Method and apparatus for identifying a digital audio dignal

A signal identification process which receives an input digital audio signal, the process comprising:

• performing at least one of:
• i) determining an identification code from a portion of a compressed received input digital audio signal, and extracting a signature from a portion of said compressed received input digital audio signal;
• and
• ii) determining an identification code from a portion of an uncompressed received input digital audio signal, and extracting a signature from a portion of said uncompressed received input digital audio signal.

A computer readable storage medium which causes one or more computers to carry out a signal identification process which receives an input digital audio signal, the computer readable storage medium causing the one or more computers to

• at least one of:
• i) determine an identification code from a portion of a compressed received input digital audio signal, and extract a signature from a portion of said compressed received input digital audio signal;
• and
• ii) determine an identification code from a portion of an uncompressed input digital audio signal, and extract a signature from a portion of said uncompressed received input digital audio signal.

A measurement apparatus for determining which of a plurality of digitally broadcast program signals is tuned by a broadcast receiver apparatus having a receiver output connector for outputting a digital audio signal, the measurement apparatus comprising:

• an input connector configured to connect the measurement apparatus to the receiver output connector;
• a repeater circuit configured to receive the digital audio signal and to supply a repeated copy thereof to an output connector portion of the measurement apparatus;
• a clock configured to supply a read time output;
• a decoding circuit having an input from the clock, the decoding circuit configured to read an ancillary code from the digital audio signal to associate a read time therewith;
• a signature extractor having an input from the clock, the signature extractor configured to extract a digital signature from the digital audio signal and to associate the read time therewith;
• a memory configured to store a plurality of data records, each of the data records comprising a respective read time and at least one of the ancillary code associated therewith and the digital signature associated therewith;
• and
• a communication device configured to communicate the plurality of data records to a data collection facility.

A method for generating a time-stamped tuning record for determining which one of a plurality of program signals is selected at a receiving site by a receiver apparatus having a receiver output connector configured to output a digital audio signal uniquely associated with the selected one of the program signals, the digital audio signal comprising a sequence of frames, the method comprising:

• receiving the digital audio signal from the receiver output connector;
• supplying a repeated copy of the digital audio signal to an output connector other than the receiver output connector;
• attempting to read, from a predetermined field of one of the frames, a respective first ancillary code from the digital audio signal;
• copying a predetermined portion of one of the frames as a respective first digital signature;
• assembling the time-stamped tuning record from a read time datum representing a time at which the one of the frames was received from the receiver output connector and at least one of the first ancillary code and the first digital signature;
• and
• communicating the time-stamped record to a data collection facility.

A method for generating a time-stamped tuning record for determining which one of a plurality of program signals is selected at a receiving site at a read time by a receiver apparatus having a receiver output connector configured to output a digital audio signal, the digital audio signal uniquely associated with the selected one of the program signals, the method comprising:

• receiving the digital audio signal from the receiver output connector;
• attempting to read an ancillary code embedded in the digital audio signal;
• extracting a digital signature from the digital audio signal;
• assembling the time-stamped tuning record from the read time and at least one of the ancillary code and first digital signature;
• and
• communicating the time-stamped record to a data collection facility.

A measurement apparatus for determining which of a plurality of program signals is selected by a receiver apparatus having an SP/DIF output connector for outputting a receiver output digital audio signal uniquely associated with the selected program signal, the receiver output digital audio signal having one of a non-linear PCM encoded audio bitstream signal format and a linear PCM audio signal format, the measurement apparatus comprising:

• an input connector configured to connect the measurement apparatus to the SP/DIF output connector;
• a clock configured to supply a read time output;
• a first decoding circuit configured to receiver the read time output, the first decoding circuit configured to read an ancillary code from the digital audio signal if the digital audio signal has the non-linear PCM encoded audio bitstream format and to associate a read time therewith;
• a first signature extractor configured to receive the read time output, the first signature extractor configured to extract a first digital signature from the digital audio signal if the digital audio signal has the non-linear PCM encoded audio bitstream format and to associate the read time therewith;
• a signal decompression circuit configured to convert the receiver output digital audio signal to a converted linear PCM audio signal if the digital audio signal has the non-linear PCM encoded audio bitstream format;
• a second decoding circuit configured to receive the read time output, the second decoding circuit configured to read an embedded code from one of the receiver output PCM digital audio signal and the converted linear PCM audio signal and to associate the read time therewith;
• a second signature extractor configured to receiver the read time output, the second signature extractor configured to extract a second digital signature from one of the receiver output PCM digital audio signal and the converted PCM digital audio signal, and to associate the read time therewith;
• a memory configured to store a plurality of data records, each of the data records comprising a respective read time and at least one of the respective first ancillary code, the respective first digital signature, the respective embedded code and the respective second digital signature associated therewith;
• and
• communication means configured to communicate the plurality of data records to a data collection facility.

A method for generating a time-stamped tuning record for determining which of a plurality of program signals is selected at a receiving site by a receiver having a receiver output connector configured to output a receiver output digital audio signal in either a linear PCM format or a non-linear PCM encoded audio bitstream format, the receiver output digital audio signal uniquely associated with a selected one of the program signals, the method comprising:

• receiving the receiver output digital audio signal from the receiver output connector;
• determining if the receiver output digital audio signal is the non-linear PCM encoded audio bitsream signal or the linear PCM signal;
• if the receiver output digital signal is the non-linear PCM encoded audio bitstream signal, attempting to read, from a predetermined field of each frame, a first ancillary code from the receiver output digital signal;
• if the receiver output digital signal is a non-linear PCM encoded audio bitstream signal, copying a predetermined portion of each frame as a first digital signature;
• if the receiver output digital signal is a non-linear PCM encoded audio bitstream signal, decompressing the non-linear PCM encoded audio bistream signal to yield a decompressed PCM digital signal;
• attempting to read, from one of the receiver output PCM digital signal and the decompressed PCM digital signal, a second ancillary code embedded therein;
• extracting a second digital signature from one of the receiver output PCM digital signal and the decompressed PCM digital signal;
• assembling the time-stamped tuning record from a read time datum and at least one of the first ancillary code, the first digital signature, the second ancillary code and the second digital signature;
• and
• communicating the time-stamped record to a data collection facility.

A broadcast audience measurement method for determining which one of a predetermined number of broadcast signals is tuned by a receiving apparatus at a statistically selected tuning site at a plurality of tuning times, wherein each of the broadcast signals comprises a respective digital audio component formatted as a respective sequence of data frames, and wherein the receiving apparatus comprises an output connector supplying the digital audio signal, the method comprising:

• selecting a subset of the data frames from the tuned broadcast signal;
• associating a respective tuning time with each of the data frames in the subset;
• storing a set of tuning records in a tuning memory at the tuning site, each of the tuning records comprising a copy of a predetermined portion of a respective data frame in the subset and the respective tuning time;
• communicating the set of tuning records to a central data collection facility;
• receiving the predetermined number of broadcast signals at at least one reference site, and storing a respective set of time-stamped reference records in a reference memory, each of the sets of reference records comprising a copy of the predetermined portion of each of the data frames of the digital audio component associated with a respective one of the broadcast signals;
• communicating the sets of reference records to the central data collection facility;
• and
• comparing, at the central data collection facility, the set of tuning records with ones of the sets of reference records to determine which of the broadcast signals is the tuned broadcast signal.