Chojuro Yamamitsu

An experimental study for a home-use digital VTR

An experimental digital VTR system is described. A modified DCT (discrete cosine transform) has been developed for this system that needs only one-half the number of multipliers of a conventional DCT, making the hardware scale smaller. A data quantity estimator controls the variable-length coding for completion within a synchronization block, keeping the picture quality high. Three stages of error correction correct more errors and make the probability of miscorrection lower. A high area packing density of 270 Mb/in/sup 2/ is brought about by the use of a low-noise head amplifier, optimized payback signal processing, high-performance magnetic heads and tapes, and a stable tracking to narrow tracks. >

A Study On Trick Plays For Digital VCR

Approaches to improving the picture quality in high speed play while keeping sufficient picture quality in normal play are described. According to the approaches considered, variable length coding is controlled to be completed within a synchronized block. Each compression block is constructed of DCT (discrete cosine transform) blocks, which separate each other on the screen. The DCT blocks which are in the adjacent synchronized block on the tape are in the adjacent position on the screen. Lower-frequency components are located in the first half of the synchronized block. Computer simulation concerning an evaluation of reproduced picture quality in high-speed play showed that the best method of coding for high-speed play is to form a compression block with DCT blocks adjacent on the screen. >

An experimental digital VCR for consumer use

An experimental digital VCR (DVCR hereinafter) was developed. The DVCR has two new technologies for reduction of tape consumption. One is a bit rate reduction technology of a component video signal down to around 25 Mbps and the other is a high density recording technology. The bit rate reduction technology is based on an 8/spl times/8/2/spl times/4/spl times/8 two dimensional DCT (Discrete Cosine Transform) and a VLC (Variable Length Coding) that completes over 5 macro blocks. Editing, trick plays and invisible error concealments also have been realized by this bit rate reduction while keeping the playback picture quality very high. The high density recording technology is based on ME tape and an ATF (Automatic Track Finding) system. A track pitch of 10 /spl mu/m and a bit length on tape of 0.25 /spl mu/m have been realized. The possibility of a higher linear recording density has been confirmed through theoretical analysis, simulations and experiments. >

An experimental study on bit rate reduction and high density recording for a home-use digital VTR

A description is given of a prototype home digital videotape recorder (DVTR) used for experimentally studying the problems of bit rate reduction while providing high density recording. The authors report on a system adopted that combines two bit rate reducing methods: interfield sub Nyquist sampling and the Hadamard transformation with vector quantization of the resulting joint energy distribution. Using several approaches to high density recording, the prototype system achieved an area packing density of 135 Mb/in./sup 2/ and a linear packing density of 109 Kb/in. at a tape speed of 3.75 m/s. This system is currently capable of one hour recording/reproducing and the feasibilities of two hour recording/reproducing with an area packing density of 270 Mb/in./sup 2/, a linear packing density of 109 kb/in. and a track pitch of 10.3 mu m, were experimentally confirmed by using the same experimental DVTR. >

An Experimental Digital VTR Capable of 12-Hour Recording

Digital VTR which records video-signals digitally is superior to general home-use VTRs with respect to SN ratio, resolution, and dubbing. However, digital VTR or DVTR has demerits, the biggest of which is a huge amount of tape consumption. In particular this demerit is fatal to home-use digital VTRs. Therefore, it is very important to establish techniques which make it possible to record digital video signals as long as possible without excessive tape consumption.

A Two Dimensional Adaptive Digital Decoder for Color Television Signals

Two dimensional adaptive digital decoder has been developed. This decoder samples NTSC signal using burst locked sampling clock whose frequency is 4Fsc. Also the decoder separates the NTSC signal into luminance and two color difference signals using the newly developed 2D adaptive Y/C separation.

A study on high efficiency coding of HDTV at 50 Mbps

High-efficiency techniques for encoding HDTV signals at 50 Mb/s are proposed. An adaptive chrominance interpolation method and an adaptive chrominance decimation method are discussed. It is shown that the distortion of decimation can be decreased and visible distortion can be reduced. Some pictures using these schemes were encoded by computer simulation, and it was confirmed that the processed pictures are adequate for consumer use. >

Variable Speed Search Technique for Digital VCRs

This paper describes a method to permit a videocassette recorder (VCR) to search play at variable speeds (picture in shuttle), in both forward and reverse directions of interframe coded (MPEG-like) signals. Also discussed is a new trick play technique for interframe coded HD-VCR data. This technique is based on analysis of required picture quality and involves special positioning of the data for the trick play mode. Its basic criterion is that picture quality that is inversely proportional to tape speed (lower quality at higher speed) is acceptable to viewers.

A bit-rate reduction for MUSE signal

A novel bit-rate reduction method developed for the MUSE (multiple subNyquist sampling encoding) signal is discussed. This method uses an orthogonal transformation by which the MUSE data-rate is reduced from 1/2 to 1/3 of the original, maintaining a picture quality acceptable for the home-use digital VTR of a HDTV (high-definition television) system. By simultaneous application of two-dimensional DCT (discrete cosine transform) and nonlinear quantization methods for a quincuncial pixel arrangement formed within a field, an optimum data assignment between DCT coefficients and nonlinear quantization values is accomplished by using a variable length coding method. >

Path Feedback Viterbi Detection Without Open Eye Patterns

I.Introduction Ordinarily in digital signal detection, whether in transmission systems or in magnetic recording systems, an equalizer circuit is used to make the eye pattern open, after which digital values are discriminated. But in digital VTRs and other magnetic recording systems with extremely high recording densities, intersymbol interference in playback waveforms is considerable, and equalizer circuits meant to correct such distortion must have strong high-frequency band emphasis characteristics. It has been pointed out that such high-frequency band emphasis induces degradation of the S/N ratio, leading to increases in error rates [1]. In response, equalization methods have been devised which positively