Patent Publication Number: US-2023162745-A1

Title: Systems and methods to improve timestamp transition resolution

Description:
RELATED APPLICATIONS 
     This patent arises from a continuation of U.S. patent application Ser. No. 17/365,842, titled “SYSTEMS AND METHODS TO IMPROVE TIMESTAMP TRANSITION RESOLUTION,” filed Jul. 1, 2021, which is a continuation of U.S. patent application Ser. No. 16/943,715, titled “SYSTEMS AND METHODS TO IMPROVE TIMESTAMP TRANSITION RESOLUTION,” filed Jul. 30, 2020, which is a continuation of U.S. patent application Ser. No. 16/450,057, titled “SYSTEMS AND METHODS TO IMPROVE TIMESTAMP TRANSITION RESOLUTION,” filed Jun. 24, 2019, which is a continuation of U.S. patent application Ser. No. 15/800,466, titled “SYSTEMS AND METHODS TO IMPROVE TIMESTAMP TRANSITION RESOLUTION,” filed Nov. 1, 2017, which claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/573,798, which was filed on Oct. 18, 2017. Priority to U.S. patent application Ser. No. 17/365,842, U.S. patent application Ser. No. 16/943,715, U.S. patent application Ser. No. 16/450,057, U.S. patent application Ser. No. 15/800,466, and U.S. Provisional Patent Application No. 62/573,798 is claimed. U.S. patent application Ser. No. 17/365,842, U.S. patent application Ser. No. 16/943,715, U.S. patent application Ser. No. 16/450,057, U.S. patent application Ser. No. 15/800,466, and U.S. Provisional Patent Application No. 62/573,798 are hereby incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to media watermarking, and, more particularly, to systems and methods to improve timestamp transition resolution. 
     BACKGROUND 
     Watermarks can be embedded or otherwise included in media to enable additional information to be conveyed with the media. For example, audio watermarks can be embedded or otherwise included in the audio data/signal portion of a media stream, file and/or signal to convey data, such as media identification information, copyright protection information, timestamps indicative of broadcast time, etc., with the media. Such watermarks enable monitoring of the distribution and/or use of media, such as by detecting watermarks present in television broadcasts, radio broadcasts, streamed multimedia, etc., to identify the particular media being presented to viewers, listeners, users, etc. Such information can be valuable to advertisers, content providers, and the like. 
     Prior media monitoring systems employing watermarks typically include watermark decoders that identify the information contained in the watermarks. Some prior systems identify the timestamps in the watermarks and transitions between timestamps to a relatively coarse resolution, such as a resolution of one minute. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram of an example media monitoring system, which includes an example timestamp transition resolution enhancer constructed in accordance with the teachings of this disclosure. 
         FIG.  2    illustrates an example watermark to be detected by the example media device monitor of  FIG.  1   . 
         FIG.  3    a block diagram illustrating an example implementation of the timestamp transition resolution enhancer of  FIG.  1   . 
         FIG.  4    illustrates an example mapping of detected watermarks, timestamps, and timestamp transition resolution enhancement performed in accordance with the teachings of this disclosure. 
         FIG.  5    is a flowchart representative of first example machine readable instructions that may be executed to implement the example media monitoring system of  FIG.  1    and/or the example timestamp transition resolution enhancer of  FIG.  3   . 
         FIG.  6    is a block diagram of an example processor platform structured to execute the example machine readable instructions of  FIG.  5    to implement the example media monitoring system of  FIG.  1    and/or the example timestamp transition resolution enhancer of  FIG.  3   . 
     
    
    
     The figures are not to scale. 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. 
     DETAILED DESCRIPTION 
     Systems, methods, apparatus, and articles of manufacture (e.g., non-transitory, physical storage media) to improve timestamp transition resolution in watermarks are disclosed herein. Example watermark timestamp transition resolution enhancing systems include a watermark detector to detect watermarks and a decoder to decode timestamps in respective ones of the watermarks. Some such example systems also include a timestamp transition resolution enhancer to estimate a first transition window indicative of a transition between a first time period to a second time period based on a first one of the timestamps and a second one of the timestamps. In some examples, the timestamp transition resolution enhancer also estimates, when the first transition window does not satisfy a threshold, a second transition window indicative of a transition between the second time period and a third time period based on the second timestamp and a third one of the timestamps. In addition, the example timestamp transition resolution enhancer of some examples determines a first mapped transition window based on an intersection of the first transition window and the second transition window and sets the first mapped transition window as a reference time transition window for subsequent time periods. 
     In some examples, the timestamp transition resolution enhancer is to set the first transition window as an established time transition when the first transition window satisfies the threshold. 
     In some examples, the timestamp transition resolution enhancer is to set the first mapped transition window as an established time transition when the first mapped transition window satisfies the threshold. 
     In some examples, the timestamp transition resolution enhancer is to estimate, when the first mapped transition window does not satisfy the threshold, a third transition window indicative of a transition between the third time period and a fourth time period of time based on the third timestamp and a fourth one of the timestamps. In such examples, the timestamp transition resolution enhancer also is to determine a second mapped transition window based on an intersection of the first mapped transition window and the third transition window and set the second mapped transition window as the reference time transition window. 
     In some examples, the timestamp transition resolution enhancer is to set the second mapped transition window as an established time transition when the second mapped transition window satisfies the threshold. 
     In some examples, the timestamp transition resolution enhancer is to set an established time transition based on at least one of the first transition window or the first mapped transition window satisfying the threshold. In such examples, the timestamp transition resolution enhancer also is to retroactively map time transitions in the media signal based on the established time transition. 
     In some examples, respective ones of the time periods have minute durations and the threshold is about five seconds. 
     In some examples, the first transition window is identified when a first timestamp in a first watermark is different than a second timestamp in a second watermark. 
     Also disclosed herein are example methods that include estimating, by executing an instruction with a processor, a first transition window indicative of a transition between a first time period to a second time period based on a first timestamp of a first watermark and a second timestamp of a second watermark. Some such example methods also include estimating, by executing an instruction with a processor when the first transition window does not satisfy a threshold, a second transition window indicative of a transition between the second time period and a third time period based on the second timestamp and a third timestamp. In addition, some example methods include determining, by executing an instruction with a processor, a first mapped transition window based on an intersection of the first transition window and the second transition window and setting the first mapped transition window as the reference time transition window for subsequent time periods. 
     Some example methods also include setting, by executing an instruction with a processor, the first transition window as an established time transition when the first transition window satisfies the threshold. 
     Some example methods also include setting, by executing an instruction with a processor, the first mapped transition window as an established time transition when the first mapped transition window satisfies the threshold. 
     Some example methods also include estimating, by executing an instruction with a processor when the first mapped transition window does not satisfy the threshold, a third transition window indicative of a transition between the third time period and a fourth time period of time based on the third timestamp and a fourth timestamp. Such example methods also include determining, by executing an instruction with a processor, a second mapped transition window based on an intersection of the first mapped transition window and the third transition window and setting the second mapped transition window as the reference time transition window. 
     Some example methods include setting, by executing an instruction with a processor, the second mapped transition window as an established time transition when the second mapped transition window satisfies the threshold. 
     Some example methods include setting, by executing an instruction with a processor, an established time transition based on at least one of the first transition window or the first mapped transition window satisfying the threshold. Such example methods also include retroactively mapping, by executing an instruction with a processor, time transitions in the media signal based on the established time transition. 
     Some example methods also include respective ones of the time periods have minute durations and the threshold is about five seconds. 
     Some example methods also include comparing, by executing an instruction with a processor, a first timestamp in a first watermark and a second time stamp in a second watermark and identifying, by executing an instruction with a processor, the first transition window when the first timestamp and the second timestamp are different. 
     Also disclosed herein are non-transitory machine-readable storage media comprising machine-readable instructions which, when executed, cause a machine to at least: estimate a first transition window indicative of a transition between a first time period to a second time period based on a first timestamp of a first watermark and a second timestamp of a second watermark. The example instructions of some such examples also cause the machine to estimate, when the first transition window does not satisfy a threshold, a second transition window indicative of a transition between the second time period and a third time period based on the second timestamp and a third timestamp. In addition, the example instructions of some such examples cause the machine to determine a first mapped transition window based on an intersection of the first transition window and the second transition window and set the first mapped transition window as the reference time transition window for subsequent time periods. 
     In some examples, the instructions cause the machine to set the first transition window as an established time transition when the first transition window satisfies the threshold. 
     In some examples, the instructions further cause the machine to set the first mapped transition window as an established time transition when the first mapped transition window satisfies the threshold. 
     In some examples, the instructions further cause the machine to estimate, when the first mapped transition window does not satisfy the threshold, a third transition window indicative of a transition between the third time period and a fourth time period of time based on the third timestamp and a fourth timestamp. In such examples, the instructions also cause the machine to determine a second mapped transition window based on an intersection of the first mapped transition window and the third transition window and set the second mapped transition window as the reference time transition window. 
     In some examples, the instructions further cause the machine to set the second mapped transition window as an established time transition when the second mapped transition window satisfies the threshold. 
     In some examples, the instructions further cause the machine to set an established time transition based on at least one of the first transition window or the first mapped transition window satisfying the threshold and retroactively map time transitions in the media signal based on the established time transition. 
     In some examples, respective ones of the time periods have minute durations and the threshold is about five seconds. 
     In some examples, the instructions further cause the machine to identify the first transition window when a first timestamp in a first watermark is different than a second timestamp in a second watermark. 
     Also disclosed herein are example systems that include means for detecting watermarks and means for decoding timestamps in respective ones of the watermarks. Such example systems also includes means for estimating transition windows by estimating a first transition window indicative of a transition between a first time period to a second time period based on a first one of the timestamps and a second one of the timestamps, and estimating, when the first transition window does not satisfy a threshold, a second transition window indicative of a transition between the second time period and a third time period based on the second timestamp and a third one of the timestamps. Such example systems also include means for determining a first mapped transition window based on an intersection of the first transition window and the second transition window. In addition, such example systems include means for setting the first mapped transition window as a reference time transition window for subsequent time periods. 
     In some example systems, the means for setting is to set the first transition window as an established time transition when the first transition window satisfies the threshold. 
     In some example systems, the means for setting is to set the first mapped transition window as an established time transition when the first mapped transition window satisfies the threshold. 
     In some example systems, when the first mapped transition window does not satisfy the threshold, the means for estimating is to estimate a third transition window indicative of a transition between the third time period and a fourth time period of time based on the third timestamp and a fourth one of the timestamps. In such example systems, the means for determining is to determine a second mapped transition window based on an intersection of the first mapped transition window and the third transition window. In addition, in such examples, the means for setting is to set the second mapped transition window as the reference time transition window. 
     In some examples systems, the means for setting is to set the second mapped transition window as an established time transition when the second mapped transition window satisfies the threshold. 
     In some examples systems, the means for setting is to set an established time transition based on at least one of the first transition window or the first mapped transition window satisfying the threshold. In such example systems, the means for setting also is to retroactively map time transitions in the media signal based on the established time transition. 
     In some examples systems, respective ones of the time periods have minute durations and the threshold is about five seconds. 
     In some examples systems, the means for estimating is to identify the first transition window when a first timestamp in a first watermark is different than a second timestamp in a second watermark. 
     Also disclosed herein are systems that include a watermark detector to detect watermarks and a decoder to decode timestamps in respective ones of the watermarks. Some such example systems include a timestamp transition resolution enhancer to determine moments of transition between time periods of media containing the watermarks based on the timestamps by: (a) estimating a coarse transition window between two time periods; (b) mapping a prior transition window estimate to the estimate of (a); (c) narrowing to a fine transition window estimate based on an overlap between the estimate of (a) and (b); (d) comparing the estimate of (c) to a threshold; (e) repeating (a) through (d) for successive time periods using the fine transition window estimate of (c) as the prior transition window estimate of (b) until the fine transition window estimate of (c) satisfies the threshold; and (e) establishing the fine transition window estimate as an established moment of transition between time periods when the estimate of (c) satisfies the threshold. 
     In some examples, the timestamp transition resolution enhancer is to identify the moments of transition between time periods of the media signal based on the established moment of transition. 
     In some examples, the time periods correspond to successive minutes of the media signal and the threshold is about five seconds. 
     Also disclosed herein are methods that include detecting, by executing an instruction with a processor, watermarks and decoding, by executing an instruction with a processor, timestamps in respective ones of the watermarks. Some such example methods also include determining, by executing an instruction with a processor, moments of transition between time periods of media containing the watermarks based on the timestamps by: (a) estimating a coarse transition window between two time periods; (b) mapping a prior transition window estimate to the estimate of (a); (c) narrowing to a fine transition window estimate based on an overlap between the estimate of (a) and (b); (d) comparing the estimate of (c) to a threshold; (e) repeating (a) through (d) for successive time periods using the fine transition window estimate of (c) as the prior transition window estimate of (b) until the fine transition window estimate of (c) satisfies the threshold; and (f) establishing the fine transition window estimate as an established moment of transition between windows when the estimate of (c) satisfies the threshold. 
     In some examples, the method includes identifying, by executing an instruction with a processor, the moments of transition between time periods of the media signal based on the established moment of transition. 
     In some examples, the method includes the time periods corresponding to successive minutes of the media signal and the threshold is about five seconds. 
     Also disclosed herein are non-transitory storage media including machine-readable instructions which, when executed, cause a machine to at least detect watermarks and decode timestamps in respective ones of the watermarks. In some examples, the instructions also cause the machine to determine moments of transition between time periods of media containing the watermarks based on the timestamps by: (a) estimating a coarse transition window between two time periods; (b) mapping a prior transition window estimate to the estimate of (a); (c) narrowing to a fine transition window estimate based on an overlap between the estimate of (a) and (b); (d) comparing the estimate of (c) to a threshold; (e) repeating (a) through (d) for successive time periods using the fine transition window estimate of (c) as the prior transition window estimate of (b) until the fine transition window estimate of (c) satisfies the threshold; and (f) establishing the fine transition window estimate as an established moment of transition between windows when the estimate of (c) satisfies the threshold. 
     In some examples, the instructions further cause the machine to identify the moments of transition between time periods of the media signal based on the established moment of transition. 
     In some examples, the time periods correspond to successive minutes of the media signal and the threshold is about five seconds. 
     Also disclosed herein are example systems that include means for detecting watermarks and means for decoding timestamps in respective ones of the watermarks. Such example systems also include means for determining moments of transition between time periods of media containing the watermarks based on the timestamps by: (a) estimating a coarse transition window between two time periods; (b) mapping a prior transition window estimate to the estimate of (a); (c) narrowing to a fine transition window estimate based on an overlap between the estimate of (a) and (b); (d) comparing the estimate of (c) to a threshold; (e) repeating (a) through (d) for successive time periods using the fine transition window estimate of (c) as the prior transition window estimate of (b) until the fine transition window estimate of (c) satisfies the threshold; and (f) establishing the fine transition window estimate as an established moment of transition between time periods when the estimate of (c) satisfies the threshold. 
     In some example systems, the means for determining is to identify the moments of transition between time periods of the media signal based on the established moment of transition. 
     In some example systems, the time periods correspond to successive minutes of the media signal and the threshold is about five seconds. 
     These and other example methods, apparatus, systems and articles of manufacture (e.g., physical storage media) to implement improve timestamp transition resolution in watermarks in media are disclosed in greater detail below. 
     As used herein, the term “media” includes any type of content and/or advertisement delivered via any type of distribution medium. Thus, media includes television programming or advertisements, radio programming or advertisements, movies, web sites, streaming media, etc. Further, media includes audio and/or visual (still or moving) content and/or advertisements. 
     Example methods, apparatus, and articles of manufacture disclosed herein monitor media presentations at media devices. Such media devices may include, for example, Internet-enabled televisions, personal computers, Internet-enabled mobile handsets (e.g., a smartphone), video game consoles (e.g., Xbox®, PlayStation®), tablet computers (e.g., an iPad®), digital media players (e.g., a Roku® media player, a Slingbox®, etc.), etc. In some examples, media monitoring information is aggregated to determine ownership and/or usage statistics of media devices, relative rankings of usage and/or ownership of media devices, types of uses of media devices (e.g., whether a device is used for browsing the Internet, streaming media from the Internet, etc.), and/or other types of media device information. In examples disclosed herein, monitoring information includes, but is not limited to, media identifying information (e.g., media-identifying metadata, codes, signatures, watermarks, and/or other information that may be used to identify presented media), application usage information (e.g., an identifier of an application, a time and/or duration of use of the application, a rating of the application, etc.), and/or user-identifying information (e.g., demographic information, a user identifier, a panelist identifier, a username, etc.). 
     Audio watermarking is a technique used to identify media such as television broadcasts, radio broadcasts, advertisements (television and/or radio), downloaded media, streaming media, prepackaged media, etc. Existing audio watermarking techniques identify media by embedding one or more audio codes (e.g., one or more watermarks), such as media identifying information and/or an identifier that may be mapped to media identifying information, into an audio and/or video component. In some examples, the audio or video component is selected to have a signal characteristic sufficient to hide the watermark. As used herein, the terms “code” or “watermark” are used interchangeably and are defined to mean any identification information (e.g., an identifier) that may be inserted or embedded in the audio or video of media (e.g., a program or advertisement) for the purpose of identifying the media or for another purpose such as tuning (e.g., a packet identifying header). To identify watermarked media, the watermark(s) are extracted and used to access a table of reference watermarks that are mapped to media identifying information. 
     Unlike media monitoring techniques based on codes and/or watermarks included with and/or embedded in the monitored media, fingerprint or signature-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. 
     As noted above, watermarks can be embedded or otherwise included in media to enable additional information to be conveyed with the media. This information can include timestamps that indicate the time at which a portion of the media signal containing the watermark was broadcast. Timestamps are important for advertisers, for example, to verify the broadcast of their content. Timestamps are also important in media monitoring to identify the moments in time an audience member was exposed to particular media. 
     The timestamps embedded in watermarks change with the time of day and with a given time resolution. Thus, a timestamp at one minute may be T1 and the next minute may be T2 (e.g., T1 plus one minute). Comparing one watermark to the next would indicate when the time switched from T1 to T2. However, at times the watermarks cannot be detected based on, for example, noise obscuring the media signal. Thus, many watermarks go undetected. When two detected timestamps indicate a change in time from T1 to T2 but there are undetected watermarks in between the two watermarks, the analysis will not indicate precisely when the time changed from T1 to T2. Though timestamps that are encoded in watermarks may be accurate to the second, traditional systems only have a time transition window resolution of one minute. That is, known systems can only estimate a time change in increments of one minute. 
     Examples disclosed herein improve the time transition window resolution. For example, in a media signal in which the timestamp code is repeated every 4.8 seconds, there are twelve to thirteen opportunities to detect the timestamp per minute. As disclosed herein, the resolution of the time transition window estimate is improved to, for example, about five seconds. As used herein, “about” means+/−0.2 seconds. This improvement provides more accurate estimation of broadcast time and more valuable information. For example, some advertisements are included in broadcast slots or spots of less than a minute including, for example, ten-second, fifteen-second, or thirty-second spots. When the timestamp transition resolution is only precise to a minute, the exact timing of a sub-minute long broadcast cannot be determined accurately based on such known watermarks. 
     Turning to the figures, a block diagram of an example media monitoring system  100  implementing improved timestamp transition resolution from watermarks in media signals as disclosed herein is illustrated in  FIG.  1   . The example media monitoring system  100  of  FIG.  1    supports monitoring of media presented at one or more monitored sites, such as an example monitored site  105  illustrated in  FIG.  1   . The monitored site  105  includes an example media device  110 , which is also referred to herein as a media presentation device  110 . Although the example of  FIG.  1    illustrates one monitored site  105  and one media device  110 , improved timestamp transition resolution from watermarks in media signals as disclosed herein can be implemented in media monitoring systems  100  supporting any number of monitored sites  105  having any number of media devices  110 . 
     The media monitoring system  100  of the illustrated example includes an example media device meter  125  (also referred to as a meter  125 , a site meter  125 , a site unit  125 , a home unit  125 , a portable device  125 , etc.) to monitor media presented by the media device  110 . In the illustrated example, the media monitored by the media device meter  125  can correspond to any type of media presentable by the media device  110 . For example, monitored media can correspond to media content, such a television programs, radio programs, movies, Internet video, video-on-demand, etc., as well as commercials, advertisements, etc. In the illustrated example, the media device meter  125  determines metering data including timestamps that may identify and/or be used to identify media presented by the media device and the corresponding times (and, thus, infer media exposure) at the monitored site  105 . The media device meter  125  then stores and reports this metering data via an example network  135  to an example data processing facility  140 . The data processing facility  140  performs any appropriate post-processing of the metering data to, for example, determine audience ratings information, identify targeted advertising to be provided to the monitored site  105 , etc. In the illustrated example, the network  135  can correspond to any type(s) and/or number of wired and/or wireless data networks, or any combination thereof. 
     In the illustrated example, the media device  110  monitored by the media device meter  125  can correspond to any type of audio, video and/or multimedia presentation device capable of presenting media audibly and/or visually. For example, the media device  110  can correspond to a television and/or display device that supports the National Television Standards Committee (NTSC) standard, the Phase Alternating Line (PAL) standard, the Systéme Electronique pour Couleur avec Mémoire (SECAM) standard, a standard developed by the Advanced Television Systems Committee (ATSC), such as high definition television (HDTV), a standard developed by the Digital Video Broadcasting (DVB) Project, etc. As other examples, the media device  110  can correspond to a multimedia computer system, a personal digital assistant, a cellular/mobile smartphone, a radio, a tablet computer, etc. 
     In the media monitoring system  100  of the illustrated example, the media device meter  125  and the data processing facility  140  cooperate to perform media monitoring based on detected media watermarks. Moreover, the media device meter  125  implements improved timestamp transition resolution as disclosed herein. Examples of watermarks include identification codes, ancillary codes, etc., that may be transmitted within media signals. For example, identification codes can be transmitted as watermarked data embedded or otherwise included with media (e.g., inserted into the audio, video, or metadata stream of media) to uniquely identify broadcasters and/or media (e.g., content or advertisements). Watermarks can additionally or alternatively be used to carry other types of data, such as copyright protection information, secondary data (e.g., such as one or more hyperlinks pointing to secondary media retrievable via the Internet and associated with the primary media carrying the watermark), commands to control one or more devices, etc. Watermarks are typically extracted using a decoding operation. 
     In the illustrated example of  FIG.  1   , the media device meter  125  is implemented by a portable device including an example watermark detector  145  and an example timestamp transition resolution enhancer  150 . In the illustrated example, the watermark detector  145  is configured to detect watermark(s) in media signal(s) output from a monitored media device, such as the example media device  110 . In the illustrated example, the timestamp transition resolution enhancer  150  is configured to improve the timestamp transition resolution of the watermarks detected by the watermark detector  145 . In some examples, the media device meter  125  corresponds to a special purpose portable device constructed to implement the example watermark detector  145  and the example timestamp transition resolution enhancer  150 . In other examples, the media device meter  125  corresponds to any portable device capable of being adapted (via hardware changes, software changes, firmware changes, or any combination thereof) to implement the example watermark detector  145  and the example timestamp transition resolution enhancer  150 . As such, the media device meter  125  can be implemented by a smartphone, a tablet computer, a handheld device, a wrist-watch type device (e.g., a smart watch such as the Apple Watch sold by Apple Inc.), other wearable devices, a special purpose device, etc. In some examples, the media device meter  125  can be implemented by a portable device that, although portable, is intended to be relatively stationary. Furthermore, in some examples, the media device meter  125  can be implemented by, or otherwise included in, the media device  110 , such as when the media device  110  corresponds to a portable device (e.g., a smartphone, a tablet computer, a handheld device, etc.) capable of presenting media. This latter implementation can be especially useful in example scenarios in which a media monitoring application is executed on the media device  110  itself, but the media device  110  prevents, e.g., via digital rights management or other techniques, third-party applications, such as the media monitoring application, from accessing protected media data stored on the media device  110 . An example implementation of the media device meter  125  is illustrated in  FIG.  3   , which is described in further detail below. Though described as incorporated with the media device meter  125 , the timestamp transition resolution enhancer  150  may be incorporated additionally or alternatively with the data processing facility  140 . Furthermore, in some examples, the media device meter  125  may additionally collect signatures. 
       FIG.  2    illustrates an example watermark  200  that the example media device meter  125  may be configured to detect. The watermark  200  of the illustrated is embedded or otherwise included in media to be presented by media device(s), such as the example media device  110 . For example, the watermark  200  may be embedded in an audio portion (e.g., an audio data portion, an audio signal portion, etc.) of the media, a video portion (e.g., a video data portion, a video signal portion, etc.) of the media, or a combination thereof. The example watermark  200  of  FIG.  2    includes an example first group of symbols  205  and an example second group of symbols  210 . In the illustrated example of  FIG.  2   , the first group of symbols  205  is repeated in successive watermarks  200  embedded/included in the media, whereas the second group of symbols  210 , which is indicative of a broadcast time, differs between successive watermarks  200  embedded/included in the media. 
     In the example watermark of  FIG.  2   , the first group of symbols  205  conveys media identification data (e.g., a media identifier) identifying the media watermarked by the watermark  200 . For example, the media identification data conveyed by the first group of symbols  205  may include data identifying a broadcast station providing the media, a name (e.g., program name) of the media, a source (e.g., a website) of the media, etc. Thus, in the illustrated example of  FIG.  2   , the first group of symbols  205  is also referred to as a first group of media identification symbols  205  (or simply the media identification symbols  205 ). Furthermore, the media identification data conveyed by the first group of symbols  205  (e.g., the media identification symbols  205 ) is repeated in successive watermarks  200  embedded/included in the media. 
     In some examples, the first group of symbols  205  of the watermark  200  includes example marker symbols  215 A-B to assist the watermark detector  145  in detecting the start of the watermark  200  in the watermarked media, and example data symbols  220 A-F to convey the media identification data. Also, in some examples, corresponding symbols pairs in similar respective locations after the first marker symbol  215 A and the second marker symbol  215 B are related by an offset. For example, the value of data symbol  220 D may correspond to the value of data symbol  220 A incremented by an offset, the value of data symbol  220 E may correspond to the value of data symbol  220 B incremented by the same offset, and the value of data symbol  220 F may correspond to the value of data symbol  220 C incremented by the same offset, as well. In such examples, the symbols pairs  220 A/D,  220 B/E and  220 C/F are referred to as symbol offset pairs, or offset pairs, and the offset used to generate the symbol offset pairs forms an additional data symbol that can be used to convey the media identification data. 
     In the example watermark  200  of  FIG.  2   , the second group of symbols  210  conveys timestamp data (e.g., a timestamp) identifying, for example, a particular elapsed time within the watermarked media. Thus, in the illustrated example of  FIG.  2   , the second group of symbols  210  is also referred to as the second group of timestamp symbols  210  (or simply the timestamp symbols  210 ). Furthermore, the timestamp data conveyed by the second group of symbols  210  (e.g., the timestamp symbols  210 ) differs in successive watermarks  200  embedded/included in the media (e.g., as the elapsed time of the watermarked media increases with each successive watermark  200 ). 
     In the illustrated example of  FIG.  2   , the watermark  200  is embedded/included in the desired media at a repetition interval of t seconds (or, in other words, at a repetition rate of 1/t seconds), with the first group of symbols  205  remaining the same in successive watermarks  200 , and the second group of symbols  205  varying in successive watermarks  200  according to the time resolution supported by the symbols  205 . For example, the symbols  205  may support a time resolution of one minute and, thus, will change on one minute boundaries. For example, the repetition interval t may correspond to t=4.8 seconds. As there are twelve symbols in the example watermark  200  (e.g., eight symbols in the first group of symbols  205  and four symbols in the second group of symbols  210 ) each watermark symbol in the illustrated example has a duration of 4.8/12=0.4 seconds. However, other values for the repetition interval t may be used in other examples. 
     In some examples, a watermark symbol included in the watermark  200  is able to take on one of several possible symbol values. For example, if a symbol in the watermark  200  represents four bits of data, then the symbol is able to take on one of sixteen different possible values. For example, each possible symbol value may correspond to a different signal amplitude, a different set of code frequencies, etc. In some such examples, to detect a watermark symbol embedded/included in watermarked media, the example watermark detector  145  processes monitored media data/signals output from the example media device  110  to determine measured values (e.g., signal-to-noise ratio (SNR) values) corresponding to each possible symbol value the symbol may have. The watermark detector  145  then selects the symbol value corresponding to the best (e.g., strongest, largest, etc.) measured value (possibly after averaging across multiple samples of the media data/signal) as the detected symbol value for that particular watermark symbol. 
     An example implementation of the media device meter  125  (e.g., which may be a portable device) of  FIG.  1    is illustrated in  FIG.  3   . In the illustrated example of  FIG.  3   , the media device meter  125  includes one or more example sensor(s)  305  to detect media data/signal(s) emitted or otherwise output by the example media device  110 . In some examples, the sensor(s)  305  include an audio sensor to monitor audio data/signal(s) output by the media device  110 . Such an audio sensor may be implemented using any type of audio sensor or audio interface, such as a microphone, a transducer, a cable/wire, etc., capable of receiving and processing audio signals (e.g., such as in the form of acoustic and/or electrical signals). Additionally or alternatively, in some examples, the sensor(s)  305  include a video sensor to monitor video data/signal(s) output by the media device  110 . Such a video sensor may be implemented using any type of video sensor or video interface, such as a camera, a light detector, a cable/wire, etc., capable of receiving and processing video signals (e.g., such as in the form of optical images and/or electrical signals). 
     The example media device meter  125  of  FIG.  3    also includes the example watermark detector  145 . In the illustrated example of  FIG.  3   , the watermark detector  145  is configured to detect watermarks, such as the example watermark  200  of  FIG.  2   , in the media data/signal(s) detected by the example sensor(s)  305 . In some examples, the watermark detector  145  of  FIG.  3    is structured to process audio data/signal(s) obtained by the sensor(s)  305  to detect symbols of instances of the watermark  200  that are encoded in one or more frequencies of the sensed audio data/signal(s), or otherwise encoded in the frequency domain of the sensed audio data/signal(s). Examples of encoding watermarks in the frequency domain of an audio signal, and corresponding example watermark detection techniques that may be implemented by the example watermark detector  145 , are described in U.S. Pat. No. 8,359,205, entitled “Methods and Apparatus to Perform Audio Watermarking and Watermark Detection and Extraction,” which issued on Jan. 22, 2013, U.S. Pat. No. 8,369,972, entitled “Methods and Apparatus to Perform Audio Watermarking Detection and Extraction,” which issued on Feb. 5, 2013, U.S. Publication No. 2010/0223062, entitled “Methods and Apparatus to Perform Audio Watermarking and Watermark Detection and Extraction,” which was published on Sep. 2, 2010, U.S. Pat. No. 6,871,180, entitled “Decoding of Information in Audio Signals,” which issued on Mar. 22, 2005, U.S. Pat. No. 5,764,763, entitled “Apparatus and Methods for Including Codes in Audio Signals and Decoding,” which issued on Jun. 9, 1998, U.S. Pat. No. 5,574,962, entitled “Method and Apparatus for Automatically Identifying a Program Including a Sound Signal,” which issued on Nov. 12, 1996, U.S. Pat. No. 5,581,800, entitled “Method and Apparatus for Automatically Identifying a Program Including a Sound Signal,” which issued on Dec. 3, 1996, U.S. Pat. No. 5,787,334, entitled “Method and Apparatus for Automatically Identifying a Program Including a Sound Signal,” which issued on Jul. 28, 1998, and U.S. Pat. No. 5,450,490, entitled “Apparatus and Methods for Including Codes in Audio Signals and Decoding,” which issued on Sep. 12, 1995, all of which are hereby incorporated by reference in their entireties. U.S. Pat. Nos. 8,359,205, 8,369,972, U.S. Publication No. 2010/0223062, U.S. Pat. Nos. 6,871,180, 5,764,763, 5,574,962, 5,581,800, 5,787,334, and 5,450,490 describe example watermarking systems in which a watermark is included in an audio signal by manipulating a set of frequencies of the audio signal. 
     In some examples, the watermark detector  145  of  FIG.  3    is structured to process audio data/signal(s) obtained by the sensor(s)  305  to detect symbols of instances of the watermark  200  that are encoded in one or more time domain characteristics of the sensed audio signal, such as by modulating the amplitude and/or phase of the audio signal in the time domain. Examples of encoding watermarks in the time domain of an audio signal, and corresponding example watermark detection techniques that may be implemented by the example watermark detector  145 , include, but are not limited to, examples in which spread spectrum techniques are used to include a watermark in an audio signal. For example, such a watermark can be encoded in the audio signal by (1) spreading the watermark by modulating the watermark with a pseudo-noise sequence and then (2) combining the spread watermark with the audio signal. Detection of such a watermark involves correlating the audio signal (after being watermarked) with the pseudo-noise sequence, which de-spreads the watermark, thereby permitting the watermark to be detected after the correlation. 
       FIG.  4    illustrates an example mapping  400  of segments of a media signal over time. The first row represents the media segments  405 ( 01 - 41 ) during which a watermark  200  is broadcast. In the example mapping  400 , each media segment  405  may have, for example, a duration of five seconds. Thus, there are twelve segments in one minute of a media broadcast. In other examples, other media segment durations may be used including, for example, 4.8 seconds and/or any other desired amount. The “X” in the second row represents the watermarks  200  detected by the watermark detector  145 . In this example, the watermark detector  145  detects eighteen watermarks  200 . Some of the media segments  405  are not associated with a detected watermark. In such examples, the signal may have been obscured by, for example, noise, and the watermark detector  145  may not have been able to detect an associated watermark. 
     As shown in  FIG.  3   , the example media device meter  125  also includes an example timestamp decoder  310 . The timestamp decoder  310  reads the timestamp symbols  210  from the watermark  200  detected by the watermark detector  145 . The time indicated by the timestamp symbols  210  is associated with the media broadcast with which the detected watermark  200  is broadcast. In the example mapping  400  of  FIG.  4   , the timestamp decoder  310  having read the timestamps in the watermarks  200 , determines that the time is T−1 in the second detected watermark  200  of the third media segment  405 ( 03 ). In the third detected watermark  200  of the seventh media segment  405 ( 07 ), the timestamp is T. The timestamp reads as time T until the timestamp decoder  310  determines the time is T+1 at the seventh detected watermark  200  of the eighteenth media segment  405 ( 18 ). The detection and decoding process continues throughout operation of the media device meter  125 . In the example shown, a time change to T+2 is detected at the thirteenth detected watermark  200  of the thirty-first media segment  405 ( 31 ), and a time change to T+3 is detected at the seventeenth detected watermark  200  of the fortieth media segment  405 ( 40 ). 
     With the information available from the watermark detector  145  and the timestamp decoder  310 , the media device meter  125  and/or data processing facility  400  can determine estimated transition windows or coarse transitions windows indicative of when the time of the media broadcast for the associated media segment  405  advanced to the next time unit (e.g., next minute of the day). For example, the media device includes the timestamp transition resolution enhancer  150  which has an example transition window estimator  315 . The transition window estimator  315  determines the estimated transition window based on a difference between two detected watermarks. As shown in  FIG.  4   , the time of the media broadcast is T−1 for the third media segment  405 ( 03 ). At the seventh media segment  405 ( 07 ), the detected watermark  200  indicates that the time of the broadcast is T. Thus, the time changed from T−1 to T in between the broadcast of the third media segment  405 ( 03 ) and the seventh media segment  405 ( 07 ). As shown in  FIG.  4   , there are several media segments  405 ( 04 - 06 ) between the media segments  405  associated with the different watermarks  200 . In this example, these three media segments  405 ( 04 - 06 ) lack detected watermarks due to, for example, obfuscations from noise. Thus, it is not known when exactly the time period switched between T−1 and T. This could have occurred immediately after the third media segment  405 ( 03 ) was broadcast up until the seventh media segment  405 ( 07 ) was broadcast. Thus, there is a window of time during which the time transition occurred. In this example, the transition window estimator  315  determines a first estimated transition window  410  between time T−1 and T. 
     The example timestamp transition resolution enhancer  150  also includes an example resolution comparator  320 . The resolution comparator  320  compares the duration of a transition window to a threshold to determine if the duration of the transition window meets the threshold. The threshold establishes the desired resolution of the timestamp transition. In the example where the media segments  405  of  FIG.  4    have a five second duration, the first estimated transition window  410  is shown as twenty seconds. That is, the time switched from T−1 to T sometime during those twenty seconds. The resolution comparator  320  compares the time period of twenty seconds to a threshold which may be set, for example, at five seconds. That is, in this example, a timestamp transition resolution of five seconds is desired. In other examples, the threshold is any desirable level of resolution. In this example, the twenty second duration of the first estimated transition window  410  does not meet the threshold of five seconds. Thus, the timestamp transition resolution enhancer  150  continues operation to improve the resolution of the time transition window. If the first estimated transition window  410  does meet the threshold, the timestamp transition resolution enhancer  150  sets the first estimated transition window  410  as the established time transition or the baseline moment of transition. 
     During continued operation, the example transition window estimator  315  determines subsequent time transitions and the corresponding transition windows. In the illustrated example, the example transition window estimator  315  determines a second estimated transition window  415  between the detection of time T at the sixth detected watermark  200  of the thirteenth media segment  405 ( 13 ) and time T+1 at the seventh detected watermark  200  of the eighteenth media segment  405 ( 18 ). In this example, the second estimated transition window  415  is twenty-five seconds long, which is longer in duration than the first estimated transition window  410  and, therefore, alone does not improve the timestamp transition resolution. 
     The timestamp transition resolution enhancer  150  also includes an example mapper  325  that aligns or maps a reference transition window with an estimated transition window. For example, when the resolution comparator  320  determines that an estimated transition window does not meet the threshold, the mapper  320  uses the estimated transition window as a reference transition window and maps or aligns the reference transition window with a subsequent estimated transition window. A first estimated transition window can be used to predict subsequent estimated transition windows because the transitions between time periods is cyclical. A second estimated transition window and the first estimated transition window (used as a reference transition window) can be used to refine or improve the estimate of the timestamp transition. 
     In the example of  FIG.  4   , the first estimated transition window  410  has a duration of twenty seconds. When the media segments  405  are of a five second duration, there are twelve segments in a minute. Thus, the first transition window  410  would indicate subsequent transition windows every minute or twelve media segments  405 . Thus, in this example, the first transition window  410  is used by the mapper  325  to predict, or estimate, a first reference transition window  420  by mapping the first estimated transition window  410  down twelve media segments  405  to form the first reference transition window  420  in alignment with the second estimated transition window  415 . More specifically, in the example mapping  400  of  FIG.  4   , the first estimated transition window  410  appears between the third and sixth media segments  405 ( 03 - 06 ). When the first estimated transition window  410  is mapped down (in this example one minute), the next estimate for a window transition or the first reference transition window  420  appears twelve media segments later or the fifteenth media segment  405 ( 15 ) to the eighteenth media segment  405 ( 18 ). 
     Based on the second estimated transition window  415 , the timestamp transition resolution enhancer  150  can determine that a change in the time period occurred between the watermark  200  detected in the thirteenth media segment  405 ( 13 ) and the watermark  200  detected in the seventeenth media segment  405 ( 17 ). However, the mapping of the first estimated transition window  410  as the first reference transition window  420  shows that the change in the time period occurred during one of the fifteenth to eighteenth media segments  405 ( 15 - 18 ). With these two estimates, the mapper  325  determines that the change in the time period between T and T+1 occurred during the intersection of these two windows, namely, during the media segments  405 ( 15 - 17 ) that overlap, or intersect, between the second estimated transition window  415  and the first reference transition window  420 , which forms a first mapped transition window  425 . Compared to the coarser first estimated transition window  410  and second estimated transition window, the first mapped transition window  425  represents a fine transition window in which the transition resolution has been improved. 
     The resolution comparator  320  compares the first mapped transition window  425  to the threshold. If the first mapped transition window meets the threshold, the timestamp transition resolution enhancer  150  sets the first mapped transition window  425  as the established time transition or the baseline moment of transition. In the example of  FIG.  4   , the first mapped transition window  425  has a duration of fifteen seconds and fails to meet the threshold of five seconds. 
     If a desired level of resolution is not met, the timestamp transition resolution enhancer  150  continues operation to improve the resolution of the time transition window, which includes repetition of one or more of the operations identified above. For example, in the illustrated example, the example transition window estimator  315  determines a third estimated transition window  430  between the detection of time T+1 at the twenty-sixth media segment  405 ( 26 ) and time T+2 at the thirty-first media segment  405 ( 31 ). In this example, the third estimated transition window  430  is twenty-five seconds long, which is longer in duration than the first mapped transition window  425  and, therefore, alone does not improve the timestamp transition resolution. 
     The mapper  325  uses the first mapped transition window  425 , to predict, or estimate, a second reference transition window  435  and aligns or maps the second reference transition window  435  with the third estimated transition window  430 . In this example, the first mapped transition window  425  occurs during the fifteenth, sixteenth, or seventeenth media segments  405 ( 15 - 17 ). When mapped over an additional time period (e.g., a minute) as the second reference transition window  435 , the duration for a subsequent timestamp transition is during the twenty-seventh, twenty-eight, or twenty-ninth media segment  405 ( 27 - 29 ). 
     Based on the third estimated transition window  415 , the timestamp transition resolution enhancer  150  can determine that a change in the time period occurred between the twenty-sixth and thirtieth media segments  405 ( 26 - 30 ). However, the mapping of the first mapped transition window  425  as the second reference transition window  435  shows that the change in the time period occurred during the twenty-seventh, twenty-eight, or twenty-ninth media segment  405 ( 27 - 29 ). With these two estimates, the mapper  325  determines that the change in the time period between T+1 and T+2 occurred during the media segments  405  that overlap between the third estimated transition window  430  and the second reference transition window  435 , which forms the second mapped transition window  440 . 
     The resolution comparator  320  compares the second mapped transition window  440  to the threshold. If the second mapped transition window  440  meets the threshold, the timestamp transition resolution enhancer  150  sets the second mapped transition window  440  as the established time transition or the baseline moment of transition. In the example of  FIG.  4   , because the first mapped transition window  435  is wholly overlapped by the third estimated transition window  430 , there is no further improvement to the transition window resolution. Specifically, in this example, the transition window remains fifteen seconds and fails to meet the threshold of five seconds. 
     As noted above, when a desired level of resolution is not met, the timestamp transition resolution enhancer  150  continues operation to improve the resolution of the time transition window. For example, in the illustrated example, the example transition window estimator  315  determines a fourth estimated transition window  445  between the detection of time T+2 at the thirty-first media segment  405 ( 31 ) and time T+3 at the fortieth media segment  405 ( 40 ). In this example, the fourth estimated transition window  445  is fifteen seconds long, which is not shorter in duration than the second mapped transition window  440  and, therefore, alone does not improve the timestamp transition resolution. 
     The mapper  325  uses the second mapped transition window  440  to predict, or estimate, a third reference transition window  450  and aligns or maps the second reference transition window  450  with the fourth estimated transition window  445 . In this example, the second mapped transition window  440  occurs during the twenty-seventh, twenty-eight, or twenty-ninth media segment  405 ( 27 - 29 ). When mapped over an additional time period (e.g., a minute) as the third reference transition window  450 , the duration of the subsequent timestamp transition is during the thirty-ninth, fortieth, and forty-first media segments  405 ( 39 - 41 ). 
     Based on the fourth estimated transition window  445 , the timestamp transition resolution enhancer  150  can determine that a change in the time period occurred between the thirty-seventh and thirty-ninth media segments  405 ( 37 - 39 ). However, the mapping of the second mapped transition window  440  as the third reference transition window  450  shows that the change in the time period occurred during the thirty-ninth, fortieth, and forty-first media segments  405 ( 39 - 41 ). With these two estimates, the mapper  325  determines that the change in the time period between T+2 and T+3 occurred during the media segment  405  that overlaps, or intersects, between the fourth estimated transition window  445  and the third reference transition window  450 , which forms the third mapped transition window  455 . In this example, the third mapped transition window  455  is the thirty-ninth media segment  405 ( 39 ). 
     The resolution comparator  320  compares the third mapped transition window  455  to the threshold. If the third mapped transition window  455  does not meet the threshold, the timestamp transition resolution enhancer continues through these operations to continue to improve the resolution. If the third mapped transition window  455  meets the threshold, the timestamp transition resolution enhancer  150  sets the third mapped transition window  455  as the established time transition or the baseline moment of transition  460 . In the example of  FIG.  4   , the third mapped transition window  450  has a duration of five seconds and meets the threshold. 
     When a moment of time transition that meets the threshold is achieved, the established time transition  460  is determined. The established time transition  460  is stored in a database  330  in the media device meter  125 , for example. The database  330  may be used for storage and retrieval of some or all data disclosed herein including, for example, data from the sensor(s)  305 , the watermarks  200 , the estimated transition windows  410 ,  415 ,  430 ,  445 , the reference transition windows  420 ,  435 ,  450 , and the mapped transition windows  425 ,  440 ,  455 . 
     When the established time transition  460  is determined, the timestamp transition resolution enhancer  150  retroactively maps prior time transitions in the media signal and/or proactively maps subsequent transitions in the media signal based on the established time transition  460 . For example, in the mapping  400  of  FIG.  4   , the established time transition  460  is set at the thirty-ninth media segment  405 ( 39 ). Thus, the transition between time period T+2 and time period T+3 occurred during the thirty-ninth media segment  405 ( 39 ). One unit of the time measurement divided into the media segments can be used to accurately locate the prior time transition, i.e., the transition between time period T+1 and T+2. In the example of  FIG.  4   , where the unit of time measurement is one minute and there are five second segments, the timestamp transition resolution enhancer  150  counts back twelve segments and determines that the established transition  460  between time T+1 and time T+2 occurred during the twenty-seventh media segment  405 ( 27 ). Similarly, the timestamp transition resolution enhancer  150  determines that the established time transition  460  between time T and time T+1 occurred during the fifteenth media segment  405 ( 15 ), and the established time transition  460  between time T−1 and time T occurred during the third media segment  405 ( 03 ). 
     In some examples, the timestamp transition resolution enhancer  150  implements a voting scheme to assess the value of data. In this example, the timestamp transition resolution enhancer  150  discards data indicative of errors. For example, data showing a decrease in a time value, data between watermarks of consecutive media segments showing a missed time unit (e.g., a skipped minute), and other erroneous or questionable data can be ignored. 
     While an example manner of implementing the media device meter  125  of  FIG.  1    is 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 watermark detector  145 , the example timestamp transition resolution enhancer  150 , the example sensor(s)  305 , the example timestamp decoder  310 , the example transition window estimator  315 , the example resolution comparator  320 , the example mapper  325 , the example databased  330 , and/or, more generally, the example media device meter  125  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 watermark detector  145 , the example timestamp transition resolution enhancer  150 , the example sensor(s)  305 , the example timestamp decoder  310 , the example transition window estimator  315 , the example resolution comparator  320 , the example mapper  325 , the example databased  330 , and/or, more generally, the example media device meter  125  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, watermark detector  145 , the example timestamp transition resolution enhancer  150 , the example sensor(s)  305 , the example timestamp decoder  310 , the example transition window estimator  315 , the example resolution comparator  320 , the example mapper  325 , the example databased  330 , and/or the example media device meter  125  is/are hereby expressly defined to include a non-transitory 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. including the software and/or firmware. Further still, the example media device meter  125  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. 
     A flowchart representative of example machine readable instructions for implementing the media device meter  125  of  FIG.  3    is shown in  FIG.  5   . In this example, the machine readable instructions comprise a program for execution by a processor such as the processor  1012  shown in the example processor platform  1000  discussed below in connection with  FIG.  6   . The program may be embodied in software stored on a non-transitory 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  1012 , but the entire program and/or parts thereof could alternatively be executed by a device other than the processor  1012  and/or embodied in firmware or dedicated hardware. Further, although the example program is described with reference to the flowchart illustrated in  FIG.  5   , many other methods of implementing the example media device meter  125  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. Additionally or alternatively, any or all of the blocks may be implemented by one or more hardware circuits (e.g., discrete and/or integrated analog and/or digital circuitry, a Field Programmable Gate Array (FPGA), an Application Specific Integrated circuit (ASIC), a comparator, an operational-amplifier (op-amp), a logic circuit, etc.) structured to perform the corresponding operation without executing software or firmware. 
     As mentioned above, the example processes of  FIG.  5    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. “Including” and “comprising” (and all forms and tenses thereof) are used herein to be open ended terms. Thus, whenever a claim lists anything following any form of “include” or “comprise” (e.g., comprises, includes, comprising, including, etc.), it is to be understood that additional elements, terms, etc. may be present without falling outside the scope of the corresponding claim. 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” and “including” are open ended. 
     The example machine readable instructions  500  of  FIG.  5    begin at block  505  when the watermark detector  145  detects one or more watermarks  200  from a media signal. The example timestamp decoder  310  decodes a timestamp (Tn) from the watermarks (block  510 ) (in some examples n is initially set at 0). For example, the timestamp decoder  310  reads timestamps such as timestamp symbols  210  from the watermark  200 . The example timestamp decoder  310  analyzes a media signal to detect and monitor subsequent watermarks and timestamps (block  515 ). The example timestamp transition resolution enhancer  150  determines if a watermark includes a timestamp indicative of a change in time (Tn+1) (block  520 ). For example, the watermark  200  includes time symbols  210  that indicate the time at which the watermark  200  and associated media content was broadcast. As the time of day progresses, the time symbols  210  change. Eventually, a subsequent watermark  200  will include a timestamp that indicates a change of time from (Tn) to (Tn+1). 
     If a watermark  200  does not include a timestamp indicative of a change in time (block  520 ), the example timestamp decoder  310  continues to detect and decode watermarks and timestamps (block  515 ). However, if a watermark  200  does include a timestamp indicative of change in time (block  520 ), the example transition window estimator  315  of the example timestamp transition resolution enhancer  150  identifies an estimated transition window (Wn) (block  525 ). For example, the transition window estimator  315  determines a duration of time or time window during which the time changed from one time period to a second time period based on the duration between the two watermarks with disparate timestamps. As disclosed in the example above, the transition window estimator  315  determines the first estimated transition window  410 . 
     The example resolution comparator  320  of the example timestamp transition resolution enhancer  150  determines if the estimated transition window (Wn) meets or satisfies a threshold time duration (block  530 ). In some examples, the threshold is set at five seconds, though other values may be used. If the estimated transition window (Wn) is five seconds or less, in this example, the resolution comparator  320  will determine that the threshold is met. In other words, the desired resolution of estimating when a time transition occurred has been satisfied. When the estimated transition window (Wn) is determined to meet the threshold (block  530 ), the example timestamp transition resolution enhancer  150  continues and sets the estimated transition window (Wn) as the moment of time transition (block  535 ). 
     When the moment of time transition is set (block  535 ), the example timestamp transition resolution enhancer  150  retroactively and/or proactively sets prior and/or subsequent moments of time transitions (block  540 ). For example, the timestamp transition resolution enhancer  150  sets the established moment of time transition  460  when the resolution threshold is met. Once a moment of time transition is established with the desired resolution, other moments of time transition can be determined based on the number of media segments in a time unit. In the example disclosed above, there are five second media segments and, therefore, twelve segments in a minute. When the threshold of five seconds (e.g., one media segment) is met, the timestamp transition resolution enhancer  150  sets the moment of time transition  460  and can count forward and/or backward twelve media segments to mark or otherwise note moments of other time transitions. When the moments of time transition are marked to the desired resolution level, the example program  500  ends. 
     When the estimated transition window (Wn) does not meet the threshold time duration (block  530 ), the example timestamp transition resolution enhancer  150  continues and sets the estimated transition window (Wn) as a reference transition window (block  545 ). For example, the timestamp transition resolution enhancer  150  sets the first estimated transition window  410  as the first referenced transition window  420  when the first estimated transition window  410  fails to meet the threshold. 
     The example timestamp decoder  310  and the example timestamp transition resolution enhancer  150  continue and analyze the media signal to detect and monitor subsequent watermarks and timestamps (block  550 ) to detect a watermark including a timestamp indicative of a change in time (Tn+2) (block  555 ). If a watermark  200  does not include a timestamp indicative of a change in time (block  555 ), the example timestamp transition resolution enhancer  150  continues to detect and decode watermarks and timestamps (block  550 ). However, if a watermark  200  does include a timestamp indicative of change in time (block  555 ), the example timestamp transition resolution enhancer  150  identifies an estimated transition window (Wn+1) (block  560 ). For example, the transition window estimator  315  determines a duration of time or time window during which the time changes from a second time period to a third time period based on the duration between the two watermarks with disparate timestamps. As disclosed in the example above, the transition window estimator  315  determines the second estimated transition window  415 . 
     Though not explicitly shown in  FIG.  5   , in some examples, the example timestamp transition resolution enhancer  150  determines if the estimated transition window between the second time period and the third time period meets the threshold similar to block  530 . If the threshold is met, the example program would continue through blocks  535  and  540  as detailed above. 
     When the estimated transition window (Wn+1) is determined (block  560 ), and the estimated transition window (Wn+1) fails to meet the threshold or is not compared to the threshold, the example mapper  325  of the example timestamp transition resolution enhancer  150  maps or aligns the reference transition window (Wn) with the estimated transition window (Wn+1) (block  565 ). For example, the mapper  325  maps the first estimated transition window  410  as the first reference transition window  420  to the second estimated transition window  415 . The example timestamp transition resolution enhancer  150  determines an overlap between the reference transition window (Wn) and the estimated transition window (Wn+1) (block  570 ). For example, the timestamp transition resolution enhancer  150  determines what media segments  405 ( 15 - 17 ) overlap between the media segments  405 ( 15 - 18 ) broadcast during the duration of the first reference transition window  420  and the media segments  405 ( 13 - 17 ) broadcast during the duration of the second estimated transition window  415 . The example timestamp transition resolution enhancer  150  sets the overlap as the mapped transition window (block  575 ). In the example disclosed above, the timestamp transition resolution enhancer  150  sets the overlap between the second estimated transition window  415  and the first reference transition window  420  as the first mapped transition window  425 . In another example, the timestamp transition resolution enhancer  150  sets the overlap between the fourth estimated transition window  445  and the third reference transition window  450  as the third mapped transition window  455 . 
     The example resolution comparator  320  of the example timestamp transition resolution enhancer  150  determines if the mapped transition window meets a threshold time duration (block  580 ). In some examples, the threshold is set at five seconds, though other values may be used. If the mapped transition window is five seconds or less, in this example, the resolution comparator  320  will determine that the threshold is met. In other words, the desired resolution of estimating when a time transition occurred has been satisfied. When the mapped transition window is determined to meet the threshold (block  580 ), the example timestamp transition resolution enhancer  150  continues and sets the mapped transition window as the moment of time transition (block  585 ). In one of the examples disclosed above, the resolution comparator  320  determines that the third mapped transition window  455  meets the threshold of five seconds. The timestamp transition resolution enhancer  150  sets the third mapped transition window  455  as the established time transition  460 . 
     When the moment of time transition is set (block  585 ), the example timestamp transition resolution enhancer  150  retroactively and/or proactively sets prior and/or subsequent moments of time transitions (block  540 ), as disclosed above. For example, the timestamp transition resolution enhancer  150  sets the established moment of time transitions  460  when the resolution threshold is met for other time transitions during the broadcast of the media signal. When the moments of time transition are marked to the desired resolution level, the example program  500  ends. 
     If the mapped transition window fails to the meet the threshold time duration (block  580 ), the example timestamp transition resolution enhancer  150  sets the mapped transition window as the reference transition window (Wn) (block  590 ). For example, when the first mapped transition window  425  fails to meet the threshold of five seconds, the timestamp transition resolution enhancer  150  sets the first mapped transition window  425  as the second reference transition window  435 . Thereafter, the example timestamp decoder  310  and the example timestamp transition resolution enhancer  150  continue to monitor the media signal and repeating the analysis by returning to block  550 , after incrementing n (block  595 ) to indicate the subsequent time periods being analyzed. 
     The example timestamp decoder  310  and the example timestamp transition resolution enhancer  150  continue execution until it is determined that the duration of the mapped transition window satisfies the threshold setting the desired resolution of a time transition window (block  580 ). When the threshold is satisfied, or the desired resolution is otherwise determined to be met, the example timestamp transition resolution enhancer  150  proceeds through setting the mapped transition window as the moment of time transition (block  585 ) and mapping prior and/or subsequent time transition (block  540 ) as disclosed above until the example program  500  ends. 
       FIG.  6    is a block diagram of an example processor platform  600  structured to execute the instructions of  FIG.  5    to implement the media device meter  125  of  FIG.  3   . The processor platform  600  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  600  of the illustrated example includes a processor  605 . The processor  605  of the illustrated example is hardware. For example, the processor  605  can be implemented by one or more integrated circuits, logic circuits, microprocessors or controllers from any desired family or manufacturer. The hardware processor may be a semiconductor based (e.g., silicon based) device. In this example, the processor  605  implements the example watermark detector  145 , the example timestamp transition resolution enhancer  150 , the example timestamp decoder  310 , the example transition window estimator  315 , the example resolution comparator  320 , and the example mapper  325 . 
     The processor  605  of the illustrated example includes a local memory  610  (e.g., a cache). The processor  605  of the illustrated example is in communication with a main memory including a volatile memory  615  and a non-volatile memory  620  via a bus  625 . The volatile memory  615  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  620  may be implemented by flash memory and/or any other desired type of memory device. Access to the main memory  615 ,  620  is controlled by a memory controller. 
     The processor platform  600  of the illustrated example also includes an interface circuit  630 . The interface circuit  630  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  635  are connected to the interface circuit  630 . The input device(s)  635  permit(s) a user to enter data and/or commands into the processor  605 . The input device(s) 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  640  are also connected to the interface circuit  630  of the illustrated example. The output devices  640  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 printer and/or speakers). The interface circuit  630  of the illustrated example, thus, typically includes a graphics driver card, a graphics driver chip and/or a graphics driver processor. 
     The interface circuit  630  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  645  (e.g., an Ethernet connection, a digital subscriber line (DSL), a telephone line, coaxial cable, a cellular telephone system, etc.). 
     The processor platform  600  of the illustrated example also includes one or more mass storage devices  650  for storing software and/or data. Examples of such mass storage devices  650  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  655  of  FIG.  5    may be stored in the mass storage device  655 , in the volatile memory  615 , in the non-volatile memory  620 , and/or on a removable tangible computer readable storage medium such as a CD or DVD. 
     From the foregoing, it will be appreciated that example methods, apparatus and articles of manufacture have been disclosed that improve or enhance the resolution of a timestamp transition window. Media signals contain watermarks with timestamps indicative of the time of broadcast of the portion of the media signal associated with the watermark. Media content providers and advertisers want to know precisely when their media was broadcast, and the timestamps in the watermarks are used to provide this information. 
     In some prior watermarking solutions, the exact broadcast time of media broadcast in time slots smaller than the transition window will go undetected. For example, a transition window of one minute will not identify exactly when an advertisement with a duration of twenty seconds was broadcast. An advertiser who paid for a twenty second advertisement spot at the beginning of a minute-long advertisement break would want to know that their advertisement was in fact broadcast during the first twenty seconds of the advertisement break. This level of precision cannot be provided when the timestamp transition window is too large. Examples disclosed herein improve the timestamp transition resolution to overcome the limitation of the prior art. In some examples, the resolution is improved to five seconds. The improved resolution enables the exact broadcast times of each moment of the media signal to be pinpointed down to the resolution threshold (e.g., 5 seconds). This improvement has been developed and is usable without requiring the broadcast of additional watermarks, enhanced detection techniques to capture more watermarks, or a more finite segmentation of media signals. 
     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.