What is the difference between HD and SD?

2020-06-03 14:27:17 hongling

What is the difference between HD and SD?




       The inevitable trend of the development of high-definition has been recognized by the vast majority of enterprises in the security industry, especially in the past one or two years, a large number of large and small enterprises have appeared in China trying to squeeze into the millions of high-definition fields. These enterprises have the original analog camera manufacturers and traditions." "Network camera + video server" manufacturers, DVR background research and development manufacturers, and even non-security enterprises and non-video surveillance manufacturers.


  What is HD?


  High-definition was first proposed in the field of radio and television. The earliest was developed by the American Society of Motion Picture and Television Engineers (SMPTE) and other authoritative organizations to develop relevant standards. The video surveillance field also widely uses broadcast and television standards, and defines "high-definition" as three standards: 720p (1280×720, progressive), 1080i (1920×1080, interlaced), and 1080p (1920×1080, progressive). form. HD is not an easy task for video surveillance. It involves many links of the monitoring system, from the front-end camera to the transmission, and then to the recording storage and display equipment, in order to reach the "high-definition" indicators need to make corresponding adjustments, as long as one link can not meet the requirements, you can not reach the system "HD" requirements.


   Some manufacturers mainly focus on the front-end camera equipment when promoting high-definition. It is true that the high-definition video effect first comes from the collection of high-definition information. Without the front-end high-definition video collection, it is impossible to talk about the back-end high-definition effect. However, it is not enough to only capture high-definition images. These images only make sense if they reach the storage device and the display device through the transmission device.


  Taking transmission equipment as an example, the video cable transmission technology used in the security monitoring system can be roughly divided into several transmission methods such as coaxial baseband transmission, coaxial modulation transmission, optical cable transmission, twisted pair transmission, and IP network transmission. The above transmission methods have their own advantages and disadvantages, but the most commonly used applications are optical cable transmission and coaxial cable transmission. What about these two methods in the HD surveillance system?


  What is SD?


  Standard definition, English is "Standard Definition", is a video format with a physical resolution below 720p. 720p means that the vertical resolution of the video is 720 lines progressive scan. Specifically, it refers to "standard definition" video formats such as VCD, DVD, and TV programs with a resolution of about 400 lines, that is, standard definition. The physical resolution above 720p is called HD, (High Definition in English) referred to as HD. Regarding high-definition standards, there are two internationally recognized ones: the video vertical resolution exceeds 720p or 1080i; the video aspect ratio is 16:9.


   Standard Definition is a video format with a physical resolution below 720p. 720p means that the vertical resolution of the video is 720 lines progressive scan. Specifically, it refers to "standard definition" video formats such as VCD, DVD, and TV programs with a resolution of about 400 lines, that is, standard definition.


720P is a high-level high-definition digital TV format standard formulated by the American Society of Motion Picture and Television Engineers (SMPTE), and the effective display format is: 1280×720. SMPTE (American Society of Motion Picture and Television Engineering) divides the different types of digital high-definition signal digital TV scan lines into 1080P, 1080I, 720P (i is interlace, interlaced, p is progressive, progressive). 720P is a display format that achieves a resolution of 1280×720 under progressive scanning. It is a fusion of digital film imaging technology and computer technology.


  720p format, resolution is 1280×720p/60Hz, line frequency is 45kHz.


   Detailed HD


High-definition equipment: For display devices such as DVD players, camcorders, projectors and monitors, the so-called "high-definition" is generally not just "720P", but refers to "full high-definition", that is, supports 1920*1080 Resolution video output. These devices are usually expensive.


   High-definition format: Due to the huge amount of high-definition video data transmission, a new compression algorithm is required. The current high-definition video formats are: H.264, WMA-HD, MPEG2-TS, MPEG4 and VC-1. Among them, the H.264 format is currently the most popular. Therefore, when you buy a high-definition disc drive or graphics card, you must figure out whether the device supports H.264.   For example, Nvidia's 8400G graphics card does not support H.264, while 8400GS does.


   High-definition movie: The so-called high-definition movie refers to the full high-definition (1920*1080) video file produced in the high-definition video format. For example, Blu-ray DVD video files are compressed in h.264 format. The current HD video playback is usually done through a computer. Due to the complex algorithm of the high-definition video file and the huge amount of calculation, the CPU and the graphics card have relatively high requirements. Under normal circumstances, a computer playing high-definition video must be equipped with a graphics card with built-in hardware HD decoding function, because the complete soft decompression requires too much CPU.


  Full HD: Technically speaking, the overall physical resolution of the full HD display must reach 1920×1080P, that is, the resolution in the horizontal direction should reach 1920 pixels, and the resolution in the vertical direction should reach 1080 scan lines. LCD TVs that comply with the Full HD standard will be labeled or used as a part of the TV design near the panel, with "FULL HD" to indicate that the physical resolution of the display screen meets the full HD standard of 1920×1080P.


At present, there are many LCD TV products on the market that only reach the 1366X768 high-definition standard, but on the manual or the body, we can often see the "full support for 1080P high-definition display" sign, but this is not really able to reach the full high-definition standard, just Said that it can display 1080P images, but the screen has been greatly discounted, this is just a promotional language for the product "gold."


   Difference between HD and SD


   The distinction between "High Definition" and "Standard Definition" comes first from the video effects that can be seen. Due to the difference in image quality and the bandwidth occupied by channel transmission, digital TV signals are divided into HDTV (high definition television), SDTV (standard definition television) and LDTV (ordinary definition television). From the perspective of visual effects, HDTV has the highest specifications, and its image quality can reach or approach the level of 35mm wide screen movies. It requires video content and display devices with a horizontal resolution of more than 1000 lines and a resolution of up to 1920×1080. From the point of view of image quality, since the resolution of high-definition is basically equivalent to 4 times that of traditional analog TV, the picture clarity and color reproduction are far better than traditional TV. The 16:9 widescreen display also brings wider visual enjoyment. From the perspective of audio effects, high-definition TV programs will support Dolby 5.1 channel surround sound, and high-definition movie programs will support Dolby 5.1 TrueHD specifications, which will bring us super shocking listening enjoyment.


  Simply put, the standard resolution of civilian standard definition video is only 720*480. The civilian high-definition 1080i video shooting pixels are 1080*1444 pixels. The sharpness of the two is very different. Only after you have used it can you feel that the high-definition picture is clear. If conditions permit, you can buy a high-definition machine now. If the high-definition tape drive uses the 1080i hdv video format, it can be edited with a 1394 card captured into the computer. Currently, the latest software supports editing, which is no different from standard definition. And if you want to play back high-definition video programs on an ordinary TV, all you need is the high-definition machine's composite video signal interface or s-video output terminal. You can watch your own video. If you want to enjoy high-definition vision, you can choose to use component or hdmi (high definition multimedia) output. In comparison, the latter can provide the best quality video effects. Of course, you can also watch the high-definition video directly in the computer.


   There is still a certain gap between the image quality of standard definition and high definition, but as a civilian user, the collection equipment for personal use can not meet the standard requirements of high definition. High definition collection equipment is still a relatively expensive product for individuals. At present, the price of the general civil capture card is 200-400, and the effect is just fine. The high-definition generally needs more than 3000. If it is not a business need, it still feels more expensive.


  Personal image products are generally carved into DVDs after collection, and enjoy the exchange. The resolution of 500 lines is enough. 800-line high-definition equipment cannot be realized without the corresponding collection and output equipment.