Signal discriminating device for VTR having expanded dynamic range

A magnetic recording and reproducing apparatus including a recording system operable with a first and a second recording mode converting a luminance signal of a video signal into an FM luminance signal having a first and a second carrier frequency respectively and recording the FM luminance signal on a magnetic recording medium, and a reproducing system reproducing the FM luminance signal recorded on the magnetic recording medium, said apparatus comprising:

• discriminating means disposed in said reproducing system for receiving said FM luminance signal reproduced from said magnetic recording medium and discriminating as to whether said reproduced FM luminance signal was recorded according to said first recording mode or said second recording mode;
• first signal processing means disposed in said reproducing system for processing said reproduced FM luminance signal recorded according to said first recording mode;
• second signal processing means disposed in said reproducing system for processing and FM luminance signal recorded according to said second recording mode;
• and
• control means responsive to an output of said discriminating means to control application of said reproduced FM luminance signal to one of said first and second signal processing means,
• said discriminating means including:
• a peaking circuit for compensating for lowering of a high-band signal gain caused in magnetic recording and reproduction;
• an AGC circuit for automatically adjusting a gain of an output from said peaking circuit;
• a discriminating circuit for receiving an output signal from said AGC circuit so as to obtain a difference between frequency spectra of said signal by use of band-pass filters respectively corresponding to the first and second recording modes, thereby discriminating a mode associated with said FM luminance signal;
• a noise identifying circuit to which an output from said peaking circuit is supplied in a parallel fashion with respect to said AGC circuit so as to detect an amplitude of the supplied signal such that a detected value is compared with a reference voltage source of a voltage equal to an allowance limit of a noise voltage, thereby producing a noise identifying signal to indicate whether or not the input reproduced signal is a noise;
• and
• a latch circuit for receiving as a data input an output from said signal discriminating circuit and as a control input the noise identifying signal from said noise identifying circuit so as to produce an output as a discrimination output of said discriminating means wherein
• when an amplitude of the output signal from said peaking circuit is greater than a threshold value representing the noise allowance limit, said latch circuit releases a latched state thereof and
• when the amplitude of the output signal from said peaking circuit is smaller than the threshold value, said latch circuit latches a previous value thereof.

A signal discriminating device having a discriminating circuit which detects a difference between frequency spectra of input signals so as to classify the input signals in association with at least two different recording modes comprising:

• an automatic gain control (AGC) circuit connected to receive the input signals thereto as an input and to supply an output therefrom to said discriminating circuit;
• an amplitude detecting circuit for detecting an amplitude of said input signal supplied to said signal discriminating device;
• and
• a hold circuit connected to an output from said discriminating circuit for holding a discrimination output therefrom depending on a reference voltage supplied from said amplitude detecting circuit, said reference voltage being equal to a maximum value of noise information, whereby:
• when an amplitude of the input signal supplied to said AGC circuit is greater than a predetermined threshold value, the output from said signal discriminating circuit is delivered as an output from the device;
• and
• when an amplitude of the input signal supplied to said AGC circuit is smaller than the predetermined threshold value, a previous value of the output of said signal discriminating circuit is kept unchanged by said hold circuit and is delivered as the output of the device.