Certain forms of distortion make it difficult to recover hidden data
embedded in an audio or image signal by quanitzation techniques. To
compensate for this distortion, an embedded data reader analyzes a
statistical distribution (e.g., a histogram) of feature samples (124) in
an audio or image signal suspected of having hidden auxiliary data to
derive an estimate of quantizers used to encode a reference signal (126).
The estimated quantizers then recover the reference signal (126), and the
reader uses the reference signal (126) to determine and compensate for
geometric or temporal distortion, like spatial scaling and rotation of
image data, and time scale and speed changes of audio data. After
compensating for such distortion, the reader can then more accurately
recover hidden message data using quantization techniques to extract the
message. The reference signal (126) is preferably repeated in blocks of
the image or audio data to enable synchronization at many points in an
image or audio data stream. An adaptive embedding and reading technique
is used to adaptively define the quantization bins for regions of a host
media signal based on signal statistics for each of the regions.