eli5; Why do tapes have screen tearing and splitting, but modern media doesn’t?


I get that TVs have faster refresh rates now but even if you play a dvd on an old tv it doesn’t tear when you pause it. What was so different about vhs tapes that made them freeze mid transition? Cause from what I understand, unlike actual film, which would have mid frame pauses, tape is encoded the exact same way as a disk or even a stream, so why do they buffer instead of tear?

In: Technology

VHS tapes were never meant to be able to display an image while paused. That’s because in order to display an image the read head inside the VCR needs to be scanning over the tape and displaying the signal to the TV.

When you pause your VCR there isn’t any tape moving past the read head anymore. Most VCRs hacked together a method of having at least some image on screen by just scanning and rescanning the bit of tape that happened to be under the read head when you paused the video. But, this method is imperfect and leads to the image quality problems that you described.

DVDs store video digitally and there is a concept of an individual frame of video that can be paused and displayed.

The difference is a physical/analog medium versus a digital one. One medium requires reading like the previous answer said. The other is simply a digital file. When you pause a tape, you pause on whatever frame on the tape it has. And maybe caught between two frames. This image is displayed back to the tv… as it read… including all ‘noise’ on the head which shows up as lines and tearing. Digital media doesn’t have that fault. The file is either there or not, and displayed as such. Digital media doesn’t require being read by a a head like in a VCR. In digital media there’s no third party that needs to read the media as it is displayed. It’s just a file, fully digital.

You have to understand tape literally is frame by frame action. Like taking a photo 30 or 60 times in a second and strewing them together to make it look like it’s moving. If you were to flip through those photos and stop mid way. You’d probably catch a piece of the previous photo or frame. Causing your lines and tearing to be seen.

Information on a VHS was an analog signal. To fit all of it on a tape in a linear form would end up with miles of tape. So they record the information in diagonal stripes across the tape, which is much wider than it would need to be if it just held a single track. This is then played back through a spinning head that is place at the same angle relative to the tape as the information on it. The tape moved by the head as the head spins, reading each stripe in a fluid motion, creating the smooth video you see on playback. Pausing it stops the tape moving, but not the spinning head. So the image you see is whatever that spinning head is reading repeated over and over. Hence the stuttery or “between frames” effect.