Determinants of image clarity and stability in video conferences

When we buy a video conference, the most important thing is to examine the stability of the system and the audio and video quality. What are the parameters of the video conference? First of all, the video quality we talk about is our usual subjective video quality. A view of an image cannot be systemized by a specific number. Therefore, we can only judge the quality of a video conference by subjectively judging the clarity of the video conference image, and the definition of a video conference is determined by many factors. The first and most important thing is the video resolution of the video conference, the other is the video restoration quality of the video conference encoder, and the last image post-processing technology of the video conference. What determines the image clarity and stability of a video conference? 1. Video resolution Video conference resolution is the resolution of the image collected by the video conference video. This parameter occupies a very important role in the definition of video conference. The resolution of video conference can be divided into QCIF (160*120) , CIF (320*240), 720P (1280*720), 1280P (1920*1280) and other resolutions. The higher the resolution, the clearer the image display. The high-definition video conferencing system on the market is also the image The acquisition resolution reaches a high-definition resolution above 720P. But isn't the higher the resolution, the higher the video quality of the video conference? The answer is no. The resolution of a video conference is only the resolution of the image collection, and the video conference system also needs to go through the three links of video encoding, decoding, and post-video processing. Therefore, the higher the video conference resolution is not the same as the higher the video quality of the video conference. It can only be said that the local video quality increases with the increase of the image capture resolution. Figure 1 shows the images at various resolutions. We also have a big misunderstanding about high-definition cameras. Some manufacturers mark their cameras with very high pixels. Everyone thinks that this must be a high-definition resolution. However, when testing, we found that its resolution is only 640*480. This kind of camera is not actually a high-definition camera. The most basic indicator of a high-definition camera is above the 720P resolution. Therefore, the decisive factor for high-definition cameras is the image capture resolution. 2. The restoration quality of video encoding Video encoding quality is also an important indicator that determines the definition of video conferences. For example, the most popular H.264 encoding has higher encoding quality, and the image restoration ability is stronger than the previous MPEG4 restoration ability. After that image is restored by different video codes, the restoration degree of the image is different. We first need to talk about the process of video encoding. Video encoding first obtains the image of the video capture device, then divides the image into several blocks, and then performs digital conversion on the blocks, and achieves the restored image through intra-frame prediction and extra-frame prediction of the block. Therefore, the smaller the image block, the higher the restoration degree of the image. For example, H.264 uses a minimum of 4*4 blocks for block prediction, while MPEG4 and H.263 use minimum 8*8 and 16*16 Predictive restoration of the blocks, so H.264 encoded images are clearer than MPEG4 and H.263 at the same data transfer rate. Therefore, the definition of a video conference is also related to the restoration quality of the video encoding. 3. Video conference image post-processing technology. Finally, the image definition of video conference is also related to image post-processing technology. Different video conference systems have different image post-processing technologies. Some video conferences add image filtering processing to the image. , To restore the image to remove the checkered effect and so on. Some video conferencing software uses image enhancement technology for images to make the images look clearer. The above are the three main aspects that determine the definition of a video conference. The resolution of a video conference is the most critical factor that determines the local video quality. Video coding is the most important factor that determines the restoration performance of a video in the coding and decoding process, and image post-processing technology is the post-processing of image restoration, which also plays an important role in video conferences.