Abstract: Determining a chrominance portion to be watermarked employs a perception-based table that indicates for various pixel values which of the chrominance portions, if any, should be selected for watermarking. Only the Y, U, and V values of a pixel are needed to access the table and determine which chrominance portion should be selected. However, the table may be represented such that it may be accessed using only R, G, and B values. The table may be modified so that it may indicate which of U or V should be selected, or that neither should be selected, indicating that this pixel should not be watermarked at all. Advantageously, the table may be simplified by employing some processing, because a large section of the table may be replaced by a simple test on the pixel values, e.g., U<128, to determine the selected chrominance portion.

Abstract: A method and apparatus are disclosed for increasing the time and frequency diversity of a multi-stream signal in a DAB system. A plurality of audio streams are divided into four (4) digital sub-streams, C00, C01, C10, and C11. Each sub-stream C00, C01, C10, and C11 is assigned a unique frequency band, and time slot. A first core sub-stream C10 is mapped to one frequency partition and a second core sub-stream C00 is mapped to another frequency partition and delayed relative to the first core sub-stream. Similarly, two enhancement sub-streams C11 and C01 are mapped to different frequency partitions and are time delayed relative to each other and the core sub-streams. The two core sub-streams C00 and C10 can have a maximum separation across both the time and frequency axes. Each core sub-stream C00 and C10 is separate from one of the enhancement sub-streams in the frequency domain and separate in the time domain from the other enhancement sub-stream.

Abstract: Data to be impressed upon the average value of a chrominance portion of a block, is replicated at least once. The original and each replica is impressed on blocks in the same block position of separate frames. The frames that have like-positioned blocks that are carrying the same data are considered to be a group. Specific blocks of the frame may be embedded with a particular known data sequence rather than user data. Each group may employ a different known sequence. Instead of simply repeating the data for each like-positioned block of a group, the amount added to the average value for each such block may be changed slightly from frame to frame in group, even when the complexity of the blocks is the same. At a receiver, the multiple instances of the same data bit are extracted and combined to form a single received bit.

Abstract: Determining a chrominance portion to be watermarked employs a perception-based table that indicates for various pixel values which of the chrominance portions, if any, should be selected for watermarking. Only the Y, U, and V values of a pixel are needed to access the table and determine which chrominance portion should be selected. However, the table may be represented such that it may be accessed using only R, G, and B values. The table may be modified so that it may indicate which of U or V should be selected, or that neither should be selected, indicating that this pixel should not be watermarked at all. Advantageously, the table may be simplified by employing some processing, because a large section of the table may be replaced by a simple test on the pixel values, e.g., U<128, to determine the selected chrominance portion.

Abstract: Watermark data is effectively placed in at least one of the bit positions, e.g., of the integer portion, of the average value of at least a selected one of the chrominance portions of up to each block, on up to a frame-by-frame basis. Values of the selected chrominance portion of individual pixels in a block may be adjusted if necessary in order to cause the resulting substitution of the selected bit of the average. The bit position replaced may be a function of the block's busyness. A “margin” value may also be added to the average value in order to better ensure that the bit of watermark data survives any MPEG encoding, while minimizing resulting artifacts. A receiver extracts the bit of watermark data from the selected bit position of the average value of the chrominance portion.

Abstract: A receiver for receiving synchronized digital transmissions organized in frames, each frame having a frame start, has a clock for generating pulses at time intervals with respect to a time reference and a counter for generating a count of the time intervals with respect to the time reference. A/D converters sample the digital transmission using the pulses from the clock. A cyclic prefix correlator detects the frame start during a count corresponding to an A/D sample. This count is indicative of the time interval during which the frame start was detected with respect to the reference. A memory is provided for storing a plurality (typically 36) counts indicative of the time interval during which the frame start was detected. A pointer is generated from the counts stored in memory. The pointer is indicative of a projected time interval during which a future frame start is expected to arrive.