in a video recorder having a drum with opposing dual record heads , successive fields of only the luminance signal are recorded by the heads during successive head rotations through 180 °. the tape is overwrapped around the drum by a certain angle so that the chrominance signal of each preceeding field may be compressed and recorded during each head rotation through the overwrap angle . because the luminance signal is not mixed with the chrominance for recording , the luminance bandwidth may be increased by about 1 megahertz to occupy the frequency band otherwise occupied by the color - under chrominance signal in the prior art . this provides a significant improvement in overall video image resolution .