Television ratings information is typically generated by collecting viewing records or other viewing information from a group of statistically selected households. Each of the statistically selected households typically has a data logging and processing unit commonly referred to as a “home unit.” The home unit is often in communication with a variety of attachments that provide inputs to the home unit or receive outputs from the home unit. The home unit usually processes the inputs (e.g., channel tuning information, viewer identification information, etc.) from the attachments to produce viewing records. Viewing records may be generated on a periodic basis (i.e., at fixed time intervals) or may be generated in response to a change in an input such as, for example, a change in the identities of the persons viewing the television, a change in the channel tuning information (i.e., a channel change), etc. In any case, each viewing record typically contains channel information such as a station or channel number and a time (e.g., a date and time of day) at which the channel was viewed. Of course, viewing records may contain other information such as the identities of viewers present at the viewing time.
Often, the home unit collects a quantity of viewing records and transmits collected viewing records, usually daily, to a central data processing facility for further processing or analysis. The central data processing facility receives viewing records from home units located in some or all of the statistically selected households and analyzes the viewing records to ascertain the viewing behaviors of a particular household or a particular group of households selected from all participating households. Additionally, the central data processing facility may generate viewing behavior statistics and other parameters indicative of viewing behavior associated with some or all of the participating households.
To generate viewing behavior information from viewing records, the central data processing facility compares reference data such as a list of programs (i.e., a schedule of television programming or lineup) to the viewing records. In this manner, the central data processing facility can determine which program was viewed by matching the time and channel information in a viewing record to the program associated with that same time and channel in the program schedule or lineup. Such a matching process can be carried out for each of the viewing records received by the central data processing facility, thereby enabling the central data processing facility to reconstruct what programs were watched or consumed by all participating households and the times at which the programs were consumed.
While known methods and apparatus for ascertaining the viewing behavior of a large population are well suited for viewing records associated with live viewing of television programming, these techniques are not suitable for use with audio and/or video programs that are recorded and viewed later. In particular, for pre-recorded program information, the viewing time is delayed with respect to the time at which the program information was available as a live program. As a result, viewing records containing viewing time information cannot be compared to reference program guide information at the central data processing facility to determine what programs are associated with the viewing records. Further, the tuning information available from, for example, a frequency detector attachment in communication with a television that is being used to display a previously recorded program does not provide useful tuning information. More specifically, the recorded program is typically supplied by a video recording device (e.g., a VCR) or the like that sends unmodulated low-level audio and video signals to the audio and video inputs of the television that bypass the tuner circuitry of the television.
The use of digital video recording devices (DVR's), personal video recording devices (PVR's) such as the TiVo® system further complicates collection of viewing behavior information because viewers in households with these types of recording devices can rapidly change between live viewing of a program, time-delayed viewing of the program, fast forwarding and rewinding the program, pausing the program, and/or recording the program for later viewing. The use of processing techniques based on recognition of program signatures has been employed in some cases where it is difficult to obtain accurate timing information and in cases where it may otherwise be difficult to obtain viewing time information and channel information associated with the currently viewed program content. However, these processing techniques are not well suited for use in situations where a recording device may enable rapid changes between live viewing of a program, delayed viewing of the program, viewing of another program while recording the program, etc.
Further, digital television (DTV) systems are expected to supplant traditional analog television systems in the near future because DTV systems offer interactivity to viewers, and provide compatibility with computers and/or the Internet and better image resolution and audio quality than traditional analog television systems. In particular, DTV systems broadcast programs by modulating one or more streams of digital packets on a single carrier frequency (e.g., a major channel). Because multiple streams of data packets can be multiplexed on a single carrier frequency, multiple programs can be carried by that single frequency (e.g., one or more minor channels). Although the technology used to broadcast and receive television signals is changing, the need to monitor the size and demographic composition of the viewing audience is not changing. To identify viewing information, for example, existing methods and apparatus identify the major channel by identifying the frequency tuned by the tuner of a DTV and/or a set top box (STB). However, unless the major channel carries only one minor channel, the identification of the major channel does not identify which of the minor channels are being tuned (e.g., which of the multiple programs are consumed by viewers). Faced with changing technology, audience measurement companies are developing new ways to efficiently and accurately gather the desired viewing information from DTV's and/or STB's.