Kornelis A. Schouhamer Immink

On the application of sequence estimation algorithms in the digital compact cassette (DCC)

In the current digital compact cassette (DCC) recorder, a straightforward threshold detection scheme is applied which does not exploit the distance properties of the 8-to-10 modulation (ETM) code. More advanced detection schemes are investigated to see if they improve system performance. Two soft decision sequence estimation algorithms are considered: a fully-fledged Viterbi algorithm realizing maximum likelihood sequence estimation (MISE) and a suboptimal trellis detection algorithm. With either of the algorithms, an asymptotic gain of 3 dB versus threshold detection level in the presence of additive white Gaussian noise (AWGN) is expected. The suboptimal detection algorithm is based on the running digital sum (RDS) trellis underlying the ETM code. Performing the suboptimal algorithm requires a minimum of 48 additions, 19 comparisons, and a single table look-up for both detection and decoding of an ETM codeword, versus a minimum of 4234 additions, 421 comparisons, and 423 table look-ups for the fully-fledged algorithm. Compared to the fully-fledged scheme, the suboptimal algorithm leads to a large reduction in computational complexity. The performance of either of the algorithms in the presence of AWGN is determined by means of a computer simulation. The fully-fledged Viterbi algorithm achieves a gain of about 2.3 dB versus threshold detection level for symbol error rates in the order of 10/sup -4/ to 10/sup -5/. >

A comparison of rotary- and stationary-head video tape recorders

In magnetic tape recording, two approaches have emerged in which essentially the same medium is tracked in two different ways: rotary- and stationary-head recorders. Both approaches are commonly employed in digital audio and data recording, but since the introduction of the first analog video recorders in the early 50s, rotary-head recorders (either helical or transverse scan) have held undivided sway in the video domain. The advent of various new enabling techniques such as (MPEG) source coding and multi-trade heads may affect the hegemony of the rotary-head machine. The article appraises both types of transport in an attempt to establish which approach might be considered for a given application.

System Requirements of a Stationary-head Multi-track Recorder

4.76 cm/sec 3.78 mm 96 kbit/sec 185 pm 70 pm. Abstract We report on the design considerations of a stationary-head multi-track magnetic recorder. The particular reasons for adopting the rate 8/10, dc-free recording code, the full-response detection method, and the clock recovery will be detailed. Implementation issues of the channel chip, particularly related to cost and power consumption, will be addressed. A new multi-track Phase-Lock Loop (PLL) was developed, in order to improve the recorders robustness against time-base variations.