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EP-4738848-A1 - UPDATING A WATERMARK ACCUMULATION BUFFER TO AVOID FALSE DETECTIONS

EP4738848A1EP 4738848 A1EP4738848 A1EP 4738848A1EP-4738848-A1

Abstract

An example method includes decoding a portion of audio so as to determine, for respective symbol slots of a watermark, current strength values for respective symbols. The method also includes determining, for the respective symbol slots, expected symbols of an expected message. In addition, the method includes determining a current score for the portion of audio using current strength values for the expected symbols and averages of current strength values for unexpected symbols. The method also includes determining an accumulation score for the portion of audio using accumulated strength values for the expected symbols and averages of accumulated strength values for the unexpected symbols. And the method includes, based on a detected divergence between the current score and the accumulation score, reinitializing the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols.

Inventors

  • KUZNETSOV, VLADIMIR
  • GISH, DAVID

Assignees

  • The Nielsen Company (US), LLC

Dates

Publication Date
20260506
Application Date
20251008

Claims (15)

  1. A computing system comprising a processor and a memory, the computing system configured to perform a set of acts comprising: decoding a portion of audio so as to determine, for respective symbol slots of a watermark, current strength values for respective symbols; determining, for the respective symbol slots, expected symbols of an expected message; determining a current score for the portion of audio using current strength values for the expected symbols and averages of current strength values for unexpected symbols; determining an accumulation score for the portion of audio using accumulated strength values for the expected symbols and averages of accumulated strength values for the unexpected symbols; and based on a detected divergence between the current score and the accumulation score, reinitializing the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols.
  2. The computing system of claim 1, wherein determining the current score comprises: for each of two or more of the respective symbol slots: determining a current symbol score using i) the current strength value for the expected symbol value for the respective symbol slot and ii) an average of the current strength values for the unexpected symbols for the respective symbol slot; and combining the current symbol scores for the two or more respective symbol slots.
  3. The computing system of claim 1 or claim 2, wherein determining the accumulation score comprises: for each of two or more of the respective symbol slots: determining an accumulation symbol score using i) the accumulated strength value for the expected symbol value for the respective symbol slot and ii) an average of the accumulated strength values for the unexpected symbols for the respective symbol slot; and combining the accumulation symbol scores for the two or more respective symbol slots.
  4. The computing system of any preceding claim, wherein the set of acts further comprises adding the current strength values for the respective symbols to values stored in a buffer so as to obtain the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols.
  5. The computing system of any preceding claim, wherein the expected message is a message that: was previously decoded within a threshold time of a time of the decoding of the portion of the audio, and was verified as a valid message.
  6. The computing system of any preceding claim, wherein the set of acts further comprises detecting the divergence by determining that a difference between the accumulation score and the current score satisfies a threshold condition.
  7. The computing system of any preceding claim, wherein reinitializing the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols comprises reinitializing the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols with the current strength values for the respective symbols.
  8. The computing system of any preceding claim, wherein: the set of acts further comprises obtaining the portion of audio using a microphone; and/or the computing system is a component of an audience measurement meter.
  9. A method comprising: decoding, by a computing system, a portion of audio so as to determine, for respective symbol slots of a watermark, current strength values for respective symbols; determining, by the computing system for the respective symbol slots, expected symbols of an expected message; determining, by the computing system, a current score for the portion of audio using current strength values for the expected symbols and averages of current strength values for unexpected symbols; determining, by the computing system, an accumulation score for the portion of audio using accumulated strength values for the expected symbols and averages of accumulated strength values for the unexpected symbols; and based on a detected divergence between the current score and the accumulation score, reinitializing, by the computing system, the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols.
  10. The method of claim 9, wherein: determining the current score comprises a) for each of two or more of the respective symbol slots: determining a current symbol score using i) the current strength value for the expected symbol value for the respective symbol slot and ii) an average of the current strength values for the unexpected symbols for the respective symbol slot, and b) combining the current symbol scores for the two or more respective symbol slots; and/or determining the accumulation score comprises a) for each of two or more of the respective symbol slots: determining an accumulation symbol score using i) the accumulated strength value for the expected symbol value for the respective symbol slot and ii) an average of the accumulated strength values for the unexpected symbols for the respective symbol slot, and b) combining the accumulation symbol scores for the two or more respective symbol slots.
  11. The method of claim 9 or claim 10, further comprising: adding the current strength values for the respective symbols to values stored in a buffer so as to obtain the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols; and/or detecting the divergence by determining that a difference between the accumulation score and the current score satisfies a threshold condition.
  12. The method of any one of claims 9 to 11, wherein the expected message is a message that: was previously decoded within a threshold time of a time of the decoding of the portion of the audio, and was verified as a valid message.
  13. The method of any one of claim 9 to 12, wherein reinitializing the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols comprises reinitializing the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols with the current strength values for the respective symbols.
  14. The method of any one of claims 9 to 13, further comprising obtaining the portion of audio using a microphone.
  15. A non-transitory computer-readable medium having stored therein instructions that, when executed by a computing system, cause the computing system to perform the method of any one of claims 9 to 14.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63/715,979, filed on November 4, 2024, and of U.S. Patent Application No. 19/333,622, filed on September 19, 2025, the entire contents of which are hereby incorporated by reference. BACKGROUND Watermarking can be used to insert additional information into media. For example, watermark encoders sometimes embed audio watermarks in audio signals to convey media identification information. By detecting watermarks present in television broadcasts, radio broadcasts, and/or streamed multimedia, an audience measurement entity (AME) can monitor the distribution and/or use of media. An accumulation buffer is a technique that allows an audio watermark to be decoded despite high levels of acoustic noise. As a simplified example, to detect a symbol of a first watermark message, a watermark decoder may measure watermark symbol values corresponding to each possible symbol value the symbol may have. Further, the watermark decoder may store the measured watermark symbol values in a buffer. When detecting the same symbol of a second watermark message, the watermark decoder may again measure watermark symbol values for the possible symbol values, and combine the measured watermark symbol values with the previously measured watermark symbol values stored in the buffer. The watermark decoder can then decode the symbol for the second watermark message using the accumulated watermark symbol values, as opposed to decoding the symbol for the second watermark message using solely the measured watermark symbol values for the second message. SUMMARY Disclosed herein are systems and methods for decoding watermarks in a manner that reduces false watermark detections that may occur due to the use of an accumulation buffer technique. Within examples, a watermark decoder reinitializes values stored in a buffer based on detecting a divergence between measured strength values of a current watermark message and strength values accumulated over multiple watermark messages. This allows the watermark decoder to more quickly detect changes in watermarked media. In one aspect, a computing system is described. The computing system includes a processor and a memory, and is configured to perform a set of acts. The set of acts includes decoding a portion of audio so as to determine, for respective symbol slots of a watermark, current strength values for respective symbols. The set of acts also includes determining, for the respective symbol slots, expected symbols of an expected message. In addition, the set of acts includes determining a current score for the portion of audio using current strength values for the expected symbols and averages of current strength values for unexpected symbols. The set of acts also includes determining an accumulation score for the portion of audio using accumulated strength values for the expected symbols and averages of accumulated strength values for the unexpected symbols. And the set of acts includes, based on a detected divergence between the current score and the accumulation score, reinitializing the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols. In another aspect, a method is described. The method decoding, by a computing system, a portion of audio so as to determine, for respective symbol slots of a watermark, current strength values for respective symbols. The method also includes determining, by the computing system, for the respective symbol slots, expected symbols of an expected message. In addition, the method includes determining, by the computing system, current score for the portion of audio using current strength values for the expected symbols and averages of current strength values for unexpected symbols. The method also includes determining, by the computing system, an accumulation score for the portion of audio using accumulated strength values for the expected symbols and averages of accumulated strength values for the unexpected symbols. And the method includes, based on a detected divergence between the current score and the accumulation score, reinitializing, by the computing system, the accumulated strength values for the expected symbols and the accumulated strength values for the unexpected symbols. In another aspect, a non-transitory computer-readable medium is described. The non-transitory computer-readable medium has stored thereon instruction, that upon execution by a computing system, cause the computing system to perform a set of acts. The set of acts includes decoding a portion of audio so as to determine, for respective symbol slots of a watermark, current strength values for respective symbols. The set of acts also includes determining, for the respective symbol slots, expected symbols of an expected message. In addition, the set of acts includes determining a current score for the portion of audio usi