EP2439735A1 - Procédé et appareil pour générer des motifs de phase de référence - Google Patents

Procédé et appareil pour générer des motifs de phase de référence Download PDF

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Publication number
EP2439735A1
EP2439735A1 EP10306091A EP10306091A EP2439735A1 EP 2439735 A1 EP2439735 A1 EP 2439735A1 EP 10306091 A EP10306091 A EP 10306091A EP 10306091 A EP10306091 A EP 10306091A EP 2439735 A1 EP2439735 A1 EP 2439735A1
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EP
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Prior art keywords
blocks
frequency domain
audio signal
windowing
subblocks
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EP10306091A
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German (de)
English (en)
Inventor
Xiao-ming CHEN
Michael Arnold
Peter Georg Baum
Ulrich Gries
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Thomson Licensing SAS
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Thomson Licensing SAS
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Priority to EP10306091A priority Critical patent/EP2439735A1/fr
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
    • G10L19/018—Audio watermarking, i.e. embedding inaudible data in the audio signal
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
    • G10L19/02—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using spectral analysis, e.g. transform vocoders or subband vocoders
    • G10L19/022—Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring

Definitions

  • the invention relates to a method and to an apparatus for generating reference phase patterns to be used for controlling watermarking by frequency domain phase modulation of spectra of an audio signal.
  • watermark embedding occurs in the phase domain by modifying phases of the host signal spectrum according to phase reference patterns. Specifically, the host audio signal is split into blocks of length L B and each block is used for embedding a watermark symbol. The watermark message is represented by a sequence of symbols. For embedding, each block can be further partitioned into N SB overlapping subblocks of L SB samples length with an overlap length of L SB /2.
  • phase of the weighted subblock spectrum are modified according to generated reference phases and according to results from a psycho-acoustic analysis of the host audio signal.
  • reference phases for each watermark message symbol are generated by the following steps:
  • Step B3) mimics the windowing-overlap process that is commonly used in the analysis stage of digital audio signal processing.
  • a windowing function is selected such that an ideal reconstruction is guaranteed following ideal analysis (windowing-overlap) and synthesis (windowing-overlap-add) processes.
  • generated reference angles in step B4) are employed to modify host audio spectrum phases after the host signal has undergone the windowing-overlap processing.
  • phase generation processing is that many IDFTs/DFTs are required, which imposes constraints on the achievable speed of hardware/software implementations, and the deployment of related audio watermarking schemes is therefore limited for real-time applications.
  • IDFTs/DFTs are required, which imposes constraints on the achievable speed of hardware/software implementations, and the deployment of related audio watermarking schemes is therefore limited for real-time applications.
  • the audio content is watermarked with a label that identifies the customer.
  • a copyright owner will license multiple different works to the customer.
  • different keys for individual copyrighted works are used. Therefore efficient reference phase generation is a necessary prerequisite for deploying an audio watermarking scheme in such application scenario.
  • a problem to be solved by the invention is to provide more efficient generation of the reference phase patterns. This problem is solved by the method disclosed in claim 1. An apparatus that utilises this method is disclosed in claim 6.
  • the efficient generation of random reference phase patterns is carried out by approximating the inverse transform of the phase reference patterns, and the corresponding forward transform and the windowing and windowing-overlapping effects using two different short-length frequency-domain filters for even and odd blocks or subblocks.
  • the computational complexity for generating the reference phase pattern blocks or subblocks for frequency domain phase modulation of the audio signal blocks or subblocks is significantly reduced, which in turn reduces the complexity of both watermark embedder at sender side and watermark detector at receiver side.
  • the inventive reference phase generation fulfils critical real-time requirements and enables a wide deployment of corresponding audio watermarking processings.
  • the flexibility of controlling the generated phases is maintained, e.g. in case structured phases are used instead of random ones.
  • the inventive method is suited for generating reference phase patterns to be used for controlling watermarking by frequency domain phase modulation of spectra of an audio signal, said method including the steps:
  • the inventive apparatus is suited for generating reference phase patterns to be used for controlling watermarking by frequency domain phase modulation of spectra of an audio signal, said apparatus including:
  • an audio signal block a is partitioned into N SB overlapped (50% overlapping) subblocks of length L SB denoted as ⁇ a m , 0 ⁇ m ⁇ N SB ⁇ . Accordingly, the even subblocks are non-overlapping and each odd subblock can be obtained by its two adjacent even subblocks. Specifically, the (2 i +1)-th (i.e.
  • the phases of spectra of windowed subblocks a w,m serve as reference phases for the watermark embedding, followed by DFT for the weighted subblocks to get reference spectra.
  • ⁇ A m [ k ], 0 ⁇ k ⁇ L SB -1 ⁇ and ⁇ W [ k ], 0 ⁇ k ⁇ L SB -1 ⁇ shall denote DFTs for the m-th subblock a m and for the windowing function, respectively.
  • the first term in Eq.(4) is the contribution from two spectral lines of the same index within two adjacent subblocks and the second term is the contribution from other spectral lines.
  • the reference spectrum for an odd subblock is obtained by inserting Eq.(4) into Eq.(2). Therefore, for the evaluation of reference spectra, two frequency-domain filters ⁇ F [ k ] ⁇ and ⁇ W [ k ] ⁇ are involved. In case they can be well-approximated by a few filter taps, an efficient evaluation of reference spectra is feasible.
  • the spectrum of the windowing function can also be approximated by a few dominant components.
  • the second term in Eq.(9) can be interpreted as the spectrum difference that passes through two filters, which can be regarded as representing in total a single filter:
  • L SB ⁇ q - L w L w - 1 k + q 2 ⁇ A 2 ⁇ i ⁇ ⁇ k + q > + A 2 ⁇ i + 2 ⁇ ⁇ k + q > ⁇ W ⁇ q > + 1
  • L SB 2 ⁇ q - L g L g - 1 k + q ⁇ A 2 ⁇ i ⁇ ⁇ k + q > - A 2 ⁇ i + 2 ⁇ ⁇ k + q > ⁇ G ⁇ q >
  • L g L w + L 1 .
  • Eq.(8) and Eq.(10) provide an efficient evaluation of the reference spectra, whereby only two frequency-domain filters ⁇ W [ ⁇ q >] ⁇ and ⁇ G [ ⁇ q >] ⁇ with a few dominant taps are required.
  • the corresponding filter coefficients can be pre-calculated, and the approximation accuracy can be controlled by filter length parameters L w and L g . That is, the trade-off between robustness and computational complexity can be adjusted by choosing different L w and L g values.
  • the original processing employing FFTs/IFFTs requires on average 62 real-value multiplications and 62 real-value additions for the evaluation of each DFT coefficient of the reference spectra.
  • a received audio signal AS is sampled in an acquisition or receiving section step or stage 51, and thereafter passes through a segmentation, windowing and DFT step or stage 52 to a phase modulation step or stage 53, in which the phases are modulated within the frequency domain using references patterns or phases from a block 56.
  • a corresponding IDFT, windowing and overlap-add step or stage 54 is passed, which outputs the watermarked audio signal WAS.
  • the phase value modification can be controlled according to results from a psycho-acoustic analysis of the audio signal AS.
  • a secret key SK is used to generate pseudo-random phases in a step or stage 55, which controls a reference pattern or phase generation step or stage 56 that operates using the above-described inventive processing.
  • stage 56 does not include IDFT, windowing, DFT and overlap+add, but instead approximates these functions by a first frequency domain filtering by W for even subblocks and a different second frequency domain filtering by W and G for odd subblocks, thereby generating approximated versions of reference phase patterns for the audio signal subblocks.
  • step 60 nSymbols, nSubBlocks and the secret key SK are input.
  • running variable 'j' is set '0' and in step 612 running variable 'i' is set '0'.
  • step 62 (which is included in step/stage 55 in Fig. 5 ) a random phase is generated for subblocks 2i and 2i+2.
  • step 63 the spectra are constructed from the phases, whereby the magnitude equals '1'.
  • step 64 the WOL subblock 2i+1 and the WIN subblocks 2i and 2i+2 are calculated. Steps 63 and 64 are included in step/stage 56 in Fig. 5 .
  • step 65 'i' is incremented by '1'.
  • the running variable 'j' is incremented by '1' in step 67. If 'j' has reached value (nSymbols-1) in step 68, nSubBlocks reference spectra for nSymbols are output in step 69.
  • the order of even and odd subblocks is exchanged.
  • a combination of frequency-domain convolution and IDFT-windowing-DFT can be employed for the phase generation.
  • Eq.(8) is used for generating the reference spectra for an even subblock Eq.(8).
  • Eq.(10) is realised as a frequency-domain convolution
  • IDFT-windowing-DFT a time-domain subblock corresponding to ⁇ A 2i [ k ] - A 2i+2 [ k ] ⁇ is obtained via IDFT, and is thereafter weighted by a time-domain filter corresponding to ⁇ G [ k ] ⁇ .
  • the reference spectrum of the odd subblock is obtained by a DFT of the weighted subblock.
  • Such alternative processing typically has a higher computational complexity than the inventive processing described before but a lower complexity than the processing described in the background section, because the IDFT-windowing-DFT is applied to odd blocks only.

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  • Engineering & Computer Science (AREA)
  • Computational Linguistics (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • Human Computer Interaction (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
EP10306091A 2010-10-06 2010-10-06 Procédé et appareil pour générer des motifs de phase de référence Withdrawn EP2439735A1 (fr)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014062332A1 (fr) * 2012-10-16 2014-04-24 The Nielsen Company (Us), Llc Procédés et appareils pour exécuter une détection et une extraction d'un tatouage numérique audio
US9596521B2 (en) 2014-03-13 2017-03-14 Verance Corporation Interactive content acquisition using embedded codes
US9639911B2 (en) 2014-08-20 2017-05-02 Verance Corporation Watermark detection using a multiplicity of predicted patterns
US9769543B2 (en) 2014-11-25 2017-09-19 Verance Corporation Enhanced metadata and content delivery using watermarks
US9942602B2 (en) 2014-11-25 2018-04-10 Verance Corporation Watermark detection and metadata delivery associated with a primary content
CN108417199A (zh) * 2013-01-18 2018-08-17 株式会社东芝 音频水印信息检测装置及音频水印信息检测方法
US10277959B2 (en) 2014-12-18 2019-04-30 Verance Corporation Service signaling recovery for multimedia content using embedded watermarks
US10504200B2 (en) 2014-03-13 2019-12-10 Verance Corporation Metadata acquisition using embedded watermarks
US11722741B2 (en) 2021-02-08 2023-08-08 Verance Corporation System and method for tracking content timeline in the presence of playback rate changes

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007031423A1 (fr) 2005-09-16 2007-03-22 Thomson Licensing Filigranage inaudible de signaux audio faisant appel a des modifications de phase

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Publication number Priority date Publication date Assignee Title
WO2007031423A1 (fr) 2005-09-16 2007-03-22 Thomson Licensing Filigranage inaudible de signaux audio faisant appel a des modifications de phase

Non-Patent Citations (3)

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Title
FERRIS T L J ET AL: "Frequency domain method for windowing in Fourier analysis", ELECTRONICS LETTERS, vol. 28, no. 15, 16 July 1992 (1992-07-16), pages 1440, XP002626131, ISSN: 0013-5194, DOI: 10.1049/el:19920916 *
M.ARNOLD; P.G.BAUM; W.VOESSING: "A phase modulation audio watermarking technique", LLTH INFORMATION HIDING WORKSHOP, 2009, pages 102 - 116
MICHAEL ARNOLD ET AL: "A Phase Modulation Audio Watermarking Technique", 8 June 2009, INFORMATION HIDING, SPRINGER BERLIN HEIDELBERG, BERLIN, HEIDELBERG, PAGE(S) 102 - 116, ISBN: 978-3-642-04430-4, XP019129276 *

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9368123B2 (en) 2012-10-16 2016-06-14 The Nielsen Company (Us), Llc Methods and apparatus to perform audio watermark detection and extraction
WO2014062332A1 (fr) * 2012-10-16 2014-04-24 The Nielsen Company (Us), Llc Procédés et appareils pour exécuter une détection et une extraction d'un tatouage numérique audio
CN108417199B (zh) * 2013-01-18 2022-11-22 株式会社东芝 音频水印信息检测装置及音频水印信息检测方法
CN108417199A (zh) * 2013-01-18 2018-08-17 株式会社东芝 音频水印信息检测装置及音频水印信息检测方法
US10110971B2 (en) 2014-03-13 2018-10-23 Verance Corporation Interactive content acquisition using embedded codes
US9596521B2 (en) 2014-03-13 2017-03-14 Verance Corporation Interactive content acquisition using embedded codes
US9681203B2 (en) 2014-03-13 2017-06-13 Verance Corporation Interactive content acquisition using embedded codes
US10504200B2 (en) 2014-03-13 2019-12-10 Verance Corporation Metadata acquisition using embedded watermarks
US10499120B2 (en) 2014-03-13 2019-12-03 Verance Corporation Interactive content acquisition using embedded codes
US9854332B2 (en) 2014-03-13 2017-12-26 Verance Corporation Interactive content acquisition using embedded codes
US9854331B2 (en) 2014-03-13 2017-12-26 Verance Corporation Interactive content acquisition using embedded codes
US10445848B2 (en) 2014-08-20 2019-10-15 Verance Corporation Content management based on dither-like watermark embedding
US10354354B2 (en) 2014-08-20 2019-07-16 Verance Corporation Content synchronization using watermark timecodes
US9805434B2 (en) 2014-08-20 2017-10-31 Verance Corporation Content management based on dither-like watermark embedding
US9639911B2 (en) 2014-08-20 2017-05-02 Verance Corporation Watermark detection using a multiplicity of predicted patterns
US10178443B2 (en) 2014-11-25 2019-01-08 Verance Corporation Enhanced metadata and content delivery using watermarks
US9942602B2 (en) 2014-11-25 2018-04-10 Verance Corporation Watermark detection and metadata delivery associated with a primary content
US9769543B2 (en) 2014-11-25 2017-09-19 Verance Corporation Enhanced metadata and content delivery using watermarks
US10277959B2 (en) 2014-12-18 2019-04-30 Verance Corporation Service signaling recovery for multimedia content using embedded watermarks
US11722741B2 (en) 2021-02-08 2023-08-08 Verance Corporation System and method for tracking content timeline in the presence of playback rate changes

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