from Wikipedia
720p (720 lines progressive) is a progressive HD signal format with 720 horizontal lines/1280 columns and an aspect ratio (AR) of 16:9, normally known as widescreen HD (1.78:1). All major HD broadcasting standards (such as SMPTE 292M) include a 720p format, which has a resolution of 1280×720.
The number 720 stands for the 720 horizontal scan lines of image display resolution (also known as 720 pixels of vertical resolution).[1] The p stands for progressive scan, i.e. non-interlaced. When broadcast at 60[note 1] frames per second, 720p features the highest temporal resolution possible under the ATSC and DVB standards. The term assumes a widescreen aspect ratio of 16:9, thus implying a resolution of 1280×720 px (0.9 megapixels).
720i (720 lines interlaced) is an erroneous term found in numerous sources and publications. Typically, it is a typographical error in which the author is referring to the 720p HDTV format. However, in some cases it is incorrectly presented as an actual alternative format to 720p.[3] No proposed or existing broadcast standard permits 720 interlaced lines in a video frame at any frame rate.[4]
Comparison with interlace scanning
[edit]Progressive scanning reduces the need to prevent flicker by anti-aliasing single high contrast horizontal lines.[5][6] It is also easier to perform high-quality 50↔60 Hz conversion and slow-motion clips with progressive video.
Resolutions
[edit]| Standard | Resolution | Aspect ratio |
|---|---|---|
| HD | 960×720p | 4∶3 |
| HD | 720×960p | 3∶4 |
| HD | 1280×720p | 16∶9 |
| HD | 720×1280p | 9∶16 |
Notes
[edit]See also
[edit]
References
[edit]- ^ "720p – AfterDawn: Glossary of technology terms & acronyms".
- ^ Hoffner, Randy (2008-01-09). "Will the End of NTSC Be the End of 59.94?". TVTechnology. Retrieved 2010-10-08.
- ^ Briere, Daniel; Patrick Hurley (2006). HDTV for Dummies. For Dummies. p. 13. ISBN 9780470096734.
- ^ "ATSC Standard: Video System Characteristics of AVC in the ATSC Digital Television System" (PDF). 2008-07-29. Archived from the original (PDF) on 2012-10-04. Retrieved 2011-07-24.
- ^ "720p". AfterDawn. 2010-08-10. Retrieved 2010-10-08.
- ^ "720p". CNET Glossary. Archived from the original on 2010-09-30. Retrieved 2010-10-08.
External links
[edit]from Grokipedia
Overview
Definition
720p is a high-definition television (HDTV) video format defined by 720 active horizontal lines of vertical resolution and progressive scanning, with the "p" in the nomenclature indicating progressive scan.[https://tech.ebu.ch/docs/tech/tech3299.pdf] This standard, also known as 720p/50 or 720p/60 depending on the frame rate region, ensures the entire image is rendered line by line in a single pass per frame.[6] The 720p format uses 1280 pixels horizontally by 720 lines vertically for a 16:9 aspect ratio, resulting in 921,600 total pixels. The term "720" specifically refers to the count of active lines contributing to the visible image height, with the horizontal pixel count fixed at 1280 in standard HDTV implementations.[https://tech.ebu.ch/docs/tech/tech3299.pdf] In video systems, resolution describes the sharpness of an image through the dimensions of horizontal pixels and vertical lines, where vertical resolution is typically measured in the number of scan lines.[https://www.itu.int/itunews/issue/2001/02/hdtv.html] For 720p, this vertical line count of 720 provides a foundational measure of detail, distinct from the full pixel matrix that determines overall clarity.[https://tech.ebu.ch/docs/tech/tech3299.pdf] Within the broader HDTV ecosystem, 720p serves as one of the core formats, commonly alongside 1080i (interlaced scanning at 1080 lines) and 1080p (progressive at 1080 lines), enabling enhanced picture quality over standard-definition television.[https://www.atsc.org/standard/a53-digital-television-standard-part-4-mpeg-2-video-system-characteristics/] It is often implemented with a 16:9 aspect ratio for widescreen viewing.[https://tech.ebu.ch/docs/tech/tech3299.pdf]Key Characteristics
720p employs progressive scanning, where each frame is rendered line by line in a single pass, resulting in smoother motion reproduction compared to interlaced formats.[7] This attribute makes 720p particularly effective for dynamic content, such as sports broadcasts, where rapid movement benefits from reduced artifacts and enhanced clarity during fast-paced scenes.[7] Additionally, its lower bandwidth requirements—typically demanding less data throughput than higher resolutions—facilitate efficient streaming and transmission over constrained networks.[2] This efficiency extends to broad device compatibility, supporting seamless playback on older hardware, entry-level displays, and mobile devices without extensive upscaling needs.[8][2] While 720p offers slightly less visual detail than 1080p due to fewer pixels, this trade-off is often negligible on smaller screens or at typical viewing distances, prioritizing fluidity over sharpness in motion-heavy applications.[7][2] Common frame rates for 720p include 23.98, 24, 25, 29.97, 30, 50, 59.94, and 60 frames per second, varying by region and application, with higher rates like 50 or 60 fps enhancing perceived smoothness by capturing more temporal information, which is ideal for interactive or real-time video.[8][9] In terms of hardware demands, 720p's reduced pixel count lowers processing requirements, contributing to greater energy efficiency in devices like laptops and projectors, where it can extend battery life and minimize heat generation during prolonged use.[10] This makes it a practical choice for resource-limited environments, balancing quality with operational sustainability.[2][10]Technical Specifications
Resolution Parameters
The 720p video format is defined by a standard resolution of 1280 pixels in width by 720 pixels in height, resulting in an active picture area of 1280 × 720 pixels. This configuration adheres to a 16:9 widescreen aspect ratio, where the ratio of width to height is precisely 16/9, ensuring compatibility with modern display devices that utilize square pixels for accurate geometric representation. The most common variant, often denoted as 720p with 1280 × 720 dimensions, serves as the baseline for high-definition content production and broadcast. Standards support additional frame rates including 23.976, 24, 25, 29.97, and 30 frames per second, depending on the application and region.[11][11] Regional variations in frame rates adapt the format to legacy analog standards: 720p60 operates at 60 frames per second (or 59.94 in some NTSC-derived systems), prevalent in North American ATSC broadcasts, while 720p50 uses 50 frames per second for European and PAL-region DVB transmissions. These frame rates do not alter the spatial resolution dimensions but influence temporal aspects, with pixel aspect ratios remaining 1:1 (square pixels) across both to maintain consistent image scaling. The vertical resolution of 720 lines refers to the number of active horizontal lines in each frame.[11][12] The total number of pixels per frame is calculated as 1280 × 720 = 921,600, providing a balance between visual fidelity and resource efficiency compared to higher-resolution formats. This pixel count directly impacts storage and bandwidth requirements; for instance, uncompressed 720p50 in 4:2:2 10-bit color sampling yields a net bit rate of approximately 0.92 Gbit/s, though practical compressed streams (e.g., via MPEG or HEVC) reduce this to 8–15 Mbps for broadcast, facilitating lower storage needs and transmission costs. Pixel density implications arise from this resolution on varying display sizes, where smaller screens achieve higher perceived sharpness due to denser pixel packing, while larger displays may reveal limitations in fine detail without upscaling.[9]Progressive Scanning
Progressive scanning is a video display and transmission technique in which all lines of each frame are captured, stored, and drawn sequentially from top to bottom in a single pass, without dividing the image into alternating fields.[13] This contrasts with interlaced scanning, which alternates between odd-numbered and even-numbered lines across two separate fields to form a complete frame.[9] In the 720p format, progressive scanning operates by refreshing the entire frame in each display cycle, effectively treating each field as a complete image rather than a half-frame.[13] This sequential approach minimizes visual artifacts such as flicker and jagged edges (often called "combing") during motion, as the full vertical resolution is presented consistently per frame, making it particularly suitable for dynamic content like sports broadcasts.[9] A key technical aspect of progressive scanning in 720p is that the field rate directly equals the frame rate, eliminating the temporal offset inherent in interlaced systems.[13] For instance, a 60 fps configuration displays 60 full frames per second; this is denoted in standards like MPEG-2 video encoding by setting the progressive_sequence flag to 1.[13] In interlaced formats, the frame rate is halved relative to the field rate due to the alternation, but progressive scanning avoids this division, yielding Frame rate = Field rate.[13] The bandwidth requirements for 720p progressive video can be approximated using the formula for uncompressed data:
This estimation accounts for the sequential nature of progressive scanning, where the full pixel count is processed at the frame rate without field interleaving; for example, in a 10-bit 4:2:2 color space at 50 fps, the raw bitrate approaches 0.92 Gbit/s as specified in production standards.[9]