or administrator sets a configuration option of the content-aware watermark encoder  104  to not generate audio track-based keyword(s), if an audio track and/or closed caption text is not present, or if a user sets a configuration option to only generate metadata-based keyword(s), the content-aware watermark encoder  104  will determine that it should not create audio track-based keywords (block  506 ) and control will advance to block  518 . 
     If the example content-aware watermark encoder  104  determines that it should create audio track-based keyword(s) (block  506 ), the media features detector  310  ( FIG. 3 ) determines whether the media data portion includes closed caption text (block  508 ). If the media data portion includes closed caption text (block  508 ), the closed caption text decoder  304  ( FIG. 3 ) retrieves the closed caption text (block  510 ) from the media data such as, for example, the closed caption text  204  of  FIG. 2A . 
     If the media data portion does not include closed caption text (block  508 ), the speech-to-text converter  306  ( FIG. 3 ) retrieves the audio track portion from the media data portion (block  512 ). The speech-to-text converter  306  then performs a speech-to-text conversion (block  514 ) on the audio track portion to generate a textual representation of the audio track portion. After performing the speech-to-text conversion (block  514 ) or after retrieving the closed caption text (block  510 ), the word selector  312  ( FIG. 3 ) selects one or more keyword(s) (block  516 ) from the closed caption text retrieved at block  510  and/or the text generated at block  514 . For example, to select the keyword(s), the word selector  312  may select words or phrases in the closed caption text or audio track portion indicative or descriptive of content in the media data portion and/or mentioned or presented in the media data portion, such as capitalized words in the closed caption text. Additionally or alternatively, the word selector  312  may be configured to select words or phrases that might be of interest to a user searching for media content in, for example, servers coupled to the Internet (e.g., the media servers  102   a - c  coupled to the internetwork  112  of  FIG. 1 ). The keywords may be selected by, for example, comparing words detected in the closed caption text or audio track portion to words of interest identified in a list in, for example, the reference database  118  ( FIG. 1 ) (e.g., ‘New York’ may be pre-identified as a term of interest to be selected when found). The pre-selected keywords in the reference database  118  may be weighted with a numeric factor so if multiple terms in the reference database  118  are found in a portion of a media composition, the keywords encoded into content-aware watermarks can be limited to the terms with the highest weights. 
     After the word selector  312  selects the keyword(s) at block  516 , or if the content-aware watermark encoder  104  determined that it should not create audio track-based keywords (block  506 ), the example content-aware watermark encoder  104  then determines whether it should create metadata-based keyword(s) (block  518 ). For example, if a user sets a configuration option of the content-aware watermark encoder  104  to not generate metadata-based keyword(s) or if a user and/or administrator sets a configuration option to only generate audio track-based keyword(s), the content-aware watermark encoder  104  will determine that it should not create metadata-based keywords (block  518 ) and control will advance to block  530  ( FIG. 5B ). 
     If the example content-aware watermark encoder  104  determines that it should create metadata-based keyword(s) (block  518 ) (e.g., the content-aware watermark encoder is configured to create metadata-based keyword(s)), the metadata detector  308  ( FIG. 3 ) determines whether metadata is present in the media data portion (block  520 ). If metadata is present, the metadata detector  308  retrieves the metadata from the media data portion (block  522 ). 
     If metadata is not present in the media data portion (block  520 ), the media features detector  310  ( FIG. 3 ), detects media features (or characteristics) in the media data portion (block  524 ). For example, the media features detector  310  may detect media features specified in, for example, configuration settings of the content-aware watermark encoder  104 . If the configuration settings specify that content-aware watermarks should include keywords indicative of blank frames, the media features detector  310  detects blank frames in the media portion at block  524 . The media features detector  310  then generates keywords based on the features (or characteristics) detected at block  524 . 
     After the media features detector  310  generates keywords based on the detected features (or characteristics) (block  524 ) or after the metadata detector  308  retrieves the metadata from the media data portion (block  522 ), the word selector  312  ( FIG. 3 ) selects (or creates) one or more of the keyword(s) for inclusion (block  528 ). For example, a keyword for a blank frame may be written as a keyword ‘BF012032’ indicating a blank frame at timestamp 1:20:32. A content aware watermark could be embedded in the corresponding blank frame or in a frame preceding or following the blank frame. As with the keywords for the audio portion of the content, keywords indicative of metadata or media features may be selected by referencing the reference database  118  storing preselected, weighted terms of contents. 
     After the keyword(s) are selected (or created) (block  528 ) or if the content-aware watermark encoder  104  determines that it should not create keywords based on metadata or media features (block  518 ), the content-aware watermark encoder  104  determines whether keyword(s) have been selected (or created) (block  530 ) ( FIG. 5B ). For example, if the content-aware watermark encoder  104  determined that it should not create audio track-based keyword(s) (block  506 ) and determined that it should not create metadata or media feature based keyword(s) (block  518 ), the content-aware watermark encoder  104  determines that no keyword(s) have been selected (or created) (block  530 ) and control advances to block  542 . 
     Otherwise, if keyword(s) have been selected (or created) (block  530 ), the content-aware watermark encoder  104  determines whether the keyword(s) are to be phonetically encoded (block  532 ). For example, the content-aware watermark encoder  104  may be configured to break down or convert the keyword(s) into phonetic notations representative of their approximate pronunciation. In the illustrated example, to determine whether to phonetically encode the keyword(s), the content-aware watermark encoder  104  checks an internal setting that determines a mode of operation. In some instances, one or more administrators of the media network system  100  and/or any of the components thereof (e.g., the content-aware watermark encoders  104 ) are charged with setting and/or changing the internal setting based on, for example, desired performance characteristics, current capabilities, and/or the size of the selected keyword(s) and/or the associated proxy codes. 
     In other examples, the content-aware watermark encoder  104  may first attempt to retrieve a proxy code associated with the keyword(s) from the code book  119  via the data interface  302  and, after finding that no such proxy code is stored in the code book  119 , determine that the keyword(s) are to be phonetically encoded. In other words, instructions to phonetically encode the keyword(s) may result from either (1) a lack of a proxy code associated selected keyword(s) or (2) the internal setting described above. Such a configuration may account for instances in which the word selector  312  inaccurately chose the keyword(s) (e.g., based on a set of desirable keywords stored in the reference database  118 ) or when the word selector  312  chose a keyword not yet encountered or indexed in the set of proxy codes. 
     If the content-aware watermark encoder  104  determines that keyword(s) are to be phonetically encoded (block  532 ), the phonetic converter  316  ( FIG. 3 ) converts the keyword(s) into one or representations of the approximate pronunciation of the keyword(s) (block  534 ) and sets an indicator (e.g., a status bit) associated with the resulting representations of the of the keyword(s) to indicate that the phonetic conversion has occurred. As described above in connection with  FIG. 3 , to perform such a conversion, the example phonetic converter  316  of  FIG. 3  employs one or more algorithms to divide words into one or more phonetic notations. 
     After the phonetic notations are generated (block  534 ) or when the keyword(s) are not to be phonetically encoded (block  532 ), the proxy code selector  318  ( FIG. 3 ) accesses the appropriate code book  119  ( FIG. 2A ) to retrieve proxy codes (block  536 ) corresponding to the keyword(s) and/or the phonetic notations representative of the keyword(s) selected at block  516  and/or block  528  of  FIG. 5A . The indicator set (or not set) at block  534  is referenced by the proxy code detector  318  to determine whether a phonetic conversion has occurred and, thus, the code book  119  mapping proxy codes to phonetic notations must be accessed, or whether proxy code(s) directly associated with the keyword(s) are to be retrieved. In the illustrated example, the size of the retrieved proxy codes depends on a frequency at which the proxy codes are chosen. That is, more popular keywords are assigned smaller proxy codes. Similarly, when building the phonetic code book  119   a,  smaller proxy codes are preferably assigned to the most commonly used phonetic notations. 
     After the proxy code(s) are returned (or should have been returned) from the code book (block  536 ), the proxy code selector  318  determines whether all required proxy codes have been returned (block  537 ). If not all required codes are returned (e.g., there is no proxy code in the code book(s) for a given keyword) (block  537 ), the proxy code selector  318  assigns a new proxy code to the keyword and writes the new keyword-proxy code pair in the appropriate code book (block  538 ). 
     After the proxy code(s) are retrieved (block  536 ), the proxy code inserter  314  ( FIG. 3 ) inserts the proxy code(s) in the proxy code field  208  of the watermark created at block  504  to create a content-aware watermark (e.g., the content aware watermark  206  of  FIG. 2A ) (block  539 ). As described above in connection with  FIG. 2C-2E , the proxy code(s) are inserted into a proxy code field  208  that is prepended or appended to the source identifier field  214  or in place of the source identifier  214 . The watermark embedder  226  ( FIG. 2A ) then embeds or otherwise associates the content-aware watermark with the media composition (block  540 ). For example, the watermark embedder  226  can embed the content-aware watermark in the media data portion selected at block  504  and/or in any portion of the media signal. 
     After the watermark embedder  226  embeds the content-aware watermark in the media composition (block  540 ) or if keyword(s) have not been selected (or created) (block  530 ), the content-aware watermark encoder  104  determines whether it should select another media data portion (block  542 ) for which to generate a content-aware watermark. In the illustrated example, if the content-aware watermark encoder  104  has not processed all of the media composition received at block  502 , the word selector  312  ( FIG. 3 ) selects another media data portion (block  544 ) and control returns to block  506  of  FIG. 5A  for further processing as explained above. Otherwise, if the content-aware watermark encoder  104  determines that it should not select another media data portion (e.g., the content-aware watermark encoder  104  has processed all of the media composition received at block  502  or a configuration setting of the content-aware watermark encoder  104  specifies to only generate content-aware watermarks for a particular portion of media compositions (e.g., the starting portion or the ending portion)) (block  542 ), the data interface  302  passes the media composition data including the content-aware watermark to a transmitter for broadcast or stores the media composition in a data store (e.g., one of the media servers  102   a - e  of  FIG. 1 ) for later broadcast (block  546 ). The example process of  FIGS. 5A and 5B  then terminates. 
       FIG. 6  illustrates example instructions that may be executed to implement the decoder  114  to detect, decode, and transmit information associated with content-aware watermarks. Initially, the media interface  402  ( FIG. 4A ) of the content-aware watermark decoder  114  receives a media composition (block  602 ) having one or more embedded content-aware watermarks. For example, the media interface  402  can receive a media composition from the personal computer  110  or the television  122  of  FIG. 1 . The watermark detector  404  ( FIG. 4A ) detects one or more content-aware watermark(s) (block  604 ) from the media composition data. The data extractor  406  ( FIG. 4A ) retrieves one or more proxy code(s) from the content-aware watermark(s) (block  606 ). 
     Then, the content-aware watermark decoder  114  determines whether it should generate any signatures (block  608 ). For example, the content-aware watermark decoder  114  may have configuration settings specifying that it should generate signatures when a code cannot be read. If the content-aware watermark decoder  114  determines that it should generate one or more signature(s) (block  608 ), the signature generator  408  ( FIG. 4A ) generates the signature(s) (block  610 ). 
     After the signature generator  408  generates the signature(s) (block  610 ) or if the example content-aware watermark decoder  114  determines that it should not generate any signatures (block  608 ), the timestamp generator  412  ( FIG. 4A ) of the content-aware decoder  114  generates one or more timestamp(s) (block  612 ) indicating the date and/or time at which the proxy code(s) were extracted and/or the signature(s) were generated. Typically, the timestamping is done at the monitored media site. 
     The proxy code(s), timestamp(s), and/or signature(s) are stored in a memory (block  614 ) such as, for example, the memory  924  or the memory  925  of  FIG. 9 . In systems that employ a people meter or other mechanism for identifying the audience member, the identity and/or demographic characteristics of the audience member(s) that were exposed to the media content represented by the keyword(s) are also stored. Typically, the demographic data collection is done at the monitored media site. 
     The proxy code translator  414  then translates any proxy codes extracted by the data extractor  404  into keyword(s) and/or phonetic notations (block  615 ). The proxy code translator  414  performs this translation by looking up the proxy code(s) in the corresponding code book(s). 
     The content-aware watermark decoder  114  then communicates the content-descriptive information (e.g., proxy code(s) and/or keyword(s) and/or phonetic notations), timestamp(s), and/or signature(s), or any other information related to the content-aware watermark(s), to the central facility  108  (block  616 ). For example, the data interface  410  can send information to a communication interface (not shown) communicatively coupled to the central facility  108  via, for example, a network connection (e.g., the Internet), a telephone connection, etc. The example process of  FIG. 6  then terminates. 
       FIG. 7  illustrates example instructions that may be executed to implement the central facility  108  to process information received from the decoder  114  associated with content-aware watermarks. Initially, the central facility  108  receives the content-descriptive information from the decoder  114  (as communicated at block  616  of  FIG. 6 ) (block  700 ). The central facility  108  then determines whether a phonetic conversion is needed (block  702 ) by, for example, checking the indicator described above in connection with block  534  of  FIG. 5B . In the illustrated example, the indicator is transferred from the decoder  114  with the content-descriptive data and indicates whether a phonetic conversion has occurred (e.g., during an encoding of the keywords into a content-aware watermark). If a phonetic conversion is needed, the phonetic converter  120  references the phonetic code book  119   a  to obtain the phonetic notations corresponding to the received proxy codes. The phonetic converter  120  then uses the phonetic notations to reassemble one or more keywords (block  704 ). The keywords, which describe the content of the audio/video programming exposed to the corresponding audience, is then conveyed to the example analysis server  116  of  FIG. 1 , which can use such information to develop ratings and/or perform other analyses (block  706 ). The example process of  FIG. 7  then terminates. 
       FIG. 8  is a flow diagram representative of example machine readable instructions that may be executed to implement the example code book generator  415  of  FIG. 4B  to associate one or more proxy codes with one or more keywords. As described herein, the example code book generator  415  of  FIG. 4B  is configured to associate proxy codes with keywords to form a code book  119 . In the illustrated example, keywords occurring more frequently in a certain group of media compositions (e.g., broadcast on one or more broadcast channels) over in certain period of time (e.g., as determined by a media exposure measurement entity) are assigned smaller proxy codes such that the most commonly used proxy codes take up a reduced amount of bandwidth compared to the larger proxy codes assigned to less frequently occurring keywords. 
     Initially, the example word identifier  416  ( FIG. 4B ) determines which words are to be assigned proxy codes (block  800 ). In the illustrated example, the word identifier  416  accesses the reference database  118  to obtain a list of keywords of interest as entered by, for example, a system operator. In other examples, the word identifier  416  may access any other suitable source to determine which words are to be selected as content-descriptive information. The code book generator  415  then receives, via the example data interface  422  ( FIG. 4B ), the set of media compositions for which the frequency of occurrence of the identified words is to be measured (block  802 ). 
     The example media composition parser  420  ( FIG. 4B ) searches the media compositions for instances of the words identified by the word identifier  416  and maintains a tally of the number of identified instances of each word (block  804 ). In the illustrated example, parsing through the set of media compositions includes performing a comparison of the words identified by the word identifier  416  and a closed caption text conveyed to the code book  119  in association with the set of media compositions. In other examples, the content of the media compositions may be alternatively identified and compared to the words identified by the word identifier  416 . 
     The number of instances of each word of interest is conveyed to the example frequency calculator  418  ( FIG. 4B ). In the illustrated example, the frequency calculator  418  assigns a frequency of occurrence to each word based on the corresponding number of occurrences and the amount of media content contained in the set of media compositions (block  806 ). In particular, the example frequency calculator  418  assigns values to each word according to a range of frequencies. For example, a first word occurring one percent of the time covered by the set of media compositions may be assigned the same frequency value by the frequency calculator as a second word occurring two percent of the time covered by the set of media compositions. In other examples, the frequency calculator  418  may assign a frequency value to each occurring word without regard to any frequency range. 
     The frequency value assigned to each word by the frequency calculator  418  is conveyed to a proxy code selector  426  ( FIG. 4B ), which includes and/or has access to a set of proxy codes of varying sizes that are available to be assigned to the words identified at block  800 . The proxy code selector  426  determines which of the remaining (e.g., not yet associated with a proxy code) words identified by the word identifier  416  were assigned the highest frequency value and/or fall within the highest frequency value range. These words are then associated with the smallest available proxy codes by the proxy code selector  426  (block  808 ). The words identified by the word identifier  416 , along with the associated proxy codes, are then stored in the memory  424  (block  810 ) as a code book  119 . The proxy selector then determines if all of the words identified by the word identifier  416  have been assigned proxy code (block  812 ). If each of the identified words has been assigned a proxy code, the process of  FIG. 8  terminates. Otherwise, control passes back to block  808 , where the remaining word having the highest assigned frequency value is associated with the smallest available proxy code. 
       FIG. 9  is a block diagram of an example processor system  910  that may be used to implement the apparatus and methods described herein. As shown in  FIG. 9 , the processor system  910  includes a processor  912  that is coupled to an interconnection bus  914 . The processor  912  may be any suitable processor, processing unit or microprocessor. Although not shown in  FIG. 9 , the system  910  may be a multi-processor system and, thus, may include one or more additional processors that are identical or similar to the processor  912  and that are communicatively coupled to the interconnection bus  914 . 
     The processor  912  of  FIG. 9  is coupled to a chipset  918 , which includes a memory controller  920  and an input/output (I/O) controller  922 . As is well known, a chipset typically provides I/O and memory management functions as well as a plurality of general purpose and/or special purpose registers, timers, etc. that are accessible or used by one or more processors coupled to the chipset  918 . The memory controller  920  performs functions that enable the processor  912  (or processors if there are multiple processors) to access a system memory  924  and a mass storage memory  925 . 
     The system memory  924  may include any desired type of volatile and/or non-volatile memory such as, for example, static random access memory (SRAM), dynamic random access memory (DRAM), flash memory, read-only memory (ROM), etc. The mass storage memory  925  may include any desired type of mass storage device including hard disk drives, optical drives, tape storage devices, etc. 
     The I/O controller  922  performs functions that enable the processor  912  to communicate with peripheral input/output (I/O) devices  926  and  928  and a network interface  930  via an I/O bus  932 . The I/O devices  926  and  928  may be any desired type of I/O device such as, for example, a keyboard, a video display or monitor, a mouse, etc. The network interface  930  may be, for example, an Ethernet device, an asynchronous transfer mode (ATM) device, an 902.11 device, a DSL modem, a cable modem, a cellular modem, etc. that enables the processor system  910  to communicate with another processor system. 
     While the memory controller  920  and the I/O controller  922  are depicted in  FIG. 9  as separate blocks within the chipset  918 , the functions performed by these blocks may be integrated within a single semiconductor circuit or may be implemented using two or more separate integrated circuits. 
     Although certain systems, methods, apparatus, and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. To the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.