01-10-2021, 12:42 PM
While some (many?) displays do all sorts of clever things with refresh the fact remains that the input to the display system is a sequence of pixels and lines, starting at the top left. We haven't yet adopted any other model for visual information sent by electronic means. In the route from sender to display we may process the data in many and complex ways but it's still an array of pixels. We could choose to send a frame's worth of pixels in any order we like but by convention we still start at the top left corner. En route we may put pixels in blocks, describe them in the frequency domain (cosine and fourier transforms) or by other transforms (fractal, walsh, hadamard) all in the service of sending as few bits as possible while keeping good pictures.
LCD displays are inherently zero order hold. In other words a pixel stays at its last setting until it is refreshed. Think infinite persistance in a phosphor. This means no large area flicker, regardless of frame rate. This can also give blurry motion. Other displays (plasma, OLED) don't have zero order hold. Hence the portrayal of motion will differ on different types of display. And that's before any interframe processing for data compression.
H and V blanking are now historic artefacts. CRTs and camera tubes needed them, modern displays don't. In a studio context the space isn't wasted, it carries all sorts of data such as timecode and embedded audio. For transmission it's a waste of data so blanking intervals are omitted.
The attached paper shows how 2 BBC research engineers saw the early development of digital TV. Well worth reading. In 1974/5 I spent a gap year (the term hadn't been invented) between school an uni at BBC Research (Kingswood Warren). I met the authors and many of the people mentioned in the article.
LCD displays are inherently zero order hold. In other words a pixel stays at its last setting until it is refreshed. Think infinite persistance in a phosphor. This means no large area flicker, regardless of frame rate. This can also give blurry motion. Other displays (plasma, OLED) don't have zero order hold. Hence the portrayal of motion will differ on different types of display. And that's before any interframe processing for data compression.
H and V blanking are now historic artefacts. CRTs and camera tubes needed them, modern displays don't. In a studio context the space isn't wasted, it carries all sorts of data such as timecode and embedded audio. For transmission it's a waste of data so blanking intervals are omitted.
The attached paper shows how 2 BBC research engineers saw the early development of digital TV. Well worth reading. In 1974/5 I spent a gap year (the term hadn't been invented) between school an uni at BBC Research (Kingswood Warren). I met the authors and many of the people mentioned in the article.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
