【 Weak current College 】 video quality rating and category---Power By 【 China power house network 】

According to the different conditions of real-time video transmission requirements, you can set the video quality of service is divided into five levels. Are the high definition television (HDTV) Conference, Studio-quality digital TV, broadcast quality TV and VCR quality TV and video quality.

1.HDTV quality

HDTV definition, standard and HDTV-related technology is nearly 10 years of the HotSpot. For motion picture, people can feel the quality of the two parameters, namely the number per second of Chen (f/s) and the resolution of each image. Therefore measure the HDTV quality of service is usually the combination of the two parameters. Motion video format of two other important parameter is the image-aspect ratio and scanning mode. -Aspect ratio is defined as the width to height-ratio. HDTV 16: 9, current TV is 4: 3. Campaign images there are two ways to scan, interlaced and progressive scan.

2. Studio digital TV quality

20 practical in the mid-1980s, the International Telecommunication Union (ITU) proposed the concept of digital TV, and specifies to digital encoding forms to transfer video TV signal first standard, that is, it is recommended that ITUCCIR601 compatible standard collection instead of a single standard. In addition, standard-rate CCIR-601 per second 30-or 25-per-second, interlaced scanning mode.

3. broadcasts TV quality

Due consideration to the transmission network of residual frequency interference in the transmission of television signals, which characterizes the rate vary, United States of using the NTSC 30HZ-rate (or 60 Hz field frequency). The European PAL or SECAM is used in Zhen rate 25HZ (or 50 Hz field frequency). Besides these two standards used by Zhen-frequency, resulting in the number of rows per-different, because the total bandwidth is restricted, thus NTSC uses Kwang-525 line, PAL or SECAM 625 rows selected.

4.VCR quality

VCR quality refers to a VHS quality video show broadcast quality of programme quality can be observed. The resolution is a PAL or SECAM broadcast quality TV.

5. quality of the video conference

In the IP network application of multimedia communication, due to the consideration of IP network bandwidth limit, current video service quality mainly five quality levels in the worst of a rating. Video conferencing quality characteristics can consist of the following quantitative parameters.

(1) resolution is one quarter of the broadcast quality

Video conferencing has many possible resolution levels, such as ITU-TH. 261 standard used to define the encoding of video conference quality and compression resolution. This format is called common intermediate format (CIF), defines the CIF 352 pixels per line and per-288 lines of resolution. Therefore, each space axis pixel number is half of studio quality, which led to the two-dimensional resolution divided by factor 4.

(2)-spectrum in the 5-25f/s or so

Considering the channel bandwidth of qualified, reduced spatial resolution still is not enough, the drop in frequency must also characterizes. Depending on the complexity of the image, the quality of the video conference-frequency is 5-25f/s.