Apparatus and method for controlling the capstan motor of the video cassette recorder having function of automatic five/slow playback

A method for controlling automatically a fine-slow movement of a video tape in a VCR, comprising:

• controlling a capstan motor with servo control means using a capstan drive signal, said capstan drive signal active over a slow playback interval commencing with a front and ending with a rear, and said capstan drive signal operative under control of slow control data to control the capstan motor to move the video tape;
• detecting a control pulse from the video tape at a control pulse location between the front and rear of the playback interval and applying the detected control pulse to said servo control means;
• envelope detecting an envelope signal from a radio frequency playback signal from the video tape;
• sampling the detected envelope signal from said envelope detecting means;
• forming sampled first values proportional to the portion of the detected envelope signal between the front of the playback interval and the control pulse location;
• forming a sampled second values proportional to the portion of the detected envelope signal between the control pulse location and the rear of the playback interval;
• A/D-converting the sampled first and second values to form first and second digital values;
• comparing the first digital value with the second digital value to provide a greater-than result or a less-than result;
• providing said slow control data to said servo control means to control said capstan drive signal such that said control pulse location is moved, relative to said front and rear of the playback interval, in one direction in response to said greater-than result and in the opposite direction in response to said less-than result whereby the video tape is tracked over the playback interval.

An apparatus for automatically controlling movement of a video tape in a VCR comprising:

• servo control means for controlling a capstan motor with a capstan drive signal, said capstan drive signal active over a playback interval, said playback interval commencing with a controllable GO pulse in the front and a STOP pulse in the rear, said drive signal for driving the capstan motor to move the video tape;
• control head means for detecting a control pulse from the video tape at a control pulse location between the front and rear of the playback interval;
• envelope detecting means for receiving a radio frequency playback signal from the video tape and detecting an envelope signal from the playback signal;
• and
• a microcomputer for sampling the detected envelope signal from said envelope detecting means, forming sampled first values proportional to the portion of the detected envelope signal between the front of the playback interval and the control pulse location, forming sampled second values proportional to the portion of the detected envelope signal between the control pulse location and the rear of the playback interval, A/D-converting the sampled first and second values to form first and second digital values, comparing the first digital value with the second digital value to provide a result, providing said result to said servo control means to control the time of the GO pulse and the STOP pulse so as to tend to make said first and second digital values equal whereby the video tape is tracked over the playback interval.