MODIFYING A CODED BITSTREAM

• US 20100169349A1
• Filed: 11/02/2007
• Published: 07/01/2010
• Est. Priority Date: 03/23/2007
• Status: Active Grant

• Current Assignee: ContentArmor
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Divorra Escoda, Oscar, Zou, Dekun, Yin, Peng, Bloom, Jeffrey Adam
• Granted Patent: US 9,299,120 B2
• Time in Patent Office: Days
• US Class Current: 707/758
• CPC Class Codes: G06T 1/0035 Output size adaptive watermarking
• CPC Class Codes: G06T 2201/0053 Embedding of the watermark in the coding stream, possibly without decoding; Embedding of the watermark in the compressed domain
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 19/48 using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data motion estimation in a transform domain H04N19/547; processing of decoded motion vectors H04N19/513
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards

Abstract

Implementations may relate to various aspects of modifying, or using, a coded bitstream, or to recovering watermarking information from data. In one implementation, a coded bitstream is modified to allow for the application of a watermark to the coded bitstream without changing the coding of any other syntax elements in the bitstream. This is performed by identifying conditions necessary to change a coded syntax element without disrupting the interpretation of subsequent coded elements. The coded syntax element is replaced with another coded value if the modified value generates the same decoding variables as the original value would have generated. Particular implementations focus on syntax elements coded using entropy coding, including, for example, Context-based Adaptive Binary Arithmetic Coding (CABAC). Regardless of the type of coding or watermarking, various implementations may provide for recovering watermarking information. Particular implementations recover watermarking information using detection data and feature information.

Claims

1. A method comprising:

determining a location to check, in a digital representation of data, for watermark information;

accessing data at the determined location;

analyzing the accessed data; and

identifying the watermark information, if any, based on the analyzed data.

2. The method of claim 1 wherein:

determining the location comprises determining a frame identifier and a block identifier for a pixel-domain data representation,

accessing the data comprises accessing pixel-domain data corresponding to the frame identifier and the block identifier,

analyzing the accessed data comprises;

determining a value of a feature for the accessed data; and

comparing the determined value with a benchmark, and

identifying the watermark information comprises identifying the watermark information, if any, based on the comparison.

3. The method of claim 1 wherein determining the location comprises accessing location information from stored detection data associated with the digital representation of data.

4. The method of claim 2 wherein:

determining the frame identifier and the block identifier comprises accessing the frame identifier and the block identifier from stored detection data associated with the pixel-domain data representation, and

comparing the determined value with a benchmark comprises accessing the benchmark from the stored detection data.

5. The method of claim 1 wherein:

analyzing the accessed data comprises;

determining a value of a feature for the accessed data;

determining that a change occurred to the digital representation of data that affects more than the determined location;

adjusting the determined value to compensate for the determined change; and

comparing the adjusted value with a benchmark, and

identifying the watermark information comprises identifying the watermark information, if any, based on the comparison.

6. The method of claim 5 wherein determining that the change occurred comprises:

accessing a non-watermarked location in the digital representation of data;

determining a non-watermarked value for the feature at the non-watermarked location;

comparing the non-watermarked value to a base value; and

determining that the change occurred based on the comparison of the non-watermarked value to the base value.

7. The method of claim 6 wherein adjusting the determined value to compensate for the determined change comprises:

determining a difference between the non-watermarked value and the base value; and

adding the difference to the determined value.

8. The method of claim 6 wherein adjusting the determined value to compensate for the determined change comprises:

determining a ratio between the base value and the non-watermarked value; and

multiplying the determined value by the ratio.

9. The method of claim 6 further comprising:

accessing an identifier of the non-watermarked location from stored detection data associated with the digital representation of data; and

accessing the base value from the stored detection data.

10. The method of claim 1 wherein:

analyzing the accessed data comprises;

determining a value of a feature for the accessed data;

determining that a change occurred to the digital representation of data that affects more than the determined location;

adjusting a benchmark to compensate for the determined change; and

comparing the determined value with the adjusted benchmark, and

identifying the watermark information comprises identifying the watermark information, if any, based on the comparison.

11. The method of claim 10 wherein determining that the change occurred comprises:

accessing a non-watermarked location in the digital representation of data;

determining a non-watermarked value for the feature at the non-watermarked location;

comparing the non-watermarked value to a base value; and

determining that the change occurred based on the comparison of the non-watermarked value to the base value.

12. The method of claim 11 wherein adjusting the benchmark to compensate for the determined change comprises:

determining a difference between the non-watermarked value and the base value; and

adding the difference to the benchmark.

13. The method of claim 11 wherein adjusting the benchmark to compensate for the determined change comprises:

determining a ratio between the base value and the non-watermarked value; and

multiplying the benchmark by the ratio.

14. The method of claim 2 wherein the feature includes at least one of mean luminance or variance.

15. The method of claim 1 wherein:

the digital representation of data comprises an encoded bitstream, and

determining the location comprises determining a bit location in the encoded bitstream.

16. The method of claim 1 wherein identifying the watermark information comprises determining a value for a bit of a payload.

17. The method of claim 1 wherein the payload is a one-bit payload.

18. The method of claim 16 further comprising repeating the operations of determining, accessing, analyzing, and identifying one or more times to determine all of the bits of the payload.

19. An apparatus comprising a processing device configured to perform at least the following:

determining a location to check, in a digital representation of data, for watermark information;

accessing data at the determined location;

analyzing the accessed data; and

identifying the watermark information, if any, based on the analyzed data.

20. An apparatus comprising:

means for performing at least the following;

determining a location to check, in a digital representation of data, for watermark information,

accessing data at the determined location,

analyzing the accessed data, and

identifying the watermark information, if any, based on the analyzed data; and

means for storing the accessed data.

21. An apparatus comprising a processor-readable medium including instructions stored on the processor-readable medium for performing at least the following:

determining a location to check, in a digital representation of data, for watermark information;

accessing data at the determined location;

analyzing the accessed data; and

identifying the watermark information, if any, based on the analyzed data.