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Forensic detection of parametric audio coding schemes

A technology for encoding, decoding and audio signals, which is applied in the field of audio forensics and can solve problems such as total bit rate reduction

Inactive Publication Date: 2014-01-29
DOLBY LAB LICENSING CORP +1
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  • Abstract
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AI Technical Summary

Problems solved by technology

As a result, over the entire frequency band of the audio signal, the overall bit rate can be significantly reduced compared to ordinary AAC waveform coding

Method used

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  • Forensic detection of parametric audio coding schemes
  • Forensic detection of parametric audio coding schemes
  • Forensic detection of parametric audio coding schemes

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Embodiment Construction

[0065] As outlined above, in MPEG SBR encoding, an audio signal is waveform encoded at a reduced sampling rate and bandwidth. The lost higher frequencies are reconstructed in the decoder by copying the low frequency part to the high frequency part using the sent side information. The transmitted incidental information (eg spectral envelope parameters, noise parameters, tone addition / removal parameters) is applied to the patches from the low-band signal, where these patches have been copied up or transposed to higher frequencies. As a result of this copy-up process, there should be a correlation between certain spectral parts of the low-band signal and spectral parts of the high-band signal that are copied up. These correlations may be the basis for detecting band-replication based coding within the decoded audio signal.

[0066]The correlation between the spectral part of the low-band signal and the spectral part of the high-band signal may have been reduced or removed by app...

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Abstract

The present document relates to audio forensics, notably the blind detection of traces of parametric audio encoding / decoding. In particular, the present document relates to the detection of parametric frequency extension audio coding, such as spectral band replication (SBR) or spectral extension (SPX), from uncompressed waveforms such as PCM (pulse code modulation) encoded waveforms. A method for detecting frequency extension coding history in a time domain audio signal is described. The method may comprise transforming the time domain audio signal into a frequency domain, thereby generating a plurality of subband signals in a corresponding plurality of subbands comprising low and high frequency subbands; determining a degree of relationship between subband signals in the low frequency subbands and subband signals in the high frequency subbands; wherein the degree of relationship is determined based on the plurality of subband signals; and determining frequency extension coding history if the degree of relationship is greater than a relationship threshold.

Description

[0001] Cross References to Related Applications [0002] This application claims priority to US Patent Provisional Application No. 61 / 488,122, filed May 19, 2011, which is hereby incorporated by reference in its entirety. technical field [0003] The present application relates to audio forensic, in particular blind detection of traces of parametric audio encoding / decoding in audio signals. In particular, the application relates to the detection of parametric stereo coding from uncompressed waveforms, such as PCM (Pulse Code Modulation) encoded waveforms, and / or parametric frequency-extended audio coding, such as spectral band replication (SBR) or spectrum extension (SPX)) detection. Background technique [0004] HE-AAC (High Efficiency-Advanced Audio Codec) is a high-efficiency music audio codec for low and moderate bitrates (eg, 24-96kb / s for stereo content). In HE-AAC, the audio signal is down-sampled by a factor of 2, and the resulting low-band signal is AAC waveform-c...

Claims

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Application Information

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IPC IPC(8): G10L19/008G10L21/038
CPCG10L19/008G10L21/038G10L19/00G10L19/12G10L21/02G10L25/03
Inventor H·H·蒙特A·比斯沃斯R·拉达克里希南
Owner DOLBY LAB LICENSING CORP
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