Reduced blanking

The term reduced blanking is a method of controlling a screen with a smaller blanking interval in order to either get by with a lower clock frequency or to obtain a higher repetition rate.

Technical background

With conventional CRT monitors , the electron beam that generates the image has to be switched off after reaching the end of the line ( line blanking interval ). This is necessary because the electron beam cannot suddenly jump from the end of the line to the beginning of the next line. If it were not switched off, this would lead to errors in the display of the image. The same applies when jumping back from the end of the picture to the beginning of the picture. Depending on the desired resolution and frame rate, certain times must be observed. In liquid crystal displays (LCD), however, there is no longer an electron beam. For this reason, the dark period between drawing one line and drawing the next can be shortened. The data throughput of the interface can be increased by using the no longer available dark time. The shortening of the dark period is called reduced blanking

advantage

This shortening is z. B. used in the digital video interface DVI to be able to transmit higher resolutions with the same bandwidth without having to use a second data channel (dual link).

The Coordinated Video Timings , a  list adopted by the VESA with standardized video signals, contains z. For example, a pixel data rate of 4.15 Gbit / s for the Full HD resolution "1920x1080" with 60 Hz refresh rate, which is too much for a single-link DVI connection that can only transmit 3.72 Gbit / s . With Reduced Blanking, the required pixel data rate is reduced to 3.33 Gbit / s (older version) or 3.20 Gbit / s (newer version, in which the time for the blanking interval has been further reduced), so that the signal can be transmitted via a Single link DVI connection can be transmitted.