What is SVHS video?

Like VHS, the S-VHS format uses a "color under" modulation scheme. S-VHS improves VHS's luminance resolution by boosting the frequency deviation of the luminance carrier. This produces a 60% improvement in (luminance) picture detail, or a horizontal resolution of 400 lines per picture height (versus VHS's 240 lines). The often quoted horizontal resolution of 400 means S-VHS captures greater picture detail than even analog (NTSC) cable broadcast TV, which is limited to about 330 lines. In practice, when timeshifting TV programs on S-VHS equipment, the improvement over VHS is indeed quite noticeable. Yet, the trained eye can easily spot the difference between live broadcast TV and a S-VHS recording of it. This is explained by S-VHS's failure to improve other key aspects of the video signal, especially the chroma signal. In VHS, the chroma carrier is both severely bandlimited and rather noisy, a limitation that S-VHS does not address. To be fair, poor color resolution was a deficiency shared by S-VHS's contemporaries (Hi8, Laserdisc, ED-Beta.)