4K video resolution is high-definition (HD) video that has four times the resolution of 1080p HD video. There are two standard resolutions for 4K video. The Digital Cinema Initiatives standard for 4K resolution in the film and video production industry is 4096x2160 pixels. The 4K resolution standard for television and monitors is 3840x2160 pixels.
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Basic viewing requirements
4K adaptive bit rate streams require between 10 Mbps and 20 Mbps of bandwidth. Online video streaming service provider Netflix requires an internet connection speed of 25 Mbps or higher to stream 4K content.
To view 4K resolution content, a 4K TV or 4K monitor is required. The UHD Alliance, a coalition of more than 50 technology companies, entertainment studios and consumer electronics manufacturers, announced an ultra HD specification at the 2016 Consumer Electronics Show to support the adoption of 4K resolution video. This specification lists the features that should be included in devices, like televisions and Blu-ray players, to ensure compatibility with other 4K content and hardware.
To receive the specification, devices must offer:
- A resolution of at least 3840x2160 pixels or higher;
- 10-bit color depth, allowing for 1,024 shades of each of the three primary colors: red, green and blue;
- High dynamic range (HDR) for color accuracy;
- A combination of peak brightness and black level that is either more than 1,000 nits peak brightness and less than 0.05 nits black level, or more than 540 nits peak brightness and less than 0.0005 nits black level.
4K resolution standards and upscaling
H.265 is a video compression standard that was approved by the International Telecommunication Union (ITU) in January 2013. H.265, also known as High Efficiency Video Coding, was designed to support HD video with resolutions up to 8K. It incorporates scalable video coding and promises twice the data compression at the same level of quality as its predecessor, H.264, for 30-40% bandwidth reduction.
VP9, a free, open video compression codec developed by Google, was designed to support 4K video streaming with a 50% bandwidth reduction. It first launched on YouTube to support 4K video streaming, and it was officially released in June 2013. Several web browsers, including Google Chrome, Mozilla Firefox and Opera, support VP9. VP9 has not seen the same widespread industry adoption as H.265, however, as it is viewed as less efficient.
Lower resolution images, such as 1080p HD, can be upscaled on 4K TVs and 4K monitors. 4K devices include dedicated hardware, such as a video scaler and image processing algorithms, to increase the pixel count in lower resolution images. Dedicated upscaling boxes that offer more processing power than hardware built into 4K TVs and monitors can also be used to upscale lower resolutions to 4K.
HDR is a specification that expands the range of bright and dark levels shown on a 4K device. It expands color vibrancy and richness to simulate real-world brightness and darkness.
4K resolution vs. ultra HD vs. 1080p
4K and ultra HD are used interchangeably; however, ultra HD resolution can refer to resolutions above 4K. Ultra HD requires a minimum resolution of 3840x2160 pixels, but includes resolutions as high as 8K.
4K resolution renders images at four times the resolution of 1080p (1920x1080 pixels).
Advantages and disadvantages
The advantage of 4K resolution is that it offers better quality images at a higher resolution. The higher resolution can be beneficial in industries that use detailed images, such as manufacturing and healthcare.
The disadvantages of 4K resolution include high bandwidth and storage requirements, which can negatively impact network infrastructure.
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