Brief Analysis: Four Standards for Video Surveillance HD Image Coding

The most commonly used encoding formats for high-definition video encoding are the four algorithms MPEG2-TS, MPEG4, H.264 and VC-1.

MPEG2 was developed by the MPEG (Moving Picture Experts Group), a working group established by the International Organization for Standardization (ISO) in 1988 to develop standards for motion compression coding. The standards developed are international standards. DVD is MPEG2 encoding, and with the improvement of technology, it has also been applied to high-definition video. The biggest disadvantage of MPEG2 is that the file size is too large, but it also has an advantage, that is, compared with the other two encodings, it consumes the least system resources. However, with the development of hardware technology, the decoding of H.264 and VC-1 will inevitably become like DVD, and any mainstream configuration can play smoothly.

MPEG4 is mainly used for low-bandwidth applications and interactive graphics applications (synthetic content such as games) and interactive multimedia (content distribution and access technology such as WWW). The MPEG expert group established the MPEG4 working group to promote the integration of the above three areas. In early 1999, MPEG4 (first edition) that defined the standard framework became an international standard (ISO/IEC14496-1), and the second edition that provided a variety of algorithms and tools became an international standard (ISO/IEC14496-2) at the end of 1999.

H.264 is perhaps the most promising one. Compared with MPEG2 and MPEG4, its compression efficiency is the highest among the three encodings. The H.264 standard is jointly researched and released by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC). Therefore, H.264 has two names, one is "H.264" using the H.26x name of the ITU-T organization, and the other is AVC (Advanced Video Coding). The biggest feature of the H.264 format is that it can control the file size to one-half or even one-third of the MPEG2 format while ensuring the picture quality. Therefore, its higher compression ratio and better adaptability to IP and wireless network channels are increasingly widely used in the field of digital video communication and storage. However, it should be noted that the price of H.264's superior performance is the increase in computational complexity, so H.264 has the highest hardware requirements.

Microsoft proposed the VC-1 encoding format (codenamed Corona) in September 2003, which has been adopted by many companies such as Movie eam and Modeo. It is also included in HDDVD and Blu-ray. Film companies including Warner and Universal also intend to adopt this format. VC-1 is based on Microsoft Windows Media Video9 (WMV9) format, and WMV9 format has now become the actual implementation part of the VC-1 standard. VC-1 is the last recognized high-definition encoding format. Because it has Microsoft's background, this encoding format cannot be underestimated. Compared with MPEG2, VC-1 has a higher compression ratio; but compared with H.264, the encoding and decoding calculations are slightly smaller.

AVS is a standard built based on my country's independent innovation technology and international open technology. It is mainly aimed at high-definition and high-quality digital TV broadcasting, network TV, digital storage media and other related applications. It has the characteristics of high performance (equivalent to H.264), low complexity (the algorithm complexity is significantly lower than H.264), my country's mastery of major intellectual property rights, simple patent licensing model and low cost. Based on this, it can be considered that the AVS standard is an important standard that can support the development of the country's digital audio and video industry, and is also an important standard that the security monitoring industry should adopt.

JPEG2000 is an image encoding format, not a video encoding format. It was originally designed to replace JPEG, and each frame of a video sequence is equivalent to an image. Compared with its predecessor JPEG, JPEG2000 abandons the block encoding method based on discrete cosine transform DCT, and instead adopts a multi-resolution encoding method based on wavelet transform. The compression rate is about 30% higher than that of JPEG. At the same time, JPEG2000 supports lossy and lossless compression. JPEG2000 has several important features, supporting "progressive transmission" and "region of interest coding". In terms of clarity, it can first decode a quarter of the size of a picture, then half, and finally decode the entire picture; in terms of image quality, it can first transmit the outline of the image, and then gradually transmit data, continuously improving the image quality, so that the image can be displayed from hazy to clear; "Region of interest" means that users can arbitrarily specify the compression quality of the region of interest on the image, and can also choose to decompress the specified part first, so as to highlight the key points. However, JPEG2000 requires too much computation and has a low compression rate. It is currently difficult to implement in embedded real-time systems and also places high demands on storage and transmission. Currently, only some high-definition dedicated systems use this algorithm.

Generally, there are DSP, ASIC and other options for encoding chips. DSP solutions, such as the Da Vinci digital media processor TMS320DM6467, are DSP-based SOCs (systems on chips) that integrate a 300MHz ARM core and a 600MHz DSP core, and use a high-definition video coprocessor. They perform well in executing H.264HP (1080p30fps, 1080i60fps, 720p60fps) synchronous multi-format high-definition encoding, decoding and transcoding. There is also a high-definition entry-level TI chip DM355, which has built-in codec algorithm implementation and can provide high-definition MPEG4SP encoding and decoding capabilities in 720p format and 30 frames per second. It is a good choice for rapid development of entry-level high-definition encoding products. ASIC solutions, such as the HiSilicon 3511 processor, a high-performance communication media processor based on the ARM9 processor core and video hardware acceleration engine, has the advantages of high integration, programmability, and support for multiple protocols such as H.264 and MJPEG (MotionJPEG is a video compression format in which each frame of the image is encoded using JPEG). It can be widely used in real-time video communication, digital image monitoring, network cameras and other fields.