Table of Contents
1. HDMI is HD, VGA is not.
The three are not equivalent. HDMI and VGA are both signal transmission methods, while HD refers to a video resolution. HDMI supports HD, and VGA also supports. HDMI currently supports up to 1920*1080p HD format. VGA supports various resolutions from 640*480 to up to 2560*1600. However, VGA is extremely vulnerable to interference from other signals, therefore, the HD resolution is a bit weak. To avoid Image interference, the VGA interface can be used below the resolution of 1920*1080p.
2. High HDMI bandwidth and low VGA bandwidth. So HDMI is better than VGA.
HDMI bandwidth is digital signal bandwidth, VGA is analog signal bandwidth, which is the transmission mode of two different technologies. If you want to compare, you can compare it with the same resolution. For example, HD, HDMI requires 2.2GHz bandwidth, while VGA only requires 172MHz bandwidth. However, high bandwidth does not mean that HDMI transmits more video signals, which is only due to different transmission technologies.
3. HDMI signal does not require digital-to-analog conversion, and there is no signal loss; VGA signal requires digital-to-analog conversion, resulting in large signal loss.
Although HDMI does not require digital analog conversion, it still needs digital-to-digital conversion. No matter what kind of conversion process it is and what it is converted into, it is ultimately a description of analog electrical signals. Their relationship is shown in the following figure:
The signal described by the digital signal is composed of points and is incoherent in the change of the signal, while the change of the analog signal is a continuous curve, therefore, analog signals give people a better sense of reality. When digital signals are converted to analog signals, points (sampling points of digital signals) come out directly, the undescribed part will be automatically generated by the conversion program (similar to the anti-aliasing technology of 3D) to form a continuous analog signal waveform. When analog signals are converted to digital signals, continuous analog signals are converted to digital signals describing points, and the signals become incomplete. From this process, the conversion of digital signals to analog signals has enhancement rather than loss, while the conversion of analog signals to digital signals has loss.
However, in the process of VGA transmission, the signal loss of VGA to LVDS driving LCD panel can be ignored, because under the same digital sampling rate at the front and back ends, these lost signals are originally the parts automatically filled by the program (when digital signals are converted into analog signals), not the loss of the original signals of the digital signal source.
VGA, DVI, HDMI features
VGA
VGA(Video Graphics Array) also has a name called D-Sub. It is an analog signal and can only transmit video signals. VGA interface has 15 pins in total and is divided into 3 rows with 5 holes in each row. It is the most widely used interface type on graphics cards, most graphics cards have this interface. It transmits red, green and blue analog signals and synchronous signals (horizontal and vertical signals). When using VGA connection equipment, the cable length should not exceed 10 meters, and pay attention to whether the connector is installed firmly, otherwise it may cause virtual shadow in the image, in addition, VGA can only transmit VGA, which supports displaying 16 colors or 256 gray levels simultaneously at 640 × 480 resolution, and 256 colors simultaneously at 320 × 240 resolution.
Features:
- It is the transmission of analog signals. The higher the resolution of the display, the more blurred the picture will be. Generally, when the resolution of analog signals exceeds 1280 × 1024, obvious errors will occur.
- Because it is analog information, the signal is extremely vulnerable to interference.
- Unable to convey audio.
- Generally, it is about 30 meters without amplifier and converter, and 150 meters with amplifier and amplifier converter.
DVI
DVI is a digital video interface, which is a high-speed technology for transmitting digital signals and does not undergo digital-analog conversion. There are many specifications for DVI interfaces, including DVI-A, DVI-D, and DVI-I. DVI video transmission avoids the digital-to-analog conversion of the sending end (usually the graphics card) and the analog-to-digital conversion of the receiving end (usually the LCD display) during analog video signal transmission, at the same time, the problem of noise interference in the transmission process of analog signals is also avoided, so the image has no loss.
Features:
- Digital signal, avoiding the analog/digital conversion process, the signal has no attenuation, and the color is purer and more realistic.
- Only transmit video signals, not audio signals.
- Supports multiple formats, including 1920*1080 all HD formats.
- The effective transmission distance is only about 5 meters.
HDMI
High Definition Multimedia Interface (HDMI) is a digital video/audio Interface technology, which is a special digital Interface suitable for image transmission, it can transmit audio and audio signals simultaneously with a maximum data transmission speed of 5Gbps. At the same time, there is no need to convert the number of lines/modules or modules/numbers before signal transmission.
Features:
- Can transmit uncompressed audio signals and high-resolution video signals, digital signals, high quality
- Increase the data transmission bandwidth by up to 5Gbps.
- Supports up to 1080p videos.
- The theory is 20m, but a line of good quality is needed, which is generally within 15 m in the actual market.
- Simultaneous transmission of audio, video and copyright protection is very popular in the field of consumer electronics.
- HDMI is an external interface, which has limited ability to improve video resolution and color depth.
- HDMI compatibility is not good.