TV technology terms explained
Here are easy to understand explanations for each feature found on modern TVs and their advantages.
Local dimming – it refers to the ability of the screen to completely shut down lighting in a particular area of the picture, bringing bolder shades of black in the area.
OLED technology makes it very easy to do so. Since every pixel can be shut down individually, local dimming is done at the pixel level. LG uses the term pixel dimming on their TVs.
Things are trickier for LED or LCD screens. TVs that feature a side lighting source can’t generate local dimming. Other models that use LEDs or fluorescent tubes beneath the whole surface of the screen can shut down particular areas, but not as prices as an OLED can do.
4K / Ultra HD – refers to native screen resolution measuring 3840 x 2160 pixels. The standard technological term is Ultra HD, while the most common used name is 4K. The 4K resolution is 4 times larger than FullHD (meaning 1920 x 1080 pixels), being twice the size both on with and height.
Furthermore, a 4K TV will better render your pictures and movies (for example those recorded using GoPro Hero cameras or Sony ActionCam) when streaming from USB media or web services.
Upscaling 4K – refers to a video processing technique that allows a TV to stretch a lower resolution picture into 4K resolution. Usually, this is done on 1920 x 1080 media that is converted to 3840 x 2160 pixels.
Upscaling doesn’t mean an artificial resizing but rather an analysis of each frame and choosing the optimum color and intensity for each new pixel by using math algorithms.
UHD Premium Certification
This certification of quality is only awarded by UHD alliance to those high-quality panels that adhere to a number of imposed conditions. UHD Alliance is a group made of the most panel, TV and video producers in order to define quality standards and encourage the switch to Ultra HD television.
The UHD Premium certification means that a particular TV uses a 4K resolution panel (or higher), it is able to process 10-bit depth signals and display at least 90% of the colors found in the P3 standard while also providing a high brightness or sharp black.
HDR is a recently found term translated as High Dynamic Range. It defines the ability of a TV to render pictures with multiple contrast, brightness and color levels. The main difference consists in revealing more details on dark or bright areas of the screen.
HDR movies need to be recorded with special cameras, but the result is closer to what the human eye is able to see. HDR TVs need to be able to support various brightness levels and process colors on at least 10 bits while being certified for this.
HDR10 is a video standard. It’s used on more TVs than HDR and it is preferred by cheaper models. Technically speaking, it uses a 10-bit color depth and Rec.2020 color palette.
Dolby Video is a higher HDR based video standard, usually implemented on high end TVs alongside HDR 10. The main differences compared to HDR10 are the possibility of 12-bit color processing and availability of dynamic metadata (additional info attached to the video sequence).
Color depth reveals the level of precision at which a certain color shade is coded, usually expressed by names such as “10-bit panel) or “12-bit color processing”. To put it in perspective, an 8-bit TV can display 256 different shades of red, green and blue, all possible combinations leading to about 16 million colors.
In case of 10-bit processing, the total number of combinations lead to over a billion colors.
Standard TVs use 8-bit processing and generate around 16 million colors. The human eye can differentiate between more shades, thus HDR TVs use 10-bit processing or even 12-bit processing to display billions of colors and making possible to outline fine details in HDR pictures.
TV supported codecs
HEVC and VP9 are modern codecs for video compression.
HEVC (better known as H.265) offers double the compression ratio of H.265 but its use has been greatly slowed down by the license costs.
VP9 is a video codec developed by Google. Intended initially for Youtube, VP9 is a good alternative to HEVC. VP9 is offered freely by Google and producers opt for it often.
If you are wondering why does this all matters, think about it this way. If you have a HEVC encoded movie on your flash drive, you won’t be able to play it unless your TV supports the codec. Fortunately, most video files are still compressed in MPEG-4 format which is compatible with the majority of TVs.
Unlike HEVC, VP9 and MPEG-4, avi and MKV are not video codecs. These are actually file containers which include video sequences coded in a particular format and the sound also coded in a different format. MKV container also includes one or more subtitle files. Along with the video and audio codec, a TV needs to be able to read the file container in order to fully play the file.
Dolby Atmos is a surround sound technology that removes the standard channel-based sound distribution (such as 5.1). Instead, Atmos uses sound generating objects and describing their behavior in each frame.
For example, a helicopter is an object which moves from left to right over 5 seconds. Dolby Atoms compatible TVs will know on which side to stream the sound during the scene.
The technology was initially designed for cinema environments but it is also used on premium TVs.
Dolby Digital and DTS are audio codecs that are used with the channel-based sound systems. A 5.1 sound movie includes multiple audio streams, one for each channel (left, right, middle, rear left, rear right and a subwoofer for low frequencies).