Variable-speed regeneration compensating apparatus for double azimuth 4-head type video tape recorder

Claim 1

A double azimuth 4-head type video tape recorder comprising: first and second standard speed regenerating heads oppositely disposed on a revolving drum at an angle of 180 degrees, and having external circumferential surfaces inclinedly facing a strip shaped running recording medium; first and second low speed regenerating heads oppositely disposed at an angle of 180 degrees, and each positioned adjacent to a different one of said first and second standard speed regenerating heads; standard speed regeneration head switching means for generating a selected standard speed regenerating signal by alternatively switching between standard speed regenerating signals of one of said first and second standard speed regenerating heads in dependance upon which one of said first and second standard speed regenerating heads is facing said strip shaped running recording medium in response to a regenerating head switching pulse, said regenerating head switching pulse being in a first state during the interval of 180 degrees of said revolving drum with said first standard speed regenerating head and said second low speed regenerating head facing said strip shaped running recording medium and being in a second state during the interval of 180 degrees of said revolving drum with said second standard speed regenerating head and said first low speed regenerating head facing to said strip shaped running recording medium; low speed regeneration head switching means for generating a selected low speed regenerating signal by selectively switching between low speed regenerating signals of one of said first and second low speed regenerating heads in dependence upon which one of said first and second low speed regenerating heads is facing said strip shaped running recording medium in response to said regenerating head switching pulse; standard speed regeneration envelope detecting means for generating a standard speed regeneration envelope being a detected envelope of said selected standard speed regenerating signal; low speed regeneration envelope detecting means for generating a low speed regeneration envelope signal being a detected envelope of said selected low speed regenerating signal; envelope comparing means for generating a standard speed recorded medium regeneration signal switching pulse being in a first state when said standard speed regeneration envelope is larger than said low speed regeneration envelope signal and being in a second state for compensating for said first state when said standard speed regeneration envelope signal is smaller than said low speed regeneration envelope signal according to comparisons of magnitudes of said standard and low speed regeneration envelope signals; standard speed recorded medium regeneration signal switching means for generating a standard speed recorded medium compensated regenerating signal by selecting and switching a greater one of said standard speed and low speed regenerating signals, in response to said standard speed recorded medium regeneration signal switching pulse of said envelope comparing means during a variable-speed regeneration for a standard recorded mediums; and a low speed recorded medium variable speed regeneration compensating circuit, comprising; first time constant means for supplying a first average of said low speed regeneration envelope signal for said first low speed regenerating head, second time constant means for supplying a second average of said low speed regeneration envelope signal for said second low speed regenerating head, time constant circuit switching means for alternatively supplying said first average and said second average of said first and second time constant means in response to said regeneration head switching pulse during variable speed regeneration of a low speed recorded medium, and low speed recorded medium regeneration signal switching pulse generating means for generating a low speed recorded medium regeneration signal switching pulse when said low speed regeneration envelope signals smaller than first and second reference signals by comparing said first average and said second average supplied by said time constant circuit switching means; wherein said low speed recorded medium regeneration signal switching means switches said low speed regenerating signal to said standard speed regenerating signal to be generated as a low speed recorded medium compensated regenerating signal in response to said low speed recorded medium regeneration signal switching pulse.

Claim 14

A method for performing variable speed reproduction of video signals recorded on a video tape in a four-head video tape recorder, said method comprising: generating first standard speed head signals from said video tape; generating second standard speed head signals from said video tape; generating first low speed head signals from said video tape; generating second low speed head signals from said video tape; alternatively providing said first standard speed head signals and said second standard speed head signals as standard speed regenerating signals in response to regeneration head switching pulses; alternatively providing said first low speed head signals and said second low speed head signals as low speed regenerating signals in response to said regeneration head switching pulses; generating output regeneration signals by alternatively providing one of said standard speed regenerating signals and said low speed regenerating signals in response to signal switching pulses; detecting first envelope signals and second envelope signals of said first low speed head signals and said second low speed head signals, respectively; and generating said signal switching pulses in response to said first envelope signals and said second envelope signals after compensating for average level differences between said first envelope signals and said second envelope signals.

Claim 15

A method for performing variable speed reproduction of video signals recorded on a video tape in a four-head video tape recorder, said method comprising: generating first standard speed head signals from said video tape; generating second standard speed head signals from said video tape; generating first low speed head signals from said video tape; generating second low speed head signals from said video tape; alternatively providing said first standard speed head signals and said second standard speed head signals as standard speed regenerating signals in response to regeneration head switching pulses; alternatively providing said first low speed head signals and said second low speed head signals as low speed regenerating signals in response to said regeneration head switching pulses; generating output regeneration signals by alternatively providing one of said standard speed regenerating signals and said low speed regenerating signals in response to signal switching pulses; detecting first envelope signals and second envelope signals of said first low speed head signals and said second low speed head signals, respectively; and generating said signal switching pulses in response to said first envelope signals and said second envelope signals after compensating for average level differences between said first envelope signals and said second envelope signals.