Audio processing system and method
An audio system and method is described to monitor whether the audio processing performed on an audio signal is corrupted. The audio system includes module to embed a watermark into an audio signal, and a verification module to verify the presence of the watermark after the audio processing has been performed. The embedding strength of the watermark can be adjusted on the basis of whether the presence of the watermark is detected. The embedding strength for the watermark may be adjusted such that it is as low as possible while still allowing detection, thus keeping the audio quality as high as possible.
1 . A method of processing an audio signal comprising:
receiving an audio signal;
watermarking, by an embedding module, the audio signal with a watermark having an embedding strength value to produce a watermarked audio signal and outputting the watermarked audio signal;
processing, by an audio processor, the watermarked audio signal, and outputting a processed watermarked audio signal;
determining a presence of the watermark in the processed watermarked audio signal containing the audio signal and the watermark;
adapting the embedding strength value of the watermark, by a verification module, to produce an adapted embedding strength value, dependent on a presence or an absence of the watermark in the processed watermarked audio signal; and
watermarking, by the embedding module, the processed watermarked audio signal containing the audio signal and the watermark with an enhanced watermark having an adapted embedding strength value, and outputting the watermarked processed audio signal having the enhanced watermark.
2 . The method of claim 1 , wherein watermarking the audio signal further comprises:
generating the watermark by delaying the audio signal to produce a delayed audio signal, and multiplying the delayed audio signal with the embedding strength value; and
adding the watermark to the audio signal.
3 . The method of claim 2 , wherein determining the presence of the watermark further comprises:
determining an auto-cepstrum of a plurality of samples of the processed watermarked audio signal, the plurality of samples corresponding to a time segment having a duration greater than a delay time of the delayed audio signal;
determining an echo cepstral coefficient by determining a cepstral coefficient corresponding to the delay time; and
determining whether the watermark is present from a value of the echo cepstral coefficient.
4 . The method of claim 3 , wherein determining the presence of the watermark further comprises:
determining the auto-cepstrum of a plurality of samples of the processed audio signal for a plurality of time segments;
determining the echo cepstral coefficient for each time segment;
determining an average value of the echo cepstral coefficients; and
determining whether the watermark is present from the average value of the echo cepstral coefficients.
5 . The method of claim 1 wherein watermarking the audio signal comprises:
generating an ultrasound reference signal;
multiplying the ultrasound reference signal with the embedding strength value resulting in a modified ultrasound reference signal; and
adding the modified ultrasound reference signal to the audio signal.
6 . The method of claim 1 further comprising:
receiving the processed watermarked audio signal; and
determining the presence of the watermark in the processed watermarked audio signal; and, in response to the watermark not being present, generating an indication that the processed watermarked audio signal is corrupted.
7 . The method of claim 1 further comprising: in response to the watermark not being present, increasing the embedding strength value, and in response to the watermark being present, decreasing the embedding strength value.
8 . The method of claim 1 further comprising: in response to the watermark not being present, comparing the embedding strength value with a reference embedding strength value and generating an indication that the processed watermarked audio signal is corrupted in response to the embedding strength value exceeding the reference embedding strength value.
9 . The method of claim 1 , wherein the processed watermarked audio signal comprises a plurality of audio channels and wherein verifying the presence of the watermark further comprises determining whether the watermark is present in at least one audio channel of the processed watermarked audio signal.
10 . A method of audio alert signal generation for an automotive audio system, comprising the method of claim 1 .
11 . A non-transitory computer readable media comprising a computer program comprising computer executable instructions which, when executed by a computer, causes the computer to perform a method of receiving an audio signal;
watermarking, by an embedding module, the audio signal with a watermark, to produce a watermarked audio signal, having an embedding strength value and outputting the watermarked audio signal;
processing, by an audio processor, the watermarked audio signal, and outputting a processed watermarked audio signal;
determining a presence of the watermark in the processed watermarked audio signal containing the audio signal and the watermark;
adapting the embedding strength value of the watermark, by a verification module, to produce an adapted embedding strength value, dependent on a presence or an absence of the watermark in the processed watermarked audio signal; and
watermarking, by the embedding module, the processed watermarked audio signal containing the audio signal and the watermark with an enhanced watermark having an adapted embedding strength value, and outputting the watermarked processed audio signal having the enhanced watermark.
12 . An audio processing system comprising:
an audio processing module having an audio processing module input and an audio processing module output;
a watermarking module comprising:
an embedding module having an embedding module input configured to receive an audio signal, an embedding module control input configured to receive an embedding strength value, and an embedding module output coupled to the audio processing module input;
a verification module having a verification module input coupled to the audio processing module output and a verification module control output coupled the embedding module control input; wherein
the embedding module is further configured to:
receive an audio signal;
watermark the audio signal with a watermark having the embedding strength value to produce a watermarked audio signal, and output the watermarked audio signal;
the audio processing module is further configured to process the watermarked audio signal containing the audio signal and the watermark to produce a processed watermarked audio signal, and output the processed watermarked audio signal;
the verification module is further configured to determine a presence of the watermark in the processed watermarked audio signal containing the audio signal and the watermark; and adapt the embedding strength value of the watermark embedded by the embedding module in response to the verification module control output, dependent on the presence or an absence of the watermark in the processed watermarked audio signal; and
the embedding module is further configured to embed the watermarked processed audio signal with an enhanced watermark.
13 . The audio processing system of claim 12 , wherein the embedding module is further configured to generate the watermark by:
delaying the audio signal to produce a delated audio signal, multiplying the delayed audio signal with the embedding strength value; and
adding the watermark to the audio signal.
14 . The audio processing system of claim 13 , wherein the verification module is further configured to:
determine an auto-cepstrum of a plurality of samples of the processed watermarked audio signal for a plurality of time segments;
determine the echo cepstral coefficient for each time segment;
determine an average value of the echo cepstral coefficients; and;
determine whether the watermark is present from the average value of the echo cepstral coefficients.
15 . The audio processing system of claim 12 , wherein the verification module is further configured to:
determine an auto-cepstrum of a plurality of samples of the processed watermarked audio signal, the plurality of samples corresponding to a time segment having a duration greater than a delay time of a delayed audio signal;
determine an echo cepstral coefficient by determining a cepstral coefficient corresponding to the delay time; and
determine whether the watermark is present from a value of the echo cepstral coefficient.
16 . The audio processing system of claim 12 , wherein the embedding module is further configured to generate the watermark by:
generating an ultrasound reference signal;
multiplying the ultrasound reference signal with the embedding strength value resulting in a modified ultrasound reference signal; and
adding the modified ultrasound reference signal to the audio signal.
17 . The audio processing system of claim 12 , wherein the verification module further comprises a verification status output and is further configured to:
generate an indication that the processed watermarked audio signal is corrupted on the verification status output in response to the watermark not being present.
18 . The audio processing system of claim 17 , wherein the verification module is further configured to in response to the watermark not being present, compare the embedding strength value with a reference embedding strength value generate the indication that the processed watermarked audio signal is corrupted in response to the embedding strength value exceeding the reference embedding strength value.
19 . The audio processing system of claim 12 , wherein the verification module is further configured to increase the embedding strength value in response to the watermark not being present, and to decrease the embedding strength value in response to the watermark being present.
20 . The audio processing system of claim 12 , wherein the processed watermarked audio signal comprises a plurality of audio channels and wherein the verification module is further configured to determine whether the watermark is present in at least one audio channel of the processed watermarked audio signal.