Robust watermark for DSD signals

• US 20030079131A1
• Filed: 09/05/2002
• Published: 04/24/2003
• Est. Priority Date: 09/05/2001
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Reefman, Derk
• Granted Patent: US 7,325,131 B2
• Time in Patent Office: Days
• US Class Current: 713/176
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00891 embedded in audio data
• CPC Class Codes: G11B 20/00913 based on a spread spectrum technique
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: H04H 20/31 using in-band signals, e.g. subsonic or cue signal

Abstract

A robust watermark embedded into a Direct Stream Digital (DSD) audio signal including a flat frequency response in a specific frequency range which does not extend below 20 kHz or above 100 kHz. The watermark is therefore hidden in the noise spectrum of the DSD signal, such that the watermark is inaudible to a listener. Since the noise spectrum contains important information that helps provide the DSD signals with sharp transients and an accurate impulse response, the watermark cannot be removed from the DSD signal without causing significant degradation to the signal'"'"'s audio quality.

Claims

1. A method comprising:

inserting a watermark into a Direct Stream Digital (DSD) signal to create a watermarked signal, said inserted watermark being spread across a frequency range of said watermarked signal.

2. The method of claim 1, wherein said frequency range does not extend substantially below 20 kHz.

3. The method of claim 1, wherein said frequency range does not extend substantially above 100 kHz.

4. The method of claim 1, wherein said frequency range does not extend substantially below 20 kHz and does not extend substantially above 100 kHz.

5. The method of claim 1, wherein said inserting step is performed using a spread spectrum watermarking process.

6. The method of claim 1, wherein prior to said inserting step, a soft watermark is inserted into said DSD signal by replacing selected bits of said DSD signal with bits corresponding to soft watermark data.

7. A method comprising:

inserting a watermark into an analog signal to create a watermarked signal, said inserted watermark being spread across a frequency range of said watermarked signal;

converting said watermarked signal into a Direct Stream Digital (DSD) signal.

8. A Direct Stream Digital (DSD) signal including an embedded watermark, which is spread across a frequency range of said DSD signal.

9. A data storage medium having stored thereon a DSD signal as claimed in claim 8.

10. A recording apparatus (100) comprising:

a modulator (40) for converting an input signal into a Direct Stream Digital (DSD) signal;

a watermark embedder (20) for embedding a watermark into said DSD signal and outputting a watermarked signal, such that said watermark is spread across a frequency range of said watermarked signal; and

a recorder (50) for recording said watermarked signal on a storage medium.

11. The recording apparatus (100) of claim 10, wherein said watermark embedder (20) utilizes a spread spectrum watermarking (SSW) technique, said watermark embedder (20) further comprising

a pseudo noise generator (22) for generating pseudo noise;

a modulator (24) for modulating said watermark with said pseudo noise to generate a modulated watermark signal;

an amplifier (26) for scaling the modulated watermark signal; and

an addition element (28) for combining the DSD signal with the scaled modulated watermark signal.

12. A recording apparatus (100) comprising:

a watermark embedder (20) for embedding a watermark into an analog signal and outputting a watermarked signal, such that said watermark is spread across a frequency range of said watermarked signal;

a modulator (40) for converting said watermarked signal into a Direct Stream Digital (DSD) signal; and

a recorder (50) for recording said DSD signal on a storage medium.