1. Field of the Invention
The present invention relates to a system for recording and reproducing a digital audio signal suitable for use, for example, in a digital video tape recorder (D-VTR).
2. Description of the Prior Art
A digital video tape recorder (D-VTR) has been proposed which converts a video signal and audio signal into digital signals and, when necessary, compresses the signals along the time base. The processed video signal and audio signal then are sequentially recorded as digital video data and digital audio data by means of rotary heads helically scanning a magnetic tape along recording tracks angled with respect to the longitudinal direction of the tape. The original signals then may be reproduced from the recording tracks.
In such a D-VTR, the sampling frequency of the audio signal is set for example to 48 kHz in accordance with standards for interfacing with other audio equipment and therefore one field of the video signal using the NTSC system of standards, has a frequency of 60/1.001 (=59.94) Hz. Hence, the number of samples in one field becomes 48 kHz/59.94 Hz=800.8. Note that such number is not an integer.
In practice the number of samples of the audio data recorded in one field period is set to 801 samples for the 1st to 4th fields and is set to 800 samples for the 5th field. Thus, 4004 samples are recorded during every 5-field period with such a period treated as a cyclic set of periods.
To reproduce an audio signal so recorded, the number of samples of the audio data included in each field is identified. A way to record identification flags with digital audio data is proposed for identifying each field having 800 samples and each field having 801 samples. At the time of reproduction, the identification flag is referred to so that the number of output samples of the digital audio data is controlled. A problem with such a reproducing circuit system in a D-VTR, however, is that an error occurring in the identification flag makes the control of the number of output samples of the digital audio data impossible.