Patent Publication Number: US-2022239753-A1

Title: Methods and apparatus to facilitate meter to meter matching for media identification

Description:
RELATED APPLICATION(S) 
     This patent arises from a continuation of U.S. patent application Ser. No. 17/027,265 (now U.S. Pat. No. ______), which is titled “METHODS AND APPARATUS TO FACILITATE METER TO METER MATCHING FOR MEDIA IDENTIFICATION,” and which was filed on Sep. 21, 2020, which is a continuation of U.S. patent application Ser. No. 15/399,342 (now U.S. Pat. No. 10,785,329), which is titled “METHODS AND APPARATUS TO FACILITATE METER TO METER MATCHING FOR MEDIA IDENTIFICATION,” and which was filed on Jan. 5, 2017. U.S. patent application Ser. No. 17/027,265 and U.S. patent application Ser. No. 15/399,342 are hereby incorporated herein by reference in their respective entireties. Priority to U.S. patent application Ser. No. 17/027,265 and U.S. patent application Ser. No. 15/399,342 is hereby claimed. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to monitoring media presentation and/or consumption, and, more particularly, to methods and apparatus to facilitate meter to meter matching for media identification. 
     BACKGROUND 
     In recent years, presentation of media to users has been monitored and measured through the use of, for example, digital signatures for media identification. Media monitoring companies make reference signatures of identified media (e.g., television programs, music, audio broadcasts, internet videos, audio and/or visual advertisements, etc.), typically to develop a reference database. As unidentified media is presented to a user, a series of signatures of the unidentified media is made. The signatures of the unidentified media are then compared to the reference signatures. When the signatures of the unidentified media match one or more of the reference signatures, the unidentified media is identified. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an example environment in which a measurement system implemented with a matcher constructed in accordance with the teachings of this disclosure operates to monitor media presentation. 
         FIG. 2  is a block diagram of an example implementation of the matcher of the example measurement system of  FIG. 1 . 
         FIG. 3  illustrates an example signature string that may be processed by the example matcher of  FIGS. 1 and/or 2 . 
         FIG. 4  illustrates an example set of signature segments that are matched by the example matcher of  FIGS. 1 and/or 2 . 
         FIG. 5  illustrates example signature segments matched by the example matcher of  FIGS. 1 and/or 2 . 
         FIG. 6  illustrates an example uniform resource locator (URL) matched to one of the matching example signature segments of  FIG. 5  by the example matcher of  FIGS. 1 and/or 2 . 
         FIG. 7  is a flowchart representative of example machine-readable instructions that may be executed to implement the example matcher of  FIGS. 1 and/or 2 . 
         FIG. 8  is a flowchart representative of example machine-readable instructions that may be executed to implement block  715  of the example machine-readable instructions of  FIG. 7 . 
         FIG. 9  is a flowchart representative of example machine-readable instructions that may be executed to implement block  745  of the example machine-readable instructions of  FIG. 7 . 
         FIG. 10  is a flowchart representative of example machine-readable instructions that may be executed to implement block  755  of the example machine-readable instructions of  FIG. 7 . 
         FIG. 11  is a block diagram of an example processor platform capable of executing the instructions of  FIGS. 7, 8, 9 , and/or  10  to implement the example matcher of  FIGS. 1 and/or 2 . 
     
    
    
     The figures are not to scale. Instead, to clarify multiple layers and regions, the thickness of the layers may be enlarged in the drawings. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used in this patent, stating that any part (e.g., a layer, film, area, or plate) is in any way positioned on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, means that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. Stating that any part is in contact with another part means that there is no intermediate part between the two parts. 
     DETAILED DESCRIPTION 
     Audience measurement companies desire to gain knowledge regarding how users interact with client devices (e.g., televisions, handheld mobile devices, smartphones, laptop computers, tablets, etc.). For example, monitoring companies want to monitor media (e.g., television programs, music, Internet videos, etc.) that is presented on the client devices to, among other things, monitor exposure to advertisements, determine advertisement effectiveness, determine user behavior, identify purchasing behavior associated with various demographics, credit media consumption rates, etc. Some known systems have utilized meters coupled to client devices to generate digital signatures of the media that is presented on the client device. In some examples, the generated signatures are associated with respective timestamps of when the signatures were generated. The meter-generated signatures are then compared to a database of reference signatures to identify and thus monitor media being viewed and/or heard with the client device. 
     Signature or fingerprint-based media monitoring techniques generally use one or more inherent characteristics of the monitored media during a monitoring time interval to generate a substantially unique proxy for the media. Such a proxy is referred to as a signature or fingerprint, and can take any form (e.g., a series of digital values, a waveform, etc.) representative of any aspect(s) of the media signal(s)(e.g., the audio and/or video signals forming the media presentation being monitored). A signature may be a series of signatures collected in series over a timer interval. A good signature is repeatable when processing the same media presentation, but is unique relative to other (e.g., different) presentations of other (e.g., different) media. Accordingly, the term “fingerprint” and “signature” are used interchangeably herein and are defined herein to mean a proxy for identifying media that is generated from one or more inherent characteristics of the media. 
     Signature-based media monitoring generally involves determining (e.g., generating and/or collecting) signature(s) representative of a media signal (e.g., an audio signal and/or a video signal) output by a monitored media device and comparing the monitored signature(s) to one or more references signatures corresponding to known (e.g., reference) media sources. Various comparison criteria, such as a cross-correlation value, a Hamming distance, etc., can be evaluated to determine whether a monitored signature matches a particular reference signature. When a match between the monitored signature and one of the reference signatures is found, the monitored media can be identified as corresponding to the particular reference media represented by the reference signature that with matched the monitored signature. Because attributes, such as an identifier of the media, a presentation time, a broadcast channel, etc., are collected for the reference signature, these attributes may then be associated with the monitored media whose monitored signature matched the reference signature. Example systems for identifying media based on codes and/or signatures are long known and were first disclosed in Thomas, U.S. Pat. No. 5,481,294, which is hereby incorporated by reference in its entirety. 
     In some examples, a piece of media may not yet be represented by a reference signature in the reference database (e.g., a newly released song, a rare and/or old recording, a regional broadcast, user generated media, etc.). In some such examples, the media not yet represented by a reference signature in the reference database is referred to as unreferenced media. In some such examples, meter-generated signatures of the media presented on client devices will not match the reference signatures in the reference database (e.g., no corresponding reference signature will be present in the reference database to match the meter-generated signature). Further, in some examples, multiple meters respectively coupled to different client devices may generate signatures associated with the same unreferenced media that are separated in time with respect to the unreferenced media (e.g., a signature from the beginning of an unreferenced song made by a first meter and a signature from the end of the same unreferenced song made by a second meter). Thus, meter-generated signatures of unreferenced media may, in fact, correspond to the same piece of unreferenced media. 
     Example systems, methods, and apparatus disclosed herein collect, analyze, collate, and associate signatures representative of unknown (e.g., unreferenced) media. In some examples, segments of unknown signatures are analyzed (e.g., compared, sorted, etc.) to locate matching individual signatures. In some such examples, the segments of unknown signatures having matching individual signatures are counted. In some such examples, the segments of unknown signatures having matching individual signatures are associated with a uniform resource locator (URL). In some such examples, the segments of unknown signatures are associated with a piece of media via information provided by the URL. Thus, in some examples, the media associated with the segments of unknown signatures is identified and the segments of unknown signatures become known. In some examples, the collected signatures for unknown media and/or now-known signatures are added to the reference database. 
       FIG. 1  is a block diagram of an example environment  110  in which a measurement system  112  implemented with a matcher  114  constructed in accordance with the teachings of this disclosure operates to monitor media presentation. The example environment  110  includes the measurement system  112 , a client device  116 , a network meter  118 , a signature generating meter  120 , a central facility  122 , and a network  124 . In the illustrated example of  FIG. 1 , the client device  116  is shown as a television, although further client devices are possible (e.g., smartphones, radios, computers, laptops, music players, disc readers, streaming media receivers, etc.) In some examples, the environment  110  includes a plurality of client devices  116 , network meters  118 , and signature generating meters  120 . According to the illustrated example, the measurement system  112 , the client device  116 , the network meter  118 , the signature generating meter  120 , and the central facility  122  are interconnected via the example network  124 . The example client device  116  is transmissibly coupled to the network meter  118  (e.g., wired, over Wi-Fi, over Bluetooth®, etc.). The example client device  116  is transmissibly coupled to the signature generating meter  120  (e.g., wired, over Wi-Fi, over Bluetooth®, etc.). The example client device  116  receives network distributed media detectable by the network meter  118  via the network  124 . The example measurement system  112  is housed at the central facility  122 . Alternatively, the example measurement system  112  may be housed at a remote location. 
     The example signature generating meter  120  generates signatures of the media presented on the client device  116 . Based on the sampling rate of the example signature generating meter  120  and the length of time for which the media was presented, the signatures are generated as strings of individual signatures. For example, where the signature generating meter  120  has a sampling rate of three signatures per second and a piece of media is presented for one minute, a string of 180 individual signatures associated with the piece of media are produced in series. Further, the example signature generating meter  120  each generate the same signature strings for the same piece of presented media. For example, a first signature generating meter coupled to a first client device presenting a movie in Montana at 11:00 AM on a Saturday will generate the same (or substantially the same) signature string as a second signature generating meter coupled to a second client device presenting the same movie in Illinois at 8:00 PM on a Wednesday. Signature strings are to be explained in greater detail below in conjunction with  FIGS. 3-6 . The example signature generating meter  120  relays the signature strings to the example measurement system  112  via the example network  124 . 
     The example measurement system  112  includes the example matcher  114 , an example incoming signature database  126 , an example reference database  128 , an example unknown signature database  130 , an example URL database  132 , and an example creditor  134 . The example client device  116 , the example network meter  118 , the example signature generating meter  120 , the example central facility  122 , the example incoming signature database  126 , the example reference database  128 , the example URL database  132 , and the example creditor  134  are communicatively interconnected via the example network  124 . The example matcher  114  is communicatively coupled to the example incoming signature database  126 , the example reference database  128 , the example unknown signature database  130 , the example URL database  132 , and to the example creditor  134 . 
     In operation, when media is presented to users by the example client devices  116 , the example signature generating meters  120  generate signature strings of the media and relay the signature strings to the example incoming signature database  126  via the example network  124 . The example matcher  114  retrieves the signature strings from the incoming signature database  126  and attempts to match segments of the signature strings to a reference signature from the reference database  128 . Where a signature segment of a signature string matches a reference signature, the example matcher  114  extracts the matching signature segment from the signature string. The example matcher  114  sends the matching signature segment to the example creditor  134  for crediting. 
     However, where a signature segment does not match a reference signature (e.g., because the media underpinning the signature string is not yet represented with a reference signature in the reference database  128 ), the example matcher  114  deposits the unknown (e.g., unmatched) signature segment in the example unknown signature database  130 . As additional unknown signature segments are collected in the example unknown signature database  130 , the example matcher  114  retrieves unknown signature segments from the example unknown signature database  130  and attempts to stack (e.g., associate, connect, attach, etc.) matching unknown signature segments together and redeposits the stacked-together unknown signature segments in the example unknown signature database  130 . Thus, unknown signature segments originating from a single example signature generating meter  120  at different times and/or unknown signature segments originating from a plurality of example signature generating meters  120  are matched and associated together. Further features of the example matcher  114  related to stacking are described below with the aid of  FIGS. 2-6 . 
     The example network meter  118  deposits URLs of media presented on the example client device  116  in the URL database  132 . The URLs provide identifying information of the presented media. When the number of stacked-together unknown signature segments reaches a threshold count (e.g., 5, 10, 15, etc.), the example matcher  114  attempts to match the stacked-together unknown signature segments to the URLs from the example URL database  132 . Thus, the media represented by the unknown signature segments is identified, as will be described in greater detail with the aid of  FIGS. 2-6 . 
     The example matcher  114  sends the URL-matched stacked-together signature segments to the example creditor  134 . The example creditor  134  counts (e.g., credits) instances of matched signatures per piece of identified media within a specified time period (e.g., weekly, monthly, quarterly, etc.) and relays the count to the example central facility  122  via the example network  124 . The example matcher  114  sends the URL-matched signature segment to the example reference database  128  for storage as a reference signature, as will be described in greater detail with the aid of  FIGS. 2-6 . 
       FIG. 2  is a block diagram of an example implementation of the matcher  114  of the example measurement system  112  of  FIG. 1 . The example matcher  114  includes an example reference comparer  212 , an example duration filter  214 , an example unknown signature comparer  216 , an example stack counter  218 , and an example reference database updater  220 . 
     The example reference comparer  212  compares signature strings from the example incoming signature database  126  to reference signatures from the example reference database  128 . Where the example reference comparer  212  matches a segment of a signature string from the example incoming signature database  126  with a reference signature, the reference comparer  212  extracts the matched signature segment from the signature string. The example reference comparer  212  sends the matched signature segment to the example creditor  134 . Thus, unknown signature segments (e.g., segments of signature strings unmatched to a reference signature) are leftover. The example reference comparer  212  sends the unknown signature segments to the example duration filter  214 . 
     The example duration filter  214  analyzes the unknown signature segments based on a threshold length (e.g., a number of individual signatures, a time duration, etc.). The example duration filter  214  discards unknown signature segments that do not meet the threshold length. The example duration filter  214  sends unknown signature segments meeting the threshold length to the example unknown signature database  130 , as will be described in  FIGS. 3-5 . Thus, the example duration filter  214  acts as a high-pass filter for the unknown signature segments. 
     The example unknown signature comparer  216  retrieves and analyzes the individual signatures of the unknown signature segments from the example unknown signature database  130  to search for matching individual unknown signatures common to the unknown signature segments. When unknown signature segments having matching individual unknown signatures are found, the example unknown signature comparer  216  stacks (e.g., associates, connects, attaches, etc.) the unknown signature segments together at the matching individual unknown signatures and sends the unknown signature segments to the example stack counter  218 , as will be described in further detail below in conjunction with  FIGS. 3-5 . 
     The example stack counter  218  counts the number of matched stacked unknown signature segments from the example unknown signature comparer  216 . When the example stack counter  218  determines that the stacked-together unknown signature segments do not meet the threshold count described above, the stack counter  218  redeposits the stacked-together unknown signature segments in the example unknown signature database  130  When the example stack counter  218  determines that the stacked-together unknown signature segments meet the threshold count, the stack counter  218  sends the stacked-together unknown signature segments to the example reference database updater  220 . The example reference database updater  220  retrieves URLs from the example URL database  132 . The example reference database updater  220  compares timestamps of the individual signatures of the stacked-together unknown signature segments to timestamps of the retrieved URLs, as will be explained in greater detail in conjunction with  FIG. 6 . 
     Where the example reference database updater  220  finds matching timestamps (e.g., timestamps that indicate the same, or substantially the same, time of day and/or date) between a URL and an individual signature, the reference database updater  220  associates the unknown signature segment of the timestamp-matched individual signature with media-identifying information of the URL. The example reference database updater  220  further associates the remaining stacked-together unknown signature segments with the media identifying information. The example reference database updater  220  sends the media-identified stacked-together signature segments to the example creditor  134 . The example reference database updater  220  sends one of the media-identified signature segments to the example reference database  128  for storage as a reference signature (e.g., the reference database  128  holds singular examples of signature segments as reference signatures). 
     Where the example reference database updater  220  does not find matching timestamps between a URL and an individual signature, the reference database updater  220  returns the stacked-together unknown signature segments to the example stack counter  218 . In some such examples, the example stack counter  218  returns the stacked-together unknown signature segments to the example unknown signature database  130  as a stacked-together unknown signature segment bundle. The example stack counter  218  periodically (e.g., daily, weekly, monthly, quarterly, etc.) retrieves and sends the stacked-together unknown signature segment bundles from the example unknown signature database  130  to the example reference database updater  220  for a URL-matching reattempt. 
       FIG. 3  illustrates an example signature string that may be processed by the example matcher  114  of  FIGS. 1 and/or 2 . In the illustrated example of  FIG. 3 , signature string  312  is generated by the signature generating meter  120  of  FIG. 1 . In the illustrated example of  FIG. 3 , the signature string  312  is composed of a series of individual signatures  314 . The example individual signatures each include a value (e.g., a hexadecimal number, a binary number, an integer, an identifier, a letter, etc.) associated with a signature timestamp. For example, the individual signature  314  with value  316  “2F0” is associated with the signature timestamp  318  “07/15/2016-14:16:16” (e.g., the example signature generating meter  120  of  FIG. 1  generated value  316  “2F0” at 2:16:16 PM on Jul. 15, 2016). In the illustrated example of  FIG. 3 , reference signatures  320   a ,  320   b  are generated at the example central facility  122  of  FIG. 1  and stored in the example reference database  128  of  FIG. 1 . Reference signatures are composed of a series of the values (e.g., “2E1,” “2F1,” “2F2,” “2F3”). As the example reference signatures are used as a reference, they do not include signature timestamps. Alternatively, the reference signatures may be associated with a timestamp (e.g., reference signatures associated with live television, broadcast media, etc. may be associated with timestamps). 
     In operation, the example reference comparer  212  of  FIG. 2  searches for known signature segments by comparing the signature string  312  to the reference signatures. The example reference comparer  212  of  FIG. 2  searches for matching ordered values between the reference signature and the signature string. In the illustrated example of  FIG. 3 , reference signature  320   a  and the signature string  312  both include values “2E1,” “2F1,” “2F2,” and “2F3” in the same order “2E1, 2F1, 2F2, 2F3.” In the illustrated example of  FIG. 3 , reference signature  320   b  and the signature string  312  both include values “2EE,” “2EF,” and “2F0” in the same order “2EE, 2EF, 2F0.” In operation, the example reference comparer  212  of  FIG. 2  removes (e.g., cuts away, extracts, snips, excises, discards, etc.) the known signature segments from the signature string (e.g., removes known signature segments for the signature string to leave unknown signature segments). For example, the example reference comparer  212  of  FIG. 2  removes known signature segments  322   a ,  322   b  from the signature string  312 . The example reference comparer  212  of  FIG. 2  sends the removed known signature segments to the creditor  134  of  FIG. 1  to credit presentation, exposure, etc. of the known media. 
     After the known signature segments are removed from the signature string, an unknown signature segment remains (e.g., is leftover, persists, etc.). In the illustrated example of  FIG. 3 , after known signature segments  322   a ,  322   b  are removed from the signature string  312 , the unknown signature segment  324  remains. The example reference comparer  212  of  FIG. 2  sends the unknown signature segment  324  to the example duration filter  214  of  FIG. 2 . 
     The example duration filter  214  of  FIG. 2  filters unknown signature segments based on a threshold length (e.g., 7 individual signatures, 30 seconds, etc.). In operation, the example duration filter  214  of  FIG. 2  discards unknown signature segments shorter than the threshold length and sends unknown signature segments meeting the threshold length to the example unknown signature database  130  of  FIG. 1 . In the illustrated example of  FIG. 3 , given an example threshold length of 7 individual signatures, the example unknown signature segment  324  exceeds the threshold length and would thus be sent by the example duration filter  214  of  FIG. 2  to the unknown signature database  130  of  FIG. 1 . 
       FIG. 4  illustrates an example set of signature segments that are matched by the example matcher  114  of  FIGS. 1 and/or 2 . In operation, the example unknown signature comparer  216  of  FIG. 2  retrieves a candidate unknown signature segment (e.g., the example unknown signature segment  324  of  FIG. 3 ) and a comparison unknown signature segment from the example unknown signature database  130  of  FIG. 1 . The comparison unknown signature segment is composed of a series of individual signatures, each having a value and an associated signature timestamp. In the illustrated example of  FIG. 4 , the example unknown signature retriever  216  of  FIG. 2  has retrieved unknown signature segment  324  of  FIG. 3  as candidate unknown signature segment  412  and comparison unknown signature segment  414  from the example unknown signature database  130  of  FIG. 1 . 
     The example unknown signature comparer  216  aligns a match portion  416  of the candidate unknown signature segment  412  meeting a match threshold (e.g., 7 individual signatures, etc.) with the earliest individual signatures of the comparison unknown signature segment  414  meeting the match threshold. In some examples, the threshold length and the match threshold are equal in length. In operation, the example unknown signature comparer  216  of  FIG. 2  then determines whether the values of the aligned individual signatures match. In operation, when the values of the aligned individual signatures do not match, as denoted by crossed lines  418  in  FIG. 4 , the example unknown signature comparer  216  of  FIG. 2  advances the candidate unknown signature segment  412  along the comparison unknown signature segment  414  by one individual signature, as denoted by advancement arrow  420 , and repeats the aligned individual signature value matching determination. In operation, the unknown signature comparer  216  of  FIG. 2  repeats this advancing and determining process, as denoted by transition arrow  422  in  FIG. 4 , until matching values between aligned individual signatures meeting the match threshold are found, as denoted by double-arrowed lines  424 . In operation, the example unknown signature comparer  216  of  FIG. 2  then stacks the candidate and comparison unknown signature segments  412 ,  414  together at the matching values, as will be explained greater detail in conjunction with  FIG. 5 . 
     In operation, when matching values between the candidate unknown signature segment and the comparison unknown signature segment meeting the match threshold are not found, the example unknown signature comparer  216  of  FIG. 2  returns the comparison unknown signature segment to the example unknown signature database  130  of  FIG. 1  and selects a further comparison unknown signature segment to continue the comparison process. In operation, when the example unknown signature database  130  of  FIG. 1  has been exhausted of comparison unknown signature segments, the example unknown signature comparer  216  of  FIG. 2  returns the candidate unknown signature segment to the example unknown signature database  130  of  FIG. 1  and selects a further candidate unknown signature segment to continue the comparison process. 
       FIG. 5  illustrates example signature segments matched by the example matcher  114  of  FIGS. 1 and/or 2 . In operation, as the example unknown signature comparer  216  of  FIG. 2  matches and stacks unknown signature segments, the example stack counter  218  of  FIG. 2  counts the number of matched stacked unknown signature segments. In the illustrated example of  FIG. 5 , because five unknown signature segments  512   a ,  512   b ,  512   c ,  512   d ,  512   e  include values “2CB,” “45D,” “26F,” “4CA,” “4C5,” “910,” and “1BF” in the order “2CB, 45D, 26F, 4CA, 4C5, 910, 1BF,” the example stack counter  218  of  FIG. 2  counts five matched stacked unknown signature segments. In operation, when the number of matched stacked unknown signature segments meets a count threshold (e.g., five matched stacked unknown signature segments), the example stack counter  218  of  FIG. 2  extracts a match core. The match core includes the individual signatures across which the unknown signature segments are stacked (e.g., the match core is composed of the portions of the unknown signature segments that have matching ordered values). In the illustrated example of  FIG. 5 , the match core  514  includes the individual signatures of unknown signature segments  512   a ,  512   b ,  512   c ,  512   d ,  512   e  that have ordered values “2CB, 45D, 26F, 4CA, 4C5, 910, 1BF,” as denoted by the double-arrowed lines  424  of  FIG. 4 . The example stack counter  218  of  FIG. 2  sends the match core to the example reference database updater  220  of  FIG. 2 . 
       FIG. 6  illustrates an example uniform resource locator (URL) matched to an unknown signature segment by the example matcher  114  of  FIGS. 1 and/or 2 . The URL is generated by the example network meter  118  of  FIG. 1  based on online activity by a user and stored in the example URL database  132 . The URL is associated with a network timestamp, a media title, and a media provider. In the illustrated example of  FIG. 6 , the URL  612  “www.wechute.com/video=895783939” is associated with the network timestamp  614  “07/08/2016-18:43:23,” the media title  616  “Super Silly Catz!,” and the media provider  618  “Kittyfan5000.” In operation, the example reference database updater  220  of  FIG. 2  retrieves the associated URL, network timestamp, media title, and media provider from the example URL database  132  of  FIG. 1 . In operation, to correlate the match core to the URL, the example reference database updater  220  then compares the network timestamp with the signature timestamps of the match core. In operation, when the example reference database updater  220  of  FIG. 2  matches the network timestamp with one of the signature timestamps, the reference database updater  220  associates the unknown signature segment of the network timestamp-matching signature timestamp with the URL, the media title and the media provider, as denoted in  FIG. 6  by association arrow  620 . In operation, the example reference database updater  220  of  FIG. 2  associates the remaining unknown signature segments of the match core with the URL, the media title, and the media provider via the unknown signature segment that has the network timestamp-matching signature timestamp as denoted by double-arrowed lines  424 . In the illustrated example of  FIG. 6 , the unknown signature segment  512   c  of  FIG. 5  including signature timestamp  622  “07/08/2016-18:43:23” is associated with URL  612  “www.wechute.com/video=895783939,” media title  616  “Super Silly Catz!,” and media provider  618  “Kittyfan5000” via the network timestamp  614  “07/08/2016-18:43:23.” In the illustrated example of  FIG. 6 , the example reference database updater  220  of  FIG. 2  associates the remaining unknown signature segments  512   a ,  512   b ,  512   d ,  512   e  of the match core  514  with the URL  612  “www.wechute.com/video=895783939,” the media title  616  “Super Silly Catz!,” and the media provider  618  “Kittyfan5000” via the unknown signature segment  512   c  that has signature timestamp  622  “07/08/2016-18:43:23.” Thus, unknown signature segments of the match core are identified as representative of the media of the media title. 
     In operation, the example reference database updater  220  of  FIG. 2  sends the match core to the example creditor  134  of  FIG. 1  which credits presentation views to the media of media title according to the number of now-known signature segments in the match core. In operation, the example reference database updater  220  of  FIG. 2  updates the example reference database  128  of  FIG. 1  with the ordered values of the now-known signature segments and the associated media title and media provider. In the illustrated example of  FIG. 6 , the ordered values “2CB, 45D, 26F, 4CA, 4C5, 910, 1BF” shared by the unknown signature segments  512   a ,  512   b ,  512   c ,  512   d ,  512   e  and the associated media title  616  and media provider  618  are added to the reference database  128  by the reference updater  220 . Thus, in some examples, unknown signature segments are transformed into reference signatures. 
     While an example manner of implementing the example matcher  114  of  FIG. 1  is illustrated in  FIG. 2 , one or more of the elements, processes and/or devices illustrated in  FIG. 2  may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further, the example reference comparer  212 , the example duration filter  214 , the example unknown signature comparer  216 , the example stack counter  218 , the example reference database updater  220  and/or, more generally, the example matcher  114  of  FIGS. 1-2  may be implemented by hardware, software, firmware and/or any combination of hardware, software and/or firmware. Thus, for example, any of the example reference comparer  212 , the example duration filter  214 , the example unknown signature comparer  216 , the example stack counter  218 , the example reference database updater  220  and/or, more generally, the example matcher  114  could be implemented by one or more analog or digital circuit(s), logic circuits, 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)). When reading any of the apparatus or system claims of this patent to cover a purely software and/or firmware implementation, at least one of the example matcher  114 , the example reference comparer  212 , the example duration filter  214 , the example unknown signature comparer  216 , the example stack counter  218  and/or the example reference database updater  220  is/are hereby expressly defined to include a tangible computer readable storage device or storage disk such as a memory, a digital versatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc. storing the software and/or firmware. Further still, the example matcher  114  of  FIGS. 1 and/or 2  may include one or more elements, processes and/or devices in addition to, or instead of, those illustrated in  FIG. 2 , and/or may include more than one of any or all of the illustrated elements, processes and devices. 
     Flowcharts representative of example machine readable instructions for implementing the example matcher  114  of  FIGS. 1 and/or 2  are shown in  FIGS. 7-10 . In this example, the machine readable instructions comprise a program(s) for execution by a processor such as the processor  1112  shown in the example processor platform  1100  discussed below in connection with  FIG. 11 . The program may be embodied in software stored on a tangible computer readable storage medium such as a CD-ROM, a floppy disk, a hard drive, a digital versatile disk (DVD), a Blu-ray disk, or a memory associated with the processor  1112 , but the entire program(s) and/or parts thereof could alternatively be executed by a device other than the processor  1112  and/or embodied in firmware or dedicated hardware. Further, although the example program(s) is described with reference to the flowcharts illustrated in  FIGS. 7-10 , many other methods of implementing the example matcher  114  may alternatively be used. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, eliminated, or combined. 
     As mentioned above, the example processes of  FIGS. 7-10  may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a tangible computer readable storage medium such as a hard disk drive, a flash memory, a read-only memory (ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, a random-access memory (RAM) and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term tangible computer readable storage medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, “tangible computer readable storage medium” and “tangible machine readable storage medium” are used interchangeably. Additionally or alternatively, the example processes of  FIGS. 7-10  may be implemented using coded instructions (e.g., computer and/or machine readable instructions) stored on a non-transitory computer and/or machine readable medium such as a hard disk drive, a flash memory, a read-only memory, a compact disk, a digital versatile disk, a cache, a random-access memory and/or any other storage device or storage disk in which information is stored for any duration (e.g., for extended time periods, permanently, for brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term non-transitory computer readable medium is expressly defined to include any type of computer readable storage device and/or storage disk and to exclude propagating signals and to exclude transmission media. As used herein, when the phrase “at least” is used as the transition term in a preamble of a claim, it is open-ended in the same manner as the term “comprising” is open ended. 
       FIG. 7  is a flowchart representative of example machine-readable instructions  710  that may be executed to implement the example matcher  114  of  FIGS. 1 and/or 2 . The example instructions  710  may be performed, for example, to match unknown signature segments together to identify unknown presented media. 
     To start, the example matcher  114  determines eligible unknown signature segments (e.g., signatures that are not identified in a reference database and meet a threshold length) for analysis, as will be described in greater detail in connection with  FIG. 8  (block  715 ). Next, the example unknown signature comparer  216  of the example matcher  114  selects a candidate unknown signature segment from the unknown signature database  130  of the example measurement system  112  (block  720 ). The example unknown signature comparer  216  further selects a match portion of the candidate unknown signature segment (block  725 ). The example unknown signature comparer  216  further selects a comparison unknown signature segment from the unknown signature database  130  (block  730 ). The example unknown signature comparer  216  then aligns the match portion with the comparison unknown signature segment (block  735 ). The example unknown signature comparer  216  then compares the match portion and the comparison unknown signature segment to determine whether the individual signatures of the match portion match the individual signatures of the comparison unknown signature segment aligned with the match portion (block  740 ). 
     If the individual signatures of the match portion match the individual signatures of the comparison unknown signature segment aligned with the match portion, the example unknown signature comparer  216  stacks the matching signature segments at the matching individual signatures, as will be described in greater detail in connection with  FIG. 9  (block  745 ). Next, the example stack counter  218  of the example matcher  114  determines whether the number of matching unknown signature segments meets the count threshold (block  750 ). If the number of matching unknown signature segments does not meet the count threshold, the instructions  710  return to block  730 . 
     If the number of matching unknown signature segments meets the count threshold, the example reference database updater  220  of the example matcher  114  builds a reference signature from the matching unknown signature segments, as will be described in greater detail in connection with  FIG. 10 , (block  755 ) and the instructions  710  end. 
     Referring back to block  740 , if the individual signatures of the match portion do not match the individual signatures of the comparison unknown signature segment aligned with the match portion, the example unknown signature comparer  216  determines whether the match portion is at the latest-in-time end of the comparison unknown signature segment (block  760 ). If the match portion is not at the latest-in-time end of the comparison unknown signature segment, the example unknown signature comparer  216  advances the candidate unknown signature segment along the comparison unknown signature segment (block  765 ) and the instructions  710  return to block  740 . If the match portion is at the latest-in-time end of the comparison unknown signature segment, the example unknown signature comparer  216  determines whether additional unanalyzed unknown signature segments are available for comparison (block  770 ). 
     If additional unanalyzed unknown signature segments are available for comparison, the instructions  710  return to block  730 . If additional unanalyzed unknown signature segments are not available for comparison, the example unknown signature comparer  216  determines whether the match portion is at the earliest-in-time end of the candidate unknown signature segment (block  775 ). 
     If the match portion is not at the earliest-in-time end of the candidate unknown signature segment, the instructions  710  return to block  725 . If the match portion is at the earliest-in-time end of the candidate unknown signature segment, the example unknown signature comparer  216  determines whether further unanalyzed unknown signature segments are available for examination as candidate unknown signature segments (block  780 ). 
     If further unanalyzed unknown signature segments are available for examination as candidate unknown signature segments, the instructions  710  return to block  720 . If further unanalyzed unknown signature segments are not available for examination as candidate unknown signature segments, the instructions  710  return to block  715   
       FIG. 8  is a flowchart representative of example machine-readable instructions that may be executed to implement block  715  of the example machine-readable instructions of  FIG. 7 . 
     To determine eligible unknown signature segments, the example reference comparer  212  of  FIG. 2  of the example matcher  114  of  FIGS. 1 and 2  retrieves incoming signature strings from the example incoming signature database  126  of the example measurement system  112  of  FIG. 1  collected from the example signature generating meters  120  of  FIG. 1  (block  815 ). Next, the example reference comparer  212  removes signature segments from the signature strings that match reference signatures stored in the example reference database  128  of the example measurement system  112  from unknown signature segments (block  820 ). Then, the example creditor  134  of  FIG. 2  of the example measurement system  112  of  FIG. 1  credits media according to the reference matched signature segments (block  825 ). Further, the example duration filter  214  of  FIG. 2  of the example matcher  114  discards unknown signature segments that do not meet a threshold length and stores unknown signature segments meeting the length threshold in the example unknown signature database  130  (block  830 ). The instructions  715  of  FIG. 8  end and control returns to block  720  of  FIG. 7 . 
       FIG. 9  is a flowchart representative of example machine-readable instructions that may be executed to implement block  745  of the example machine-readable instructions of  FIG. 7 . 
     To stack matching unknown signature segments, the example unknown signature comparer  216  determines whether additional individual signatures of the candidate unknown signature segment and the comparison unknown signature segment match (block  915 ). 
     If additional individual signatures of the candidate unknown signature segment and the comparison unknown signature segment match, the example unknown signature comparer  216  logs the additional matches (block  920 ). Next, the example unknown signature comparer  216  associates the candidate unknown signature segment and the comparison unknown segment at the matching individual signatures (block  925 ). The instructions  745  of  FIG. 9  end and control returns to block  750  of  FIG. 7 . 
     If additional individual signatures of the candidate unknown signature segment and the comparison unknown signature segment do not match, the instructions  710  progress to block  925 . 
       FIG. 10  is a flowchart representative of example machine-readable instructions that may be executed to implement block  755  of the example machine-readable instructions of  FIG. 7 . 
     To build a reference signature from the stacked unknown signature segments, the example reference database updater  220  correlates the stacked unknown signature segments to a URL from the URL database  132  via a signature timestamp of the stacked unknown signature segments and a network timestamp associated with the URL (block  1015 ). Then, the example reference database updater  220  identifies the media represented by the unknown signature segment is from the URL (block  1020 ). Further, the example reference database updater  220  updates the example reference database  128  with the now-known signature segment as a reference signature (block  1025 ). The instructions  755  of  FIG. 10  then end. 
       FIG. 11  is a block diagram of an example processor platform  1100  capable of executing the instructions of  FIGS. 7-10  to implement the matcher  114  of  FIG. 1  and/or  FIG. 2 . The processor platform  1100  can be, for example, a server, a personal computer, a mobile device (e.g., a cell phone, a smart phone, a tablet such as an iPad®), a personal digital assistant (PDA), an Internet appliance, a DVD player, a CD player, a digital video recorder, a Blu-ray player, a gaming console, a personal video recorder, a set top box, or any other type of computing device. 
     The processor platform  1100  of the illustrated example includes a processor  1112 . The processor  1112  of the illustrated example is hardware. For example, the processor  1112  can be implemented by one or more integrated circuits, logic circuits, microprocessors or controllers from any desired family or manufacturer. 
     The processor  1112  of the illustrated example includes a local memory  1113  (e.g., a cache) and the matcher  114  including the reference comparer  212 , the duration filter  214 , the unknown signature comparer  216 , the stack counter  218 , and the reference database updater  220 . The processor  1112  of the illustrated example is in communication with a main memory including a volatile memory  1114  and a non-volatile memory  1116  via a bus  1118 . The volatile memory  1114  may be implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or any other type of random access memory device. The non-volatile memory  1116  may be implemented by flash memory and/or any other desired type of memory device. Access to the main memory  1114 ,  1116  is controlled by a memory controller. 
     The processor platform  1100  of the illustrated example also includes an interface circuit  1120 . The interface circuit  1120  may be implemented by any type of interface standard, such as an Ethernet interface, a universal serial bus (USB), and/or a PCI express interface. 
     In the illustrated example, one or more input devices  1122  are connected to the interface circuit  1120 . The input device(s)  1122  permit(s) a user to enter data and commands into the processor  1112 . The input device(s)  1122  can be implemented by, for example, an audio sensor, a microphone, a camera (still or video), a keyboard, a button, a mouse, a touchscreen, a track-pad, a trackball, isopoint and/or a voice recognition system. 
     One or more output devices  1124  are also connected to the interface circuit  1120  of the illustrated example. The output devices  1124  can be implemented, for example, by display devices (e.g., a light emitting diode (LED), an organic light emitting diode (OLED), a liquid crystal display, a cathode ray tube display (CRT), a touchscreen, a tactile output device, a light emitting diode (LED), a printer and/or speakers). The interface circuit  1120  of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip or a graphics driver processor. 
     The interface circuit  1120  of the illustrated example also includes a communication device such as a transmitter, a receiver, a transceiver, a modem and/or network interface card to facilitate exchange of data with external machines (e.g., computing devices of any kind) via a network  1126  (e.g., an Ethernet connection, a digital subscriber line (DSL), a telephone line, coaxial cable, a cellular telephone system, etc.). 
     The processor platform  1100  of the illustrated example also includes one or more mass storage devices  1128  for storing software and/or data. Examples of such mass storage devices  1128  include floppy disk drives, hard drive disks, compact disk drives, Blu-ray disk drives, RAID systems, and digital versatile disk (DVD) drives. 
     The coded instructions  1132  of  FIGS. 7-10  may be stored in the mass storage device  1128 , in the volatile memory  1114 , in the non-volatile memory  1116 , and/or on a removable tangible computer readable storage medium such as a CD or DVD. 
     From the foregoing, it will be appreciated that the above disclosed methods, apparatus and articles of manufacture may aid in identifying, analyzing, comparing, and understanding media and when that media is presented. By associating signatures representative of a piece of unknown (e.g., unreferenced) media from multiple signature generating meters together to form a match core, the unknown media may be more quickly identified, which in turn may provide insights into the preferences and habits of media consumers. Further, comparing signature timestamps of a match core to a network timestamp associated with a URL may be accomplished in fewer operations by a processor, thus reducing processor demand in a computer, as compared to comparing the signature timestamps of each individual unknown signature to the network timestamp piecemeal. Moreover, identifying an unknown signature segment via a URL may make reference signature generation more efficient. Learning about audio media consumers&#39; preferences and habits may help media broadcasters to provide media (e.g., music, movies, television programs, etc.) that media consumers want to hear and to additionally deliver targeted advertisements for products that may interest media consumers. 
     Although certain example methods, apparatus and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent.