1.  Technical Field
The invention relates to consumer video cassette recorders (VCR's).  Typically, a VCR includes a tuner capable of selecting one television channel for recording.  When two television channels must be recorded simultaneously, two VCR's may be employed. 
2.  Description of Related Art
There are a number of well-known techniques for dual channel simultaneous video recording.  The most obvious method is to employ straight-forward multiplexing of two video signals into a single channel prior to recording, as exemplified in U.S. Pat.  No.  3,811,008, U.S. Pat.  No.  3,686,434 and U.S. Pat.  No.  3,996,672.  Another technique is to skip-field record each of two video channels simultaneously, interleaving the fields of the two channels, as disclosed in U.S. Pat.  No.  4,139,868, U.S. Pat.  No.  4,027,333 and U.S. Pat.  No.  3,991,266.  Other techniques for handling a plurality of video signals include mixing, as disclosed in U.S. Pat.  No.  4,015,080 and U.S. Pat.  No.  4,001,499.  Video scan conversion is disclosed in U.S. Pat.  No.  3,493,677. 
Problem
In summary, the prior art teaches the addition of circuitry for multiplexing, mixing or field-skipping whenever more than one video signal must be recorded at any one time.  The disadvantage is that such techniques reduce playback image quality and the additional circuitry represents additional cost and complexity.  The problem is a need for a video cassette recorder capable of simultaneous dual channel recording without requiring additional multiplexing circuitry or the like.  Such a video cassette recorder must be capable of simultaneously recording two video channels annd playing back either one of the two recorded channels selectively.