# Patent

## Title
Device, system and method for measurement of media consumption in digital media terminals

## Abstract

A device, system and method for enabling the measuring of audiences to media consumed through the use of digital media terminals. An example disclosed herein includes a loop-back device that allows the production/extraction of content identification information from media items rendered by a digital media terminal that can be seamlessly and homogenously implemented in a wide variety of media distribution platforms and devices, including Internet and mobile networks.

## Background
RELATED APPLICATION(S)
This patent arises from a continuation of International Application Serial Number PCT/IB2010/000283, entitled “Device, System and Method For Measurement of Media Consumption in Digital Media Terminals” and filed on Jan. 28, 2010, which claims priority from U.K. Patent Application No. GB 0901445.7, entitled “Device, System and Method For Measurement of Media Consumption in Digital Media Terminals” and filed on Jan. 28, 2009. International Application Serial Number PCT/IB2010/000283 and U.K. Patent Application No. GB 0901445.7 are hereby incorporated by reference in their respective entireties.


FIELD OF THE DISCLOSURE
The present disclosure relates to apparatus and methods for measuring the consumption of media in different types of digital media terminals.
BACKGROUND
The term digital media terminal (hereinafter “DMT”) is used herein to describe any electronic device capable of rendering media (e.g. playing back recorded or broadcasted audio/video) to a user and recording user generated media (e.g. recoding or transmitting audio/video). Digital media terminals can be found today in the markets in various embodiments, including desktop personal computers, laptop devices (such as notebook computers) and handheld devices (such as mobile “smart” phones. Such devices are becoming a preferred way of consuming media by, for example, playing downloaded or streamed audio and video content. Audio clips may range from streamed radio, to a variety of audio podcasts such as news, weather or finance reports, audio books, education, and training podcasts, music podcasts, health services and self-help podcasts, etc. In the specific case of streamed video, also known in the industry as ‘on-line video’, the content may range from short clips lasting a couple of minutes, to full length TV programs which are offered through both traditional broadcasting mechanisms and data networks as well (e.g., Internet). New ways of consuming media are becoming increasingly popular, such as “Web TV” (i.e., live streaming through Internet of TV channels), “Catch-up TV” (i.e., downloading or streaming a TV program which has been broadcasted in traditional broadcasting networks during a previous period of time), and video-on-demand (i.e. downloading or streaming any piece of video content from a catalogue).
These new media consumption trends have opened the way to new advertising markets, and therefore measuring audiences became a need in such markets.
Several methods have been attempted to track and measure this type of on-line audio/video media consumption. One solution currently used by companies that measure Web site traffic relies on software programs running at the video servers generating the video streams (or alternatively at dedicated measurement servers invoked by “tags” included in web pages) that keep track of the exact number of video sessions (also known as “site centric” approach). Such approach usually provides accurate information about media items streamed or downloaded, but provide little (if any) information about actual consumers (e.g. geographical data obtained from IP addresses).
A second approach exists by which a “software meter” is installed in a number of computers participating in a continuous survey in the form of a “panel”. Such software meters are able to detect and log internet activity, mostly in the form of WWW page visits and file downloading (hereinafter “WWW loggers”). Such approach is usually referred to as a ‘user centric’ method, since they measure the actions performed by known individuals (in terms of media consumption) as opposed to measuring activity in servers (where users may not be individualized). User centric methods resemble the methodology used in measurement of television audiences (i.e. it comprises a panel of users who accept to be monitored). WWW loggers usually capture and report many types of interactions of their users with their personal computers and the worldwide web, including streaming video and downloading of files of various kinds. Basically, such approach allows knowing who has seen which websites, for how long and in which order. User centric methods have the advantage of providing precise demographical information about users, although restricted by inherent limitations in terms of panel size and panel balance (i.e. panels must evenly represent the universes they describe, which means that all categories must be proportionally included in the panels).
Many ‘user centric’ solutions based on WWW loggers attempt to track exposure to content through the identification of URL addresses (Uniform Resource Locator) used in the World Wide Web. The URL is basically an address that specifies the location of a file on a server connected to the Internet, and it specifies the exchange protocol to be used, port number, domain name, subdirectory names, file name, etc. In order to determine what content has actually been streamed or downloaded, each URL must be univocally linked to a specific content item identified in the web space. For this reason, tables associating media items available on the web space to URLs are required before any meaningful audience figures can be obtained. These tables need to be updated every time a change is introduced, which makes the process extremely burdensome and error-prone when the number of possible items becomes too large. Moreover, such relationship between URLs and content files is not guaranteed since some advanced programming methods do not use fixed URL addresses but dynamic ones that may not bear a direct correspondence to media files, which makes such a task unfeasible.
Furthermore, new programming techniques are becoming more popular among software developers that avoid the use of URLs (beyond the initial access to a portal page), which makes the linking between URL and media files unusable.
Moreover, current implementations of WWW logger measurement services cannot track time-shifted consumption, i.e., consumption of media that has been downloaded at one point in time, and consumed at a later point in time. In such cases, most WWW loggers cannot keep track of content that has been stored and consumed at a different time; such software applications can only track Internet browsing activity and other interactions with the World Wide Web in “real time”, i.e. “as it happens”.
In order to overcome such limitations, more functionality would be required from such software meters, so that they are able to track the activity of any type of media player, with the added capability of recognizing and reporting all content consumed through the use of the digital media terminal.
To complicate things further, even streamed content—as would be the case of on-demand video services—may not necessarily imply that the associated content is been viewed during the streaming session. A large variety of software applications are available that allow recording of audio and video streaming (also known as ‘stream rippers’). Content may be downloaded (i.e. recorded) through these methods and never played back, or played back only partially. Such methods based on logging WWW activity cannot detect and report accurately this type of media consumption.
Another limitation of WWW loggers is given by the increasing amount of peer-to-peer content sharing. Once the content is downloaded from an original server, the total number of users that access the data file is impossible to track. The only viable way to track audiences to such content files is though a ‘user centric’ (i.e., panel based) approach and using a content identification technique that reports any kind of exposure to such media.
Beyond the above discussed topic of the accuracy of ‘site-centric’ and ‘user centric’ methods for the audience measurement of on-line media consumption, time shifted viewing, and peer-to-peer content sharing, an issue that is highly relevant when using WWW loggers is privacy. In order to provide an accurate report of media consumption, WWW loggers need to track all browsing activity as well as use of other software applications, sometimes including keyboard activity. This becomes a privacy issue for many users.
A theoretical solution would be available to overcome many of the problems associated to measurement systems based on activity logs through the use of content identification techniques. Such theoretical solution would require the use of complex software techniques to intercept the audio or video stream being played back by the DMT in order to attempt identification of such content through some suitable method, such as detecting an embedded audio code or watermark, or comparing signatures or fingerprints of such streams.
However, such solution is not feasible since most operating systems running on digital media terminals do not provide any standard way of accessing digital audio streams being played back by the DMT for the purpose of copyright protection. For example, Microsoft® has implemented in its latest operating system Windows VistaTM a feature called “Protected Media Path” that makes it impossible to tap into any of the audio or video digital streams produced within the system, to protect that media content from any kind of tampering. Any method based on such principles cannot be implemented in standard operating systems, or cannot be guaranteed to work on every version and all possible configurations thereof.
Even if the playback digital stream would not be protected, such a solution would suffer from other problems that would make it impractical. For example, in the Windows XP environment it is possible to write a virtual audio driver software that can intercept any audio played back through any application running in that operating system, but only if the virtual audio driver is defined as the system's “default audio device”. Such a solution cannot ensure stable and uninterrupted operation, in all possible situations and all possible configurations, because it relies on software techniques that act at the lowest layers of the system. For example, such virtual drivers may interfere with preinstalled drivers or bear incompatibilities with other installed hardware devices, or may even change audio settings of the host digital media terminal every time it is invoked, hindering its normal use as a media player or as a communications device. That, in turn, significantly increases the risk of users refusing the installation of such software in their digital media terminals, or abandoning the panels for being excessively burdened by these inconveniences.
The aforementioned limitations of all known methods seriously limit the capabilities of any user-centric approach due to the impossibility of implementing a homogenous method across all possible distribution platforms and all types of DMTs. This drawback seriously compromises the representativeness and balance of statistical samples, which is a prerequisite of any audience measurement process.
SUMMARY
The invention is set out in the claims. A loop-back device derives a return signal from an outbound signal of a DMT. The return signal, carrying a sample signal derived from the outbound signal, is routed back to the same DMT through standard inbound audio facilities so that it can be captured by a conventional audio processing software application for content identification. The return signal may be derived by mixing the sample signal with an eventual inbound signal (for example, a conventional microphone used with the DMT for capturing human voice) producing thus a combined signal that contains the outbound signal and any eventual inbound signal. The mix so produced is then routed back into the DMT via a signal path connected to standard inbound audio facilities.
Because in most practical applications audio flows alternatively either outbound (i.e. from the DMT to the user, for example while consuming audiovisual media) or inbound (i.e. from the user to the DMT, for example while speaking into a microphone in a phone conversation), the return signal produced by the loop back device contains in most cases either the sample signal or the original inbound signal, in mutual exclusivity. This is true most of the time even in DMT applications involving the users (as for example in a phone conversation), since human beings tend to talk and listen at different times (i.e. not simultaneously). This natural propensity of users of employing outbound/inbound audio facilities alternatively while operating a DMT allows the utilization of those same standard audio facilities for audience measurement purposes, capturing samples of the media items consumed by those users without interfering in any significant way with the normal use of the DMT. Eventual interruptions observable in the sample signal given by sporadic activity in the inbound signal while capturing exposure to media do not affect the validity of the method as a statistical sampling mechanism for audience measurement purposes.
Because the invention uses standard outbound/inbound audio facilities that are included in the vast majority of digital media devices, conventional techniques can be used advantageously to capture the return signal, allowing capturing of most media exposure situations using substantially the same technique in various distribution platforms and types of DMTs. The loop-back device can be implemented by a relatively simple electronic circuit connected to a standard outbound audio facility of the monitored DMT. Such circuit produces an attenuated sample of the signal sent to an audio rendering device (used to reproduce such audio material, such as speakers connected to the DMT).
The present invention ensures that the media content to be monitored is captured “as rendered” to the user, using standard audio capturing software of the monitored DMT.
The present invention enables seamless and homogenous implementation of the method across different types of DMTs, hence enabling the construction and maintenance of balanced “user-centric” panels.
The present invention can be implemented advantageously at a marginal cost in those situations where a system is already in place for measuring audiences for other types of platforms (for example television), extending the capturing capabilities of such system to cover new digital distribution platforms while utilizing existing content identification facilities.
The present invention can be implemented without altering the media consumption habits of monitored users, beyond the extent to which the use of such loop-back device may do so.
The present invention can be implemented guaranteeing the privacy of users beyond the reporting of exposure to publicly available audio material, not relying on detailed logging of all browsing activity (even beyond media consumption purposes).
The present invention is particularly useful for monitoring media exposure through the use of headphones in a relatively simple and cost-effective way.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a digital media terminal used for media consumption.
FIG. 2 is a block diagram of a loop-back device according to the present invention.
FIG. 3 is a diagram showing dynamic levels of signals involved in operating the invention.
FIG. 4 is a diagram of a first embodiment of the invention.
FIG. 5 is a diagram of a second embodiment of the present invention, utilizing active circuits for improved performance.
FIG. 6 shows a diagram of a third embodiment of the present invention, also utilizing active circuits.
FIGS. 7A and 7B depict embodiments of the present invention, embodied in standard audio connectors.
FIG. 8 depicts yet another embodiment of the present invention, in this case embodied in standard headphones.
FIGS. 9A and 9B illustrate yet another embodiment of the present invention, in this case embodied in an accessory for a mobile-phone.
FIG. 10 is an illustration of yet another embodiment of the present invention, in this case embodied in a headphone using a digital audio interface (e.g. “USB audio”).
FIG. 11 is a block diagram of yet another embodiment of the present invention, in this case embodied in Bluetooth-enabled headphones.



DETAILED DESCRIPTION
FIG. 1 shows a block diagram of a typical digital media terminal 101 used for media consumption, including a central processing unit 102, an outbound audio facility 103, an inbound audio facility 106, a communications link 107, one or more broadcast signal receivers 108 and a memory 109.
Digital media terminal 101 may be, for example, a desktop personal computer (PC), a laptop PC, a handheld PC, a mobile communications device, a DVD player, a portable media player, a game console, a portable game console, a music player, a portable music player, or any other type of device including media playback and information storage capabilities.
Outbound audio facility 103 may be any combination of hardware and/or software elements capable of producing an outbound signal 104 driving an audio rendering device 110. Examples of audio rendering devices include a speaker, a headset, an earphone, etc. The inbound audio facility 106 may be any combination of hardware and/or software elements capable of capturing an inbound signal 105, allowing connection of an audio sensing device 111 to digital media terminal 101 (such as a microphone or some other kind of external audio source).
Digital media terminal 101 may be equipped as well with communication capabilities (represented in FIG. 1 by “Comms link 107”) which may include any combination of hardware and software elements allowing a data connection (e.g., WiFi, Ethernet, ADSL, GPRS, UMTS, CDMA, WiMax, etc.). Digital media terminal 101 may be also equipped with broadcast signal receiver 108, which may include for example: a digital terrestrial television decoder, a mobile television receiver, a satellite television receiver, or any combination of hardware and software elements capable of receiving media through a broadcast signal. Memory 109 may include any type of computer data storage means, both volatile and non-volatile.
Content identification technologies may be implemented in a digital media terminal by means of a software application running on the same device being monitored for media measurement purposes. Known content identification technologies may include: methods based on matching audio signatures or fingerprints, on extraction of embedded audio codes, detection of specific content features, etc. Such software application must be capable of processing a given digital signal stream obtained from a standard audio facility of digital media terminal 101, according to what is prescribed for the content identification technology used (for example, generating a signature or extracting an ID code or fingerprint). Such software application may realize also the functions of storing that information in a memory resource of digital media terminal 101, and further transmitting the information to a central processing base, whenever a communication link with such base becomes available (e.g. an Internet connection).
FIG. 2 shows a block diagram of a loop-back device 124 according to the present invention. In most embodiments, loop-back device 124 is inserted in the outbound and inbound signal paths between digital media terminal 101 and audio rendering device 110 and audio sensing device 111, coupled to outbound signal 104 and inbound signal 105. Loop-back device 124 is connected to outbound audio facility 103 and to inbound audio facility 106 by means of any standard or proprietary interfaces or connectors, and includes a sampling circuit 136 for producing a sample signal 125 and a mixer circuit 137 for producing a return signal 126.
Sample signal 125 is an attenuated version of outbound signal 104 which is routed back into digital media terminal 101 as a component of return signal 126 through mixer circuit 137, in order to enable a content identification process within digital media terminal 101 for audience measurement purposes. Mixer circuit 137 allows inbound signal 105 (if present) to be routed as well to digital media terminal 101 as another component of return signal 126, in order to enable the usual purpose for which audio sensing device 111 is used (e.g. a mobile telephone's microphone included in a headset). Return signal 126 configures hence a mix of inbound signal 105 and sample signal 125, and is routed back into digital media terminal 101 via a signal path connected to standard inbound audio facility 106 (e.g. a wire or connector), in replacement of original inbound signal 105.
In those cases in which inbound signal 105 exists (according to the application of digital media terminal 101), return signal 126 produced by loop back device 124 contains—most of the time—either sample signal 125 or inbound signal 105, in mutual exclusivity, due to the users' natural tendency of receiving or generating audio at different, alternate times. It will be apparent to those skilled in the art that, in some applications of the invention, inbound signal 105 may not be present all the time, or may not be present at all. For example, the invention may be applied to capturing exposure to media in a desktop PC computer setup in which no microphone is installed nor used (e.g. a Windows Media Center PC used only for rendering media but not for personal intercommunication applications). In such case inbound signal 105 is inactive all (or most) of the time; however the invention still solves the problem of capturing a sample of outbound signal 104 and routing it back to the digital media terminal for audience measurement purposes, via standard audio resources available in most DMT devices, without substantially modifying the way such devices are used according to its original intended purposes.
The audio material to be identified is hence contained in return signal 126 and made available at standard inbound streams within digital media terminal 101, so that it can be read by capturing software 134 by reading inbound streams within an operating environment running in digital media terminal 101. Such task may be accomplished by standard routines as those used for recording audio in media terminal 101, being its compatibility assured by being basic operating services available in all types of DMTs. Capturing software 134 may record return signal 126 and store it in memory 109 for later retrieval, or may produce signatures from return signal 126 for later identification through correlation techniques, or may as well process return signal 126 “on the fly” to detect embedded or watermarking codes previously inserted in the broadcast path for content identification, storing in this case the detected codes in memory 109 for later retrieval, or use a combination of known content identification methods. In most operating environments, capturing software 134 may continuously read streams produced by inbound audio facility 106 independently and concurrently with any other software applications running in media terminal 101 that require its use for other purposes (e.g. a voice recording software application running in background mode within digital media terminal 101).
Sampling circuit 136 produces a sample signal 125 attenuated enough to minimize any undesirable feedback to a remote subject in inter-communication applications (e.g. mobile phone applications), but still producing a signal strong enough to be detected by the chosen content identification method.
FIG. 4 shows a diagram of a first embodiment of the invention including a passive electronic mesh comprising condenser C1 and resistors R1 and R2. As shown in FIG. 4, sampling circuit 136 is configured by condenser C1 and resistor R1 connected between output wire 141 carrying outbound signal 104 and input wire 142 carrying return signal 126. Resistor R2 connects the wire carrying inbound signal 105 (if available) to mixer circuit 137, which is implemented by means of a simple current summing node 171, where the signals contributed by resistors R1 and R2 are added to produce return signal 126. Return signal 126 is routed to digital media terminal 101 through standard inbound audio facility 106.
The value of all electronic components must be defined in order to produce a compromise between the following requirements:
Condition (1): the strength of sample signal 125 within return signal 126 must be strong enough to allow effective content identification by the method in use; and,
Condition (2): the strength of sample signal 125 within return signal 126 must be low enough as to avoid oscillations or significant echo effects when digital media terminal 101 is used for applications other than consuming media (for example, mobile phone or other intercommunication applications).
The satisfaction of condition (1) depends mostly on the noise floor produced by the inevitable background audio captured by audio sensing device 111 (if present). In most practical applications of the invention, audio sensing device 111 happens to be designed to capture sound waves typically from a few centimeters away from the user's mouth (e.g. a microphone incorporated in a headset or earphone). Such sound level produced by audio sensing device 111 in normal operating conditions (e.g. when a user is speaking into a microphone) will be referred to as “normal inbound level”, while the sound level produced by background noise sources in the same operating conditions will be referred to as “normal background noise level”. It can be observed that in most practical cases the normal background noise level falls typically at 25-30 decibels below normal inbound level, as shown in FIG. 3. This is explained by the power and intensity loss suffered by sound waves as they are propagated over the air, and by the fact that users would usually not be able or would not choose to consume media in situations where they cannot hear the desired audio material with enough clarity, respect to the background noise. This creates room within the dynamic range of return signal 126 to insert sample signal 125 (or a derivative thereof) at a power level high enough to enable a content identification process, but still low enough to prevent disturbing a user of digital media terminal 101 when audio facility 106 is required for other purposes (e.g. phone communications).
Using FIG. 3 as a guideline, if the value of components is set such that sample signal 125 enters mixing circuit 137 (i.e. node 171) at, for example, 20 decibels below the normal inbound level (see FIG. 3), in most practical cases it ends up at about 10 decibels above the normal background noise level, which is enough to enable content identification (assuming the use of appropriate content identification methods).
Regarding condition (2), it can be observed that in the vast majority of applications regarding media consumption inbound audio facility 106 remains idle for any period of time devoted to media consumption. As explained in the summary section, this is because of the natural propensity of users of employing outbound/inbound audio facilities alternatively while operating a DMT, and because most operating environments do not preclude the use of inbound audio facilities while outbound audio facilities are in use by some other application. On the other hand, when/if digital media terminal 101 is used for voice inter-communications, it has been observed that most digital intercommunication systems and services, whether based on circuit-switching or data networks of any kind, typically provide quite effective echo cancellation services, usually effective enough to eliminate (or at least substantially reduce) any undesired echo effect.
It will be apparent to those skilled in the art that a large number of alternative circuits may be used to obtain a comparable result. The above implementation is provided herein as an exemplary circuit that is able to provide satisfactory results in most operating conditions, having at the same time the advantage of minimum part count, minimum manufacturing costs and minimum operating costs.
Alternative embodiments of loop-back device 124 are also possible that utilize active components to further improve its performance in highly-noisy environments, as shown in FIGS. 5 and 6. For example, a variable attenuator may be used in place of resistor R2 to achieve a more dynamic control of the amount of inbound signal 105 mixed with sample signal 125, according to a sound level indication detected in the same inbound signal 105 produced by audio sensing device 111. As shown in FIG. 5, such embodiment of loop-back device 124 includes noise gate 190 that monitors the signal level at inbound signal 105 and allows it to flow forward into node 171 only when it complies with predefined conditions (e.g. exceeds a predefined threshold). Such functionality enables inbound signal 105 only at those times at which a user is perceived as wishing to talk (i.e. relatively high sound power detected at sensing device 111), preventing background noise from staining return signal 126 at every other time. It will be apparent to those skilled in the art that more sophisticated transfer functions for noise gate 190 can be defined to optimize the overall result in most conditions. For example, attack and release times of noise gate 190 may be adjusted to reduce any undesirable effects while using digital media terminal 101 for conversation. In this sense, a short attack time is recommended so that the user does not feel any impediment for communicating, while a relatively long release time may be helpful in providing a more natural feel to the counterparty during a conversation. Again, it is observed that audio content consumers usually do not speak while they are hearing, except for certain specific activities such as, for example, karaoke singing or studio recording applications, in which case the use of loop-back device 101 would neither be recommended nor necessary.
FIG. 6 shows yet another embodiment of loop-back device 124 using active circuits including as well a variable attenuator on the signal path of inbound signal 105, although in this case the level indication is derived from outbound signal 104. For this purpose, a level detector circuit 198 is included that activates a signal attenuator 197 when a certain level of activity is detected in outbound signal 104 (e.g. when the power level indication exceeds a predefined threshold). Being observed that human beings cannot hear and speak at the same time during any application requiring speaking and hearing (e.g., a conversation) attenuating inbound signal 105 while outbound signal 104 is active (i.e. media is flowing out of the DMT or the remote end may be speaking) does not have a perceivable effect from the user's point of view, still enhancing the performance of loop-back device 124 by further protecting the “integrity” of return signal 126 from ambient noise captured by audio sensing device 111 during media consumption sessions. The embodiments depicted in FIGS. 5 and 6 can also be combined in a single embodiment to provide a more elaborate control of the amount of inbound signal 105 introduced in return signal 126. Further possible enhancements will be apparent regarding the derivation of sample signal 125, which may include additional active elements for modifying sample signal 125 in terms of equalization, dynamics (e.g. compression) or any other processing that may be required to optimize return signal 126, according to what is prescribed by the chosen content identification method.
FIGS. 7A and 7B depict an example of realization of the present invention aimed to monitoring media consumption through the use of desktop personal computers or similar digital terminals. FIG. 7A shows standard 3.5 mm audio input and output connectors of digital media terminal 101, including a microphone connector 151, a stereo audio output connector 152 and a stereo line-in connector 153. Loop-back device 124 (not shown in the picture) is embodied in an apparatus 160 housing standard 3.5 mm plugs that are inserted in standard microphone connector 151 and to the stereo audio output connector 152. A visible mark is included in apparatus 160 to easily remind the user about which one of the connectors should be inserted in the standard output jack of the DMT. Apparatus 160 further includes two 3.5 mm jacks 154 and 155 which allow for the connection of an external audio sensing device (if any) and an external audio rendering device 110 (e.g., a pair of headphones or a set of speakers). FIG. 7B shows apparatus 160 connected in an alternative way in which the loop-back circuit is implemented between stereo audio output connector 152 and stereo line-in connector 153, and connectors 154 and 155 allow for the connection of an external audio rendering device 110 (e.g., a pair of headphones, or a set of speakers) and an external audio source.
FIG. 8 depicts another example of realization of the invention where apparatus 160 is implemented as part of a personal media-rendering device, in FIG. 8 exemplified as headphone 181. This particular embodiment is convenient for applying the invention in the measurement of media consumption through the use of laptop PCs and some types of hand-held devices (for example “smart” mobile phones). Headphone 181 of the invention may be easily derived from an existing headphone device by inserting loop-back device 124 in the headphone cable 180, through a relatively simple manufacturing process applied on off-the-shelf commercial units. In this way, headphone 181 is connected to digital media terminal 101 through its own original connectors 176. Headphones of the kind of headphone 181 may be gifted to individuals participating in audience measurement panels as an extra incentive to cooperate in the measurement process, ensuring that return signal 126 is always available while users are exposed to media through that consumption mode. Any of the alternatives described herein for realization of loop-back device 124 can be used in this particular embodiment.
FIG. 9A depicts yet another embodiment of the present invention wherein apparatus 160 of FIGS. 7A, 7B and 8 is embodied in apparatus 190 taking the shape of a single plug-jack combination device, as shown in FIG. 9A. Any of the alternatives described herein for realization of loop-back device 124 can be used in this particular embodiment. Apparatus 190 includes a jack connector 191 which allows for connecting a plug similar to the one included in the same apparatus, allowing realizing the invention using standard (i.e. unmodified) headphones or headsets. A standard 3.5 mm jack type of connector is shown as an example in FIGS. 9A and 9B, although it should be apparent that apparatus 190 can be implemented with many other types of connectors, both standard and proprietary. This particular embodiment is convenient when the invention is applied to monitor media usage in a mobile communication device (192 in FIG. 9B with and its associated headset 193).
FIG. 10 depicts yet another embodiment of the present invention in association with a “USB headset”. Many headsets are offered today in the markets that are not connected to a DMT through simple analogue audio connectors, but through a digital link, for example a USB port. Such headphones include a complete “audio card” circuit inside the USB connector or the headset's cable where all the A/D and D/A conversion takes place, while all communication with the host DMT happens in digital form.
FIG. 10 depicts such embodiment, where a USB connector 216 is used as a communication port with the DMT. As show in FIG. 10, in this case the loop-back device 124 can be conveniently implemented after the D/A conversion stage 212 acting in the analogue domain as described in the various examples herein. This embodiment is convenient in those cases in which a panel member has already a USB headphone and wishes to continue to use a similar technology for his/her media consumption activities.
The present invention can be successfully realized even in a wireless personal rendering device. Wireless headsets have become very popular thanks to the advent of low-cost wireless technologies like Bluetooth. A wireless headset comprises a remote unit including one or two small speakers and optionally a microphone (if it is intended for use in personal telecommunications). In such cases, loop-back device 124 can be advantageously housed in the remote unit in proximity of the speakers (audio rendering devices) and microphone (audio sensing device, if available). Such embodiment of the invention is shown in FIG. 11, implemented in an exemplary Bluetooth® headset 200, shown in the figure as composed of: antenna 201, radio-frequency stage 202, Bluetooth® circuitry 204, audio codec 205, signal amplifier 206, earphones 207 and a microphone 208. Return signal 126 thus generated is automatically processed and transmitted by the above mentioned elements of headset 200 to an associated digital media terminal 101 (not shown in the picture).
The present invention can be advantageously applied in a variety of audience measurement processes that make use of audio content identification technologies, including broadcasted radio and television audiences as well as audiences to downloaded and/or streamed music and/or video, or any other applications where a digital media terminal is used as a media rendering device.
Finally, although certain example methods, apparatus and articles of manufacture have been described 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 appended claims either literally or under the doctrine of equivalents.

## Claims

1. A system for measuring exposure of a user to media, the system comprising:
a digital media terminal to present the media, the digital media terminal being equipped with at least an outbound audio facility and an inbound audio facility;
an electronic circuit coupled to the outbound audio facility and the inbound audio facility, the electronic circuit comprising:
loop-back circuitry to add an inbound signal receivable by the digital media terminal with an outbound signal generated by the outbound audio facility to generate a return signal, and to route the return signal back to the digital media terminal via a signal path connecting to the inbound audio facility;
a level detector responsive to a level of the outbound signal; and
an attenuator to adjust a level of the inbound signal before the inbound signal is added with the outbound signal to generate the return signal, the attenuator being controllable according to an output of the level detector; and

media identification software running in the digital media terminal, the media identification software programmed to process the return signal and to derive media identification information therefrom.

2. A system according to claim 1 wherein the loop-back circuitry includes mixing circuitry to add a sample of the outbound signal with a sample of the inbound signal to produce the return signal.

3. A system according to claim 1 wherein the attenuator is located in a signal path of the inbound signal.

4. A system according to claim 1 wherein the level detector is in communication with the outbound audio facility.

5. A system according to claim 1 wherein the loop-back circuitry further includes a noise gate responsive to the inbound signal, the noise gate to block the inbound signal from being added with the outbound signal based on a level of the inbound signal.

6. A method for measuring exposure of a user to media rendered by a digital media terminal, the method comprising:
deriving a return signal from an outbound signal generated by the digital media terminal, the return signal being derived by:
adjusting a level of an inbound signal received by the digital media terminal, the level of the inbound signal being adjusted according to a first level indication derived from a level of the outbound signal; and
adding the inbound signal, after being adjusted, with the outbound signal to derive the return signal;

routing the return signal into the digital media terminal via a signal path connecting to an inbound audio facility of the digital media terminal;
processing the return signal using a software application running in the digital media terminal; and
deriving media identification information from the processing of the return signal using the software application.

7. A method according to claim 6 wherein deriving the return signal comprises adding a sample of the inbound signal with a sample of the outbound signal.

8. A method according to claim 7 wherein the sample of the outbound signal is added with the sample of the inbound signal only if an acoustic property of the inbound signal exceeds a threshold.

9. A method according to claim 6 wherein the first level indication comprises an amplitude level indication derived from the outbound signal.

10. A method according to claim 6 wherein an acoustic level of the outbound signal is controlled during the adding to distinguish the outbound signal from a desired inbound signal to be received by the digital media terminal.

11. A method according to claim 10 wherein the acoustic level of the outbound signal is controlled to be between 5 and 25 decibels (dB) below an acoustic level of the desired inbound signal during the adding.

12. A method according to claim 6 further comprising blocking the inbound signal from being added with the outbound signal based on an amplitude level indication derived from the inbound signal.

13. A device to measure exposure of a user to media rendered by a digital media terminal, the device including an electronic circuit arranged to be coupled to an outbound audio facility and an inbound audio facility of the digital media terminal, the electronic circuit including:
loop-back circuitry to add an inbound signal receivable by the digital media terminal with an outbound signal produced by the digital media terminal to produce a return signal, the loop-back circuitry to route the return signal to the digital media terminal via a signal path in communication with the inbound audio facility for content identification purposes;
a level detector responsive to a level of the outbound signal; and
an attenuator to adjust a level of the inbound signal before the inbound signal is added with the outbound signal to produce the return signal, the attenuator being controllable according to an output of the level detector.

14. A device according to claim 13 wherein the loop-back circuitry includes mixing circuitry to add a sample of the outbound signal with a sample of the inbound signal to produce the return signal.

15. A device according to claim 13 wherein the attenuator is located in a signal path of the inbound signal.

16. A device according to claim 13 wherein the attenuator is controllable according to a level indication provided by the level detector.

17. A device according to claim 13 wherein the electronic circuit further includes a noise gate responsive to the inbound signal, the noise gate to block the inbound signal from being added with the outbound signal based on a level of the inbound signal.

18. A device according to claim 13 wherein the electronic circuit is included in a personal rendering device comprising at least one of an audio rendering device or an audio sensing device.

19. A device according to claim 18 wherein the personal rendering device includes a cable arranged to transmit the outbound signal and the inbound signal, and the electronic circuit is included in a housing physically connected to the cable.

20. A device according to claim 18 wherein the personal rendering device is arranged to be coupled to the digital media terminal through a digital link and the loop-back circuitry is arranged to be coupled to respective analog stages of the outbound audio facility and the inbound audio facility.

21. A device according to claim 20 wherein the digital link is implemented by a radio link communicatively coupling the digital media terminal with a remote unit housing the personal rendering device.