Methods and apparatus for performing variable black length watermarking of media
First Claim
1. A method of detecting the presence of auxiliary information in an audio signal, wherein the auxiliary information is imparted onto the audio signal by emphasizing one or more frequency components of the audio signal, the method comprising:
- sampling the audio signal to create an audio block in a buffer having a buffer size;
storing one or more components of a frequency domain representation of the audio block in a spectral characteristics table;
receiving a subsequent sample of the audio signal;
adjusting the stored components in the spectral characteristics table in accordance with elapsed time since generating the frequency domain representation to form a modified frequency domain representation;
removing a spectral effect of an oldest sample in the audio block from the modified frequency domain representation stored in the spectral characteristics table;
adding a spectral effect of the subsequent sample of the audio signal to the modified frequency domain representation stored in the spectral characteristics table to form an updated frequency domain spectrum in the spectral characteristics table;
analyzing the updated frequency domain spectrum to determine emphasis of one or more frequency components; and
determining auxiliary information corresponding to the emphasis of one or more frequency components.
10 Assignments
0 Petitions
Accused Products
Abstract
Methods, apparatus, and articles of manufacture are disclosed in which auxiliary information is added to or removed from an audio signal. In one example, the information may be added to the audio signal using at least two frequencies that are dictated by two different frequency transformation block sizes, such that the two frequencies are not fully visible when an incorrect block size is used to perform a frequency transformation. Additionally, in another example, a decoder may compensate for time and frequency affects caused by removing old samples and adding new samples, which, in one example, alleviates the need to perform repeated frequency transformation using different frequency transformation block sizes. Other examples are described.
-
Citations
28 Claims
-
1. A method of detecting the presence of auxiliary information in an audio signal, wherein the auxiliary information is imparted onto the audio signal by emphasizing one or more frequency components of the audio signal, the method comprising:
-
sampling the audio signal to create an audio block in a buffer having a buffer size; storing one or more components of a frequency domain representation of the audio block in a spectral characteristics table; receiving a subsequent sample of the audio signal; adjusting the stored components in the spectral characteristics table in accordance with elapsed time since generating the frequency domain representation to form a modified frequency domain representation; removing a spectral effect of an oldest sample in the audio block from the modified frequency domain representation stored in the spectral characteristics table; adding a spectral effect of the subsequent sample of the audio signal to the modified frequency domain representation stored in the spectral characteristics table to form an updated frequency domain spectrum in the spectral characteristics table; analyzing the updated frequency domain spectrum to determine emphasis of one or more frequency components; and determining auxiliary information corresponding to the emphasis of one or more frequency components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A decoder for detecting the presence of auxiliary information in an audio signal, wherein the auxiliary information is imparted onto the audio signal by emphasizing one or more frequency components of the audio signal, the decoder comprising:
-
a buffer having a buffer size; a sampler to sample the audio signal to create an audio block in the buffer; a memory to store one or more components of a frequency domain representation of the audio block in a spectral characteristics table; a compensator to adjust the stored components in the spectral characteristics table in accordance with elapsed time since generating the frequency domain representation to form a modified frequency domain representation; a subtractor to subtract a spectral effect of an oldest sample in the audio block from the modified frequency domain representation stored in the spectral characteristics table; an adder to add a spectral effect of a subsequent sample of the audio signal to the modified frequency domain representation stored in the spectral characteristics table to form an updated frequency domain spectrum in the spectral characteristics table; and an analyzer to analyze the updated frequency domain spectrum to determine emphasis of one or more frequency components and determine auxiliary information corresponding to the emphasis of one or more frequency components. - View Dependent Claims (11, 12, 13, 14)
-
-
15. A method of inserting auxiliary information in an audio signal, the method comprising:
-
evaluating a masking ability of a first audio block; receiving a first code; selecting a first frequency to represent the first code, wherein the first frequency is selected from a set of frequencies that are fully visible when performing a frequency transformation using a first block length, but are not fully visible when performing a frequency transformation using a second block length different from the first; synthesizing a first signal having the first frequency in accordance with the masking ability of the first audio block; combining the first signal with the first audio block; evaluating a masking ability of a second audio block; receiving a second code; selecting a second frequency to represent the second code, wherein the second frequency is selected from a set of frequencies that are fully visible when performing a frequency transformation using the second block length; synthesizing a second signal having the second frequency in accordance with the masking ability of the second audio block; and combining the second signal with the second audio block. - View Dependent Claims (16, 17, 18, 19, 20, 21)
-
-
22. An encoder for inserting auxiliary information in an audio signal, comprising:
-
a masking evaluator to evaluate a masking ability of a first audio block; a block length and index selector to receive a first code and select a first frequency to represent the first code, wherein the first frequency is selected from a set of frequencies that are fully visible when performing a frequency transformation using a first block length, but are not fully visible when performing a frequency transformation using a second block length different from the first, wherein the block length and index selector, upon receiving a second code, will select a second frequency to represent the second code, wherein the second frequency is selected from a set of frequencies that are fully visible when performing a frequency transformation using the second block length; a synthesizer to synthesize a first signal having the first frequency in accordance with the masking ability of the first audio block; and a combiner to combine the first signal with the first audio block. - View Dependent Claims (23, 24, 25, 26, 27, 28)
-
Specification