New patents are issued by the USPTO on Tuesdays. Both of today's Spotlight Patents concern aspects of digital watermarking. Assigned to Nielsen, the first of today's patents addresses techniques for down-mixing compensation for audio watermarking. Assigned to DivX, the second patent addresses techniques for session based watermarking of media content using encrypted content streams.
9,514,760, "Down-mixing compensation for audio watermarking," assigned to The Nielsen Company.
Example methods, apparatus, systems and articles of manufacture to implement down-mixing compensation for audio watermarking are disclosed. Example watermark embedding methods disclosed herein include determining respective attenuation factors for a plurality of audio bands based on energy values associated with down-mixed audio samples corresponding to a first audio channel of a multi-channel audio signal and a second audio channel of the multi-channel audio signal. Disclosed example watermark embedding methods also include embedding a watermark in audio samples of the first audio channel based on the attenuation factors.
9,516,359, "Session based watermarking of media content using encrypted content streams," assigned to DivX.
Methods for session based watermarking of media content using encrypted content streams are provided. At least two content streams of the same media content are watermarked with different watermark information and encrypted using different encryption percentages. During a playback session, a unique sequence is generated and provided to a client device for use by the client device in selecting consecutive content segments from the different content streams to produce the original media content with a watermark that uniquely identifies a user of the client device. When selecting the different content segments, the client device compares the encryption percentage of certain selected content segments with the expected encryption percentage for those content segments to determine whether the content streams have been tampered with.