Method and apparatus for determining the value of samples received from bitstream data stored on a storage medium and for recovering bits of said bitstream using a Viterbi detector

摘要

DVDs have currently the highest storage density among the optical discs of practical use. Due to the high storage density the reproduced signal is deteriorated by noise caused by inter-symbol interference, crosstalk, focus error, or mastering errors. A conventional threshold bit detector generates a high bit error rate in case of low SNR. For accurate reproduction of digital data from a DVD under low SNR conditions, a specific Viterbi detector is used which performs maximum likelihood sequence estimation. It uses a variable threshold depending upon the value of the signal in the branch calculation of the metrics. <IMAGE>