Abstract: In order to correct for common phase error in demodulated digital video broadcast signals which comprise data modulated on a multiplicity of spaced carrier frequencies, a demodulator includes analog to digital conversion means (20) for providing a series of digital samples of the broadcast signal, real to complex conversion means (22) for converting each digital sample to a complex number value, Fourier Transform means (24) for analysing the complex number values to provide a series of data signal values in complex number format for each carrier frequency, and signal processing means for processing the series of data signal values including phase error correcting means (30), the phase error correcting means including means for converting the data signal values from a complex number format to a phase angle format, means for determining a common phase error by assessing the phase of continual pilot signals in the broadcast signals and determining the variation in phase of the continual pilot signals between c

Abstract: Video signals are sampled at 4Fsc locked onto sub-carrier phase and frequency. The active picture lines of each field are divided into 6 blocks of 47 lines and the active line periods of those lines scrambled on a block by block basis by line order shuffling. The shuffling algorithm is generated by a line shuffling permutator driven by a PRBS generator (controls 36, 38). Active line period samples for one block are written in unscrambled form into a first memory block (32) and samples from the previous block are read out in scrambled form from a second memory block (34) for transmission. The complementary process takes place in the decoder.