INDEXING BASED ON TIME-VARIANT TRANSFORMS OF AN AUDIO SIGNAL'S SPECTROGRAM

An audio identification system generates audio fingerprints and indexes associated with the audio fingerprints based on discrete and overlapping frames within a sample of an audio signal. The system applies a time-to-frequency domain transform to a time-sequence of frames, which may be filtered. The audio identification system then applies a time-variant transformation (e.g., a Discrete Cosine Transform) to the transformed frames and generates an audio fingerprint and index by selecting sets of coefficients of the time-variant transformation. The system selects coefficients that are less sensitive to possible noise and/or distortions in the underlying signal, such as low-frequency coefficients. The time-variant transformation provides sufficient sampling among the indexes by incorporating the phase information of the frames into the indexes. The system stores the audio fingerprint and other identifying information by index for efficient retrieval and matching of the retrieved fingerprints.