Why Do Video Resolutions Follow Jumps of 144, 240, 360, 480, 720, 1080, 1440, 4000, and 8000?
The common video resolutions such as 144p, 240p, 360p, 480p, 720p, 1080p, 1440p, 4K, 4000p, and 8K 8000p largely follow a pattern based on the vertical pixel count, which is often a multiple of a base resolution. This article explores the historical context, technical reasons, and consumer adoption that led to these specific resolutions.
Historical Context
The historical context of video resolutions begins with the advent of analog television. Standard definition (SD) television formats such as NTSC (525 total scan lines) and PAL (625 total scan lines) were designed with fixed vertical line counts. However, the horizontal resolution was not fixed and could vary based on the bandwidth and device capability. For example, the NTSC standard yielded 480 lines of usable space, while PAL had 576 lines.
When digital devices began to be developed, they often could not handle the full resolution required, so half or quarter sizes were used. This resulted in picture sizes of 240 or 120 vertical lines for NTSC and 288 or 144 vertical lines for PAL. The aspect ratios were also varied, mostly due to the 4:3 ratio of standard TV and film.
Standard TV and Older Film
Standard TV and older film uses a 4:3 ratio, which influenced the pixel aspect ratio. In digital formats, pixels could be square or rectangular, but the chosen values for digital TV and PCs were based on compatibility. For instance, digital NTSC adopted 72480 with square pixels, while PAL used 72576.
Advent of High Definition (HD)
With the advent of high definition (HD) television, the idea of maintaining two separate standards (NTSC and PAL) was less favored. This led to the adoption of two digital resolutions: 720p (720 horizontal lines) and 1080p (1080 horizontal lines). Both were multiples of a fraction of the SD standards, which simplified the process of upscaling standard definition to HD.
Upcoming Resolutions in Digital Era
With HD standards established, room was left for further improvements. The 4K standard (4096x2160) is double that of 1080p, while the 8K standard (7684320) doubles 4K. Note that there is no 4000 or 8000 standard; 4K and 8K refer to the horizontal resolution needed for a 16:9 aspect ratio with these vertical resolutions. For example, 1080p has a horizontal resolution of 1920 pixels, 4K has 3840 pixels, and 8K has 7680 pixels.
They could have been called 2160 UHD and 4320 UHD but are usually marketed by the shorter names 4K and 8K.
Half and Quarter Resolutions
Half and quarter SD sizes were used by digital file formats to save space. For example, 360p is half of 720p, and even though 540p is a possibility, it never gained much use. Modern digital TV and video formats may not always use the wide range of file shapes and resolutions, but picking standard sizes improves efficiency when resizing video for different displays.
Modern Monitor Resolutions
Computer monitors are not restricted to TV standards and can have resolutions like 1366x768 (commonly used in 720p HD TVs) and 2561440 (double 720p resolution and popular for computers). These resolutions represent an intermediate step between 1080p HDMI and 2160p 4K.
Conclusion
As TV standards developed, certain resolutions were adopted for use worldwide. These choices carried over into the digital TV era, ensuring that older video formats remain watchable on new TVs. Understanding the historical, technical, and consumer factors behind these resolutions helps explain why video content follows these specific jumps in pixel counts.
Keywords: video resolution, digital TV, upscaling