Methods and apparatus to perform audio watermarking and watermark detection and extraction

A computer-implemented method comprising:

• sampling an audio signal at a given time;
• based on the sampling the audio signal at the given time, extracting a first message from the audio signal;
• comparing the first message with a second message stored in a filter stack, wherein the second message is extracted at a previous time;
• based on:
• a match between the first message and the second message, and a time difference between the previous time and the given time, validating the first message;
• and
• based on the validating the first message, outputting the first message for use in audience measurement crediting.

A non-transitory computer-readable medium having stored therein instructions that, when executed by a computing system, cause the computing system to perform a set of acts comprising:

• sampling an audio signal at a given time;
• based on the sampling the audio signal at the given time, extracting a first message from the audio signal;
• comparing the first message with a second message stored in a filter stack, wherein the second message is extracted at a previous time;
• based on:
• a match between the first message and the second message, and a time difference between the previous time and the given time, validating the first message;
• and
• based on the validating the first message, outputting the first message for use in audience measurement crediting.