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About the difference between VGA, DVI, HDMI

Issuing time:2019-11-10 10:16Author:zonda

About the difference between VGA, DVI, HDMI


Currently in HD devices, the main interfaces are DVI, HDMI, and VGA. Many people have been misled by some intentional or unintentional techniques, and some technical misunderstandings have arisen on these interfaces. So what is the difference between these three interfaces? Put aside your misunderstanding and correctly understand DVI, HDMI, VGA.


First, some misunderstandings about VGA, DVI, HDMI


Misunderstanding 1: HDMI is HD, VGA is not.

These three are not equivalent, HDMI and VGA are both signal transmission methods, and HD refers to a video resolution. HDMI supports HD, and VGA also supports it. HDMI currently supports up to 1920*1080P HD format. VGA supports various resolutions from 640*480 up to 2560*1600, but VGA is very susceptible to interference from other signals, so HD resolution is a bit virtual, in order to avoid picture Interference, below 1920*1080P resolution, you can use the VGA interface.


Misunderstanding 2: HDMI bandwidth is high, VGA bandwidth is low. So HDMI is better than VGA.

The bandwidth of HDMI is the digital signal bandwidth, and VGA is the analog signal bandwidth, which is the transmission method of two different technologies. If you want to compare, you can compare the same resolution, such as high-definition, HDMI requires 2.2GHz bandwidth, and VGA only needs 172MHz bandwidth. But high bandwidth does not mean that HDMI transmits more video signals, just because of the difference in transmission technology.


Misunderstanding 3: HDMI signal does not require digital-to-analog conversion, no signal loss; VGA signal requires digital-to-analog conversion, and signal loss is large.

Although HDMI does not require digital analog conversion, it still has to undergo digital to digital conversion. No matter what kind of conversion process it is, what it is converted into is a description of the analog electrical signal. Their relationship is as follows:


The signal described by the digital signal is composed of one point, which is inconsistent in the change of the signal, and the change of the analog signal is a continuous curve, so the simulated signal gives a better sense of reality. When a digital signal is converted to an analog signal, the direct output is also a point (the sampling point of the digital signal), and the undescribed part is automatically generated by the conversion program (similar to 3D anti-aliasing technology) to form a continuous Analog signal waveform. When an analog signal is converted to a digital signal, the continuous analog signal is converted into a digital signal describing a point, and the signal becomes incomplete. From this process, the conversion of digital signals to analog signals is enhanced rather than lossy, and analog signals are converted to digital signals with loss.

In the VGA transmission process, the signal loss of the VGA to LVDS driving LCD panel can be neglected, because in the case of the same digital sampling rate at the front and rear ends, these lost signals are originally (when the digital signal is converted into an analog signal) the program automatically The part that is filled is not the loss of the original signal of the digital signal source.


VGA

VGA (Video Graphics Array) also has a name called D-Sub. It is an analog signal and can only transmit video signals. The VGA interface has a total of 15 pins, divided into 3 rows and 5 holes per row. It is the most widely used interface type on the graphics card. Most graphics cards have such interfaces. It transmits red, green, and blue analog signals as well as sync signals (horizontal and vertical signals). Use VGA connection device, the cable length should not exceed 10 meters, and pay attention to whether the connector is installed firmly, otherwise it may cause ghosting in the image, and VGA can only transmit

VGA supports simultaneous display of 16 colors or 256 shades of gray at a higher resolution of 640 x 480, while simultaneously displaying 256 colors at 320 x 240 resolution.


Features:

1. It is the transmission of analog signals. The higher the resolution of the display, the more blurred the picture will be. Generally, the analog signal will have obvious error when it exceeds 1280×1024 resolution.

2. Because it is analog information, the signal is extremely susceptible to interference.

3. Can't communicate audio.

4, generally do not add amplifiers and converters in about 30 meters, plus amplifiers and amplifiers can be up to 150 meters.


DVI

DVI is a digital video interface, which is a technology for transmitting digital signals at high speed, and is no longer digital-to-analog. There are various specifications for the DVI interface. Common ones are DVI-A, DVI-D, and DVI-I. DVI video transmission avoids the analog-to-digital conversion process of the transmitting end (usually the graphics card) and the analog-to-digital conversion process of the receiving end (usually the LCD display) during the transmission of the analog video signal, and also avoids the noise interference during the analog signal transmission. Problem, so the image is not lost.


Features:

1, digital signal, avoiding the analog-to-digital conversion process, the signal is not attenuated, the color is more

Pure and lifelike.

2. Only the video signal is transmitted, and the audio signal is not transmitted.

3, support a variety of formats, including 1920 * 1080 all HD formats.

4. The effective transmission distance is only about 5 meters.


HDMI

High Definition Multimedia Interface (HDMI) is a digital video/audio interface technology. It is a dedicated digital interface suitable for image transmission. It can transmit audio and video signals at the same time. The maximum data transmission speed is 5Gbps. . There is no need to perform digital/analog or analog/digital conversion before signal transmission.

Features:

1, can transmit uncompressed audio signals and high-resolution video signals, digital signals, high quality.

2. Improve data transmission bandwidth up to 5Gbps.

3, can support 1080P video.

4, the theory of 20m, but the need for good quality lines, the actual market is generally within 15 meters.

5. Simultaneous transmission of audio, video, and copyright protection is very popular in the consumer electronics field.

6. HDMI is an external interface that has limited ability to enhance the resolution and color depth of video.

7, HDMI compatibility is not good.


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