How can I lower the resolution on a video I recorded?

What is the resolution of VHS?

• Nowadays, with digital media, picture "quality" is defined by primarily two factors: resolution and frame rate. All things being equal, less pixels per frame and less frames per second result in a lower-quality video of smaller file size. However, what about the VHS/analog format? I've never understood the differences between SP, LP, and EP/SLP when it came to recording to VHS. It does not seem like recording in SLP (versus SP) lowered the frame rate or the resolution ... and yet 3x more video could fit on a videotape recording in SLP. Why can you fit more frames on a videotape when recording in SLP ... doesn't make sense to me? Because correct me if I'm wrong, but wasn't the resolution of pretty much ALL analog video the equivalent of the 480i standard definition? Meaning, prior to the introduction of "HD" to the markets, didn't all television broadcast on SDTVs in 480i, and all video recorded on VHS also in 480i (or whatever the "analog" equivalent is called ... like I said, I have no clue when it comes to analog)? In other words, whether recording in SP or SLP on a videotape ... wasn't the resolution always a 480i equivalent and the frame rate constant (unlike with digital)? So what exactly accounted for the difference in video quality? I mean, even if it's analog on a standard definition TV set ... the TV still has to put in PIXELS, correct? So it seems to me terms like "480i" would still apply even in analog, because "pixels" are not exclusive to digital.

• Answer:

  In order to really answer your question, I'd have to go into a lot of detail that would be best provided in a personal conversation, but I'll give you a portion of the concept. As does any other consumer analog video tape format, VHS records video signals in stripes at an angle across the tape. At all three speeds, the relative velocity between each of the two video heads and the tape is about 19 feet per second. At SP, there is a slight space (called a guard band) between any one stripe and the next one on either side of it. This minimizes what is called "crosstalk", a form of interference. At LP and EP/SLP, there are no guard bands. When a tape is recorded at one of these speeds, each previously recorded stripe is partially erased as the head records the one that follows it. This results in reduced resolution and increased noise. In playback, the head picks up signal from the stripes adjacent to the one that is being played, which again causes a reduction in resolution and an increase in noise -- so at the slower speeds, you get two doses of degradation in one! This is why some later models of VHS machines have 19-micron video heads for EP -- they are very narrow so that they pick up the least possible unintended signal. Now you know how to put two to three times as many frames on the same length of tape: Jam them (much) closer together. The ultimate upper limit on the resolution of standard VHS at SP is about 240 lines (a proper explanation of that would take another essay at least as long as this one is going to be, so I won't go into it) and in some cases as low as 170 lines or so at EP (there really isn't a lower limit). This means, essentially, that VHS can provide up to the equivalent of 240i, but that's rare. Usually, it's no more than the equivalent of 200i to 220i. As to pixels, they didn't really exist until digital video displays came along. Yes, colour CRT TV and monitor screens have discrete dots or stripes of red, green, and blue, but they are not the same as pixels. [A monochrome (black-and-white) screen doesn't have such dots; it's uniformly coated with phosphor.] The term pixel is most properly used to describe a system in which each picture element can be individually targeted or addressed, which requires digital technology. Analog formats and systems have no such capability. In an analog video display (specifically, a CRT screen), the electron beam can strike any spot of phosphor and cause it to glow. Making the beam strike exactly where it should is a matter of adjusting the convergence (another subject for a very long essay) to produce the best possible results. >Beta's tape-to-head speed is about 22 feet per second, allowing a slight improvement in video quality. And it is indeed very slight -- in practice, it is virtually unnoticeable, despite what Betaphiles have claimed for decades. Additionally, in Beta, the azimuth angle is different from that of VHS, and there are some significant differences in how the signal is processed during recording and playback. The two formats' HiFi audio are also implemented in vastly different ways. Not only that, but the two formats place the linear audio track on opposite edges of the tape relative to the direction of tape travel. There are various technical publications that describe these matters in much more detail. Some of them can be found in libraries and in stores that sell used books. This is as much as my aching fingers are willing to type for you today.