Abstract: A method and apparatus for efficiently generating complex sinusoids of a desired frequency by multiplying a phasor by a predetermined value once every sampling interval, and using the highest order bits within the phasor to identify if the phasor is at an integer multiple 45 degrees and substituting components in the phasor if it is determined that the phasor is an integer multiple of 45 degrees. If the phasor is not identified as being an integer multiple of 45 degrees then an error factor for both the real and imaginary components is determined and the real and imaginary components are corrected by removing the error factor.

Abstract: In the standard format now adapted by FCC for a digital HDTV signal, the video data symbols are interleaved and trellis encoded in accordance with a 4-state trellis code and the interleaving is of sequences of every 12 successive symbols. At the receiver the trellis decoder is therefore projected to consist of 12 respective decoder stages for the 12 interleaved sequences, each decoder stage having a branch metric calculator unit (BMC), an add-compare-select (ACS) unit and a path memory unit (PMU). The present invention separates the path memory requirements for the 12 interleaved sequences from the requisite BMC and ACS functions, so that the latter two units can provide those functions for all of the 12 interleaved sequences. A single extended PMU provides for storage of pointers to possible predecessor states of the trellis code corresponding to a present state thereof, going back to a predetermined number (such as 16) of sequentially preceding received symbol values.