Modulation noise in the roproducing process of a VTR may influence the error rate. We analyzed influence of modulation noise in reproduced digital signals by a theory and experiments. It was found that influence of modulation noise is especially large on signals in high frequency regions. We proposed a new method which can correct errors by using the characteristic of modulation noise. We applied this method to a video tape system, and confirmed the proposed method can correct errors.

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This paper proposes a modulation method suitable for high data density recording for a magneto optical disk. It aims at both high density ratio and DC component suppression. It's said that it's difficult to attain their aims when we use a modulation method including DC component suppression because they have a close relationship. But to do a RLL comding and a DC component suppression separately enables us to achieve them. We developed an 8-15 channel coding minimum length transition was wider to increase density ratio, while we developed an DC suppression method which decided the changing way of modulations based on combination of data and channel code to minimize DC. We also make sure of the effectiveness of the proposed method used both of them.

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An application of the ISI canceller to the PRML (Partial Response Maximum-Likelihood) channels with nonlinear bit shift in high-density digital magnetic recording is studied. The bit-error rate performance is evaluated by computer simulation and the required SNR at the reading point to achieve a given bit-error rate is compared with that of conventional PRML system. It is shown that our system exhibits better performance than conventional PRML system at high recording density.

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We developed the Codec which is able to compress HDTV image data and the encoded data is recorded on the NTSC digital VCR. The source video are made of component signal : luminance Y and color differences Pb and Pr, as defined in the 1125/60 HDTV Studio Standard (BTA S-001). We used subband coding and huffman coding to compress the HDTV signal. Instead of raster scan, we designed the unique cubic scan during 4 frames. The analysis Bank is 3-level tree structured four-channel filter bank. The signal is split into 10 subbands by means of the analysis Bank. We verified recording and playback of HDTV video signal by the Codec.

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We have developed Professional Digital Video Disc Recorder by a stable and high quality digital servo. It is also realized to record digital compressed NTSC signal on both side of φ300PCR (Phase Change Rewritable) disc by using MCAV (Modified Constant Angle Velocity). It's recording rate is 40 Mbps. Therefore we can record a moving picture for 45 minutes.

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The optical disk drive which is installed on satellite or one connected to the communication network has to store large size high speed data such as image data. Plural number of optical disks, therefore, are provided in the drive and data is deployed among those disks. There are various signal source whose word-length is different from each other in such system. When there is a defect on the recording media data error in the playback data is corrected by error correcting code. However, if the defect is too large for correction, error is compensated. This paper describes about error compensation for various word-length. It was shown that when recording block size is large, compensation error noise is small.

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