Dynamic magnetic information storage or retrieval – Converting an analog signal to digital form for recording;...
Patent
1984-10-01
1986-08-05
Canney, Vincent P.
Dynamic magnetic information storage or retrieval
Converting an analog signal to digital form for recording;...
360 143, G11B 500, G11B 509, G11B 2702, H04J 306
Patent
active
046046577
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for processing a PCM signal and, more particularly, to an apparatus suitably used in an apparatus for recording/reproducing a PCM audio signal.
BACKGROUND ART
In a PCM recorder for recording/reproducing a PCM audio signal, a few words each comprising 16-bit data are given as one block. A data error detection/correction code such as a CRC and a parity word is added to each block for detection and correction of a read error bit in the reproduction mode. Normal random and burst errors can be corrected to proper data by using an error detection correction code. However, when a great number of errors occur and cannot be corrected, the error positions are detected, and error correction such as interpolation processing and the holding of the previous value is performed. The interpolation is performed by using two data values adjacent to error data.
On the other hand, error data which is neither detected as an error nor corrected is present. Assume a PCM signal is recorded on a recording medium such as a magnetic tape and the recorded PCM signal is erased to record another PCM signal. When the previous PCM signal is not completely erased due to the presence of dust or the like and the partially left previous PCM signal is reproduced, it cannot be detected as an error by an error detection/correction circuit (check circuit). As a result, error correction or compensation will not be performed, and pulse noise (abnormal sound) such as click noise inherent to PCM recording is generated. In a VTR system using a magnetic tape and rotary heads, when the recorded tape is reproduced at a speed (e.g., slow play or fast play) different from that in the recording mode, or mistracking occurs, the rotary head scans across a plurality of tracks. In this case, an error is neither detected nor corrected. Therefore, an abnormal sound caused by pulse noise is produced.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide an apparatus for processing a PCM signal, wherein the above problem is solved, and errors which cannot be detected by only an error detecting code can be detected to prevent noise generation.
In an apparatus for processing a PCM signal according to the present invention, a plurality of PCM data constitute one block data, and a plurality of blocks constitute one segment data. Each block includes a data error detecting code and a segment address representing a location of the block in the segment. The apparatus comprises a detection circuit for detecting a coincidence
on-coincidence of the segment address for each block in one segment, thereby correcting the data in accordance with a non-coincidence detection signal. Error data which cannot be detected by only an error detecting code can thus be detected to prevent pulse noise from being generated. Therefore, high-quality signal processing can be performed.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a plan view showing part of a magnetic tape used as a recording medium in an audio PCM recording/reproducing apparatus according to an embodiment of the present invention;
FIG. 2 shows a format of one-block data recorded in a track of the magnetic tape;
FIG. 3 is a block diagram showing the main part of an error detecting system of the recording/reproducing apparatus of the embodiment;
FIG. 4 is a block diagram of a coincidence detection circuit shown in FIG. 3; and
FIG. 5, consisting of 5A-5F, is a timing chart for explaining the operation of the circuits shown in FIGS. 3 and 4.
BEST MODE OF CARRYING OUT THE INVENTION
An embodiment will be described wherein the present invention is applied to a rotary head type audio PCM recording/reproducing apparatus.
FIG. 1 is a plan view showing part of a magnetic tape 1 used as a recording medium. The magnetic tape is wound around a rotary head drum by an angular interval of about 90.degree.+.alpha.. Tracks 2 are alternately formed by two rotary heads having different azimuth angles so as to record audio PCM signals. A sampled value (one w
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patent: 4234896 (1980-11-01), Onishi et al.
patent: 4309726 (1982-01-01), Tanaka et al.
patent: 4403263 (1983-09-01), Kageyama et al.
patent: 4423441 (1983-12-01), Ozaki
patent: 4466029 (1984-08-01), Tanaka
Fukami Tadashi
Odaka Kentaro
Canney Vincent P.
Eslinger Lewis H.
Sony Corporation
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