Masuo Umemoto

Digital video recording

Through mutual technology transfer between consumer and professional video recorders, the last 20 years has witnessed a rapid evolution from analog to digital recording. Each new digital videotape recorder (VTR) uses different channel coding. This implies that improving the recording density involves the development of new channel-coding schemes together with evolutionary magnetic tapes and heads. As a result, professional digital VTRs offer the best features for video recording. This paper reviews state-of-the-art magnetic recording devices, signal processing techniques for digital recording. It also describes the specifications for home-use digital recorders for current television systems, and discusses disk recording technology in the future. >

Digital Video Recording Techniques Using 1/2 Inch Metal Particle Tape

During the past ten years, rapid progress has been made in development of recording techniques for home use VTR. Nevertheless, a limit has now been reaches to improvement in such functional areas as SN ratio, resolution, and dubbing. It is now expected that digital recording techniques will be introduced into the video field in the future to assure even further development.

High data rate recording for HDTV digital VTR

A metal-particle tape and sputtered amorphous-on-ferrite (SAF) head with a lamination structure are examined at 150 Mb/s. The C/N of 31 dB achieved at this high bit rate ensures a word error rate of less than 5*10/sup -5/. It is shown to be feasible to record at a bit rate of 180 Mb/s (135 kb/cm). Flying AC erase using an SAF head at a frequency lower than half of the bit frequency is effective for this type of high-data-rate recorder. These recording techniques establish the fundamental feasibility of digital video tape recorders for high-definition TV at 1.2 Gb/s. >

On coding and decoding for high-order partial response systems

High-data-rate signal processing for hard disk drives is discussed. A recording channel is equalized as a partial response (PR) (1+D)(1-D/sup 3/), where D is a delay operator. Furthermore, 1/(1+D) pre-coding scheme is used, and the resulting response is given as (1-D/sup 3/), which achieves three-bit interleaving. The working speed of each Viterbi detector in interleaving PR channels is reduced to one third of the original bit-frequency. The performance of the reduced two-state Viterbi detector in the interleaving PR channel is compared with the conventional two-state Viterbi detector of the PR4 system. As a result, the proposed system improves the signal-to-noise ratio by about 3.0 db compared with the baseline PR4 maximum system. Finally, it is shown that the Error Coding (ECC) scheme for the interleaving needs a reversed hierarchy of ECC and channel coding.

Professional HDTV digital recorder

Some of the essential technology for record/playback systems in professional HDTV digital recorders is described. The full bandwidths of 1125/60 HDTV signals (30 MHz for luminance and 15 MHz each for the two color difference signals) were recorded. An 8-8 mapping channel code and integrated detection were used. A special phase locked loop (PLL) to cope with picture search functions was developed. At the high data rate of 148.5 Mb/s per channel and the high linear density of 0.345 mu m per bit, the recorder operates with a word error rate of less than 10/sup -4/. >

Structured set partitions and multilevel concatenated coding for partial response channels

We present a systematic way to construct multilevel concatenated codes for partial response (PR) channels using: (1) a structured set partition (SSP) of multiple channel output sets and (2) a set of conventional block codes with different error correcting capabilities. A lower bound on the minimum squared Euclidean distance of the constructed codes is given. This bound is based on the interset minimal Euclidean distances of the SSP and the minimum Hamming distances of the used block codes. An example of SSP for the extended class 4 partial response channel (EPR4) is presented. Iterative suboptimal decoding, which combines Viterbi detection on the trellis of the PR channel with algebraic error detection/correction, can be applied to the constructed concatenated codes. Truncated versions of the iterative decoding scheme are simulated and compared with each other.

Interleaved maximum likelihood decoding in high-order partial responses for high-speed magnetic recording systems

A high-order partial response (PR) that is generally represented by (1+D)(1-D/sup n/) and provides both high density and high speed in hard disk drive (HDD) signal processing is proposed. By using a pre-coding 1/(1+D), the n-bit interleaving operation for high-speed processing can be used. When n=3, the reduced equalization noise gain is about 4 dB higher than in the conventional PR4 at a channel density of 3.0, and the same squared Euclidean distance as with the PR4ML is attained in a 3-bit interleaving maximum likelihood detector. High-order PR channels for perpendicular recording are also proposed.

1.2 Gbit/s HDTV digital VTR

Abstract Some of the essential features of the record/playback system of a new 1.2 Gbit/s digital VTR are described. The VTR can record the full bandwidth of 1125/60 HDTV signals, namely 30 MHz luminance, and 15 MHz for each of the two color difference signals. As for low error rate recording techniques, a cross-shape multilayered amorphous head, a 5 stage transversal filter, a playback head with a narrow trackwidth and a special PLL to cope with stunt motion are employed. At a high data rate of 148.5 Mbit/s and a high linear density of 0.345 μm per bit, the recorder confirms reliable operation with a word error rate of less than 10 −4 .

An Experimental 648 Mbits/s HDTV Digital VTR

One of the most sought-after improvements in HDTV equipment is better VTR picture quality. A promising way to achieve this is through digital recording, which is free from picture quality degradation in the recording and playback processes.

An error rate improvement of decision feedback equalization by extraordinary level detection

Decision feedback equalization, which uses extraordinary level detection (Ex-DFE), with two feedback loops in parallel, is a detection technique which achieves not only significant error rate improvements but also detecting performance of burst-errors. As extraordinary level detection does not use any constraint on channel codes, Ex-DFE is effective for both runlength limited codes with minimum runlength parameters d=0 and d=1. The simple implementation, which contains no high-accuracy A/D convertor or Viterbi detector, is suggested.