"IPTV audio and video codec technology"
a situation of tripartite confrontation
At present, in IPTV service, the choice of audio and video coding and decoding technology presents a tripartite situation, namely mpeg4asp, H.264 and AVS. Mpeg4 and H.264 are the standards of relevant international organizations, and AVS is the national standard of China. As an important link in the IPTV industry chain, telecom operators such as China Telecom and China Netcom have similar ideas for the development of audio and video codec technology. They are pushing H.264. At the same time, they show a wait-and-see attitude towards AVS, indicating that IPTV equipment manufacturers may also be required to support AVS in the future.
Compared with H.264 and AVS technical standards, mpeg4asp has the earliest start time and the highest degree of industrialization in the streaming media and IPTV application market. Therefore, it has been most widely supported by IPTV equipment providers at this stage. In addition, another important link in the domestic IPTV industry chain, radio and television departments (content operators) also tend to mpeg4. Among the three, AVS has the lowest degree of industrialization, followed by H.264.
From a market perspective, MPEG2 product technology is the most mature and widely used in the foreign IPTV market. It has also been recognized and widely used in the domestic digital radio and television market. Since Microsoft's vc-1 or wm9 is a foreign manufacturer's standard, it can neither be recognized by the national standardization organization nor strongly supported by domestic operators from the perspective of the development of IPTV industry or digital radio and television industry.
Formulation of standards
First, we need to understand the meaning of various standards in the domestic IPTV industry. At present, the standards in IPTV industry mainly refer to national standards, industrial standards and enterprise standards. National standards are formulated and promulgated by the administrative department in charge of Standardization (National Standardization Management Committee), industrial standards are formulated and promulgated by the competent ministries and commissions, and enterprise standards are formulated by the enterprise itself. National standards and industrial standards can be divided into mandatory standards and recommended standards.
At present, there is no IPTV national standard in the IPTV industry. Relevant departments of the Ministry of information industry are currently formulating IPTV industry standards, which may become IPTV national standards in the future. AVS is a recommended national audio and video codec technical standard, which will be recommended and cited in IPTV industry standards. The IPTV standards formulated by China Netcom and China Telecom belong to IPTV enterprise standards. If the radio and television departments also need to formulate relevant IPTV industry standards, their specifications will also have an important impact on the selection of IPTV audio and video codec technology.
To be exact, the current debate on audio and video codec technology standards in the domestic IPTV industry is mainly reflected in the choice of video codec technology in the IPTV standard, while there is no too much debate and detailed consideration on the choice of audio codec technology in the industry. In IPTV system, video and audio codec technologies are relatively independent. For example, at present, IPTV system equipment from different manufacturers support one or more audio formats in different audio codec technologies such as mpeg1layer2 (MP2), mpeg1layer3 (mp3), mpeg2aac, mpeg4aac, etc.
Foreign or local?
Audio and video codec technology is the key technology of digital audio and video, which is widely used, including digital TV, IPTV, mobile TV, VCD / DVD player, and other digital media terminal equipment. For simple economic reasons, the use of foreign audio and video codec technical standards will not only pay huge patent fees, but also directly affect the whole industrial chain, such as chips, software, front-end equipment, storage, transmission, terminal equipment and so on.
As a standard with independent intellectual property rights in China, AVS can not only enable Chinese enterprises to avoid the trouble of patent fees, but also play a strategic role in protecting and promoting the healthy development of domestic digital audio and video related industries. It is against this background that AVS was officially promulgated as the national audio and video coding standard in February 2006, and after the video part, audio, mobile video, system, digital rights management and other parts will be approved and released one after another. Based on many reasons such as technology, economy, IPTV policy and industrial protection, the selection of audio and video codec technology in the domestic IPTV industry involves not only IPTV equipment providers, telecom operators, content providers and chip providers, but also content operators, the Ministry of information industry and domestic AVS standard organizations.
As the standard setter of IPTV industry, the Ministry of information industry aims to protect the healthy development of the whole domestic industrial chain and promote the best social benefits, and the AVS working group itself has received the key support of the Ministry of information industry. Therefore, it can be predicted that AVS will be the basic choice of audio and video coding technology for IPTV industry standard. At present, AVS is in the process from standardization to industrialization. The codec chip, encoder and set-top box based on AVS have not been produced.
Since the AVS standard has just been promulgated and the commercialization has not yet started on a large scale, it is easy to understand why MPEG4 is more supported by radio and television departments and IPTV equipment providers at this stage. Compared with AVS and H.264, MPEG4 codec equipment and streaming media server are more mature and widely used, and the content stored in MPEG4 format is also more widely. However, although MPEG4 started earlier, the vigorous development of MPEG4 still relies on the launch of the domestic IPTV market to a great extent.
As for H.264, in addition to its advanced technology, another important reason why domestic telecom operators push H.264 is that H.264 has avoided MPEG4's patent fees to operators, that is, the way of H.264's royalty collection has dispelled the shadow of MPEG4 charging which was originally enveloped in the domestic telecom operators. Therefore, even when the cost of H.264 is higher than that of MPEG4, H.264 still makes domestic telecom operators rejoice and rejoice.
In 2002, mpeg-la published the patent fee of MPEG4. In addition to the fixed codec fee, it also charges the content owner and content provider according to the playback time. For domestic IPTV industry, in addition to content operators, IPTV operators also need to pay the relevant patent fees.
This caused an uproar in the industry and directly became an external factor to promote the pace of the H.264 market. However, it is disappointing that in the first half of 2005, the owners of the H.264 patent pool announced the procedures for charging through two authorized agents, mpeg-la and vialcensing, and announced that they would officially charge from January 1, 2006. The purpose of avoiding MPEG4 charging for IPTV operation through H.264 has not been achieved. What is more discouraging is that the existence of the two patent agency organizations also complicates the problem, and may even cause patent users to face the two organizations at the same time, because they represent some patent owners.
Although chip manufacturers already know that H.264 patents are complex and the industrialization process will take some time, they obviously did not expect that operators and terminal manufacturers in the domestic IPTV market are so eager for H.264 technology upgrading, so they are not prepared enough. However, as the upstream of the industrial chain, chip manufacturers are always the first batch of manufacturers to intervene in the field of H.264. Therefore, although they are unwilling that MPEG4 chip will be replaced by H.264 chip before bringing enough profits, they still speed up the development process of H.264 chip.
From the perspective of chip implementation, the efficiency of H.264 is based on the high complexity of its implementation. In terms of its baseline, the complexity of the decoder will be about 3 times that of the H.263 decoder, and the complexity of the encoder will be more than 10 times. In addition, because video processing is a data processing based system, combined with video processing algorithm to realize instruction operand loading and parallel operation will greatly improve the efficiency of data processing.
In H.264, motion estimation adopts multi frame reference technology, which requires the processor architecture to consider the data scheduling mechanism of the processor and the organization of on-chip and off-chip memory. H. Like previous standards, 264 can perform parallel processing based on picture, slice and macroblock level. H. 264 also uses Rd algorithm for mode selection. All modes have no correlation in calculation, that is, they can operate in parallel. To adapt the parallel processing characteristics of H.264 encoder to the implementation of high complexity H.264 algorithm, the processing chip architecture needs to develop from single core architecture with insufficient processing capacity to dual core and multi-core architecture, which will be an effective way to improve the performance of multimedia processing chip in the next few years. However, the software difficulty of multimedia processing chip (such as compiler, operating system task scheduling, etc.) will greatly increase, which will prolong the implementation cycle and product maturity cycle of H.264 chip.
Although the existing IPTV Set-top box using tidm642 processor can support standard definition decoding of H.264, for IPTV value-added services that broadband operators have been looking forward to, such as video phone and other audio and video services that require set-top box coding, the existing multimedia processing chips are limited by performance and can not provide good support, so that such services can not be realized, It brings considerable technical risks to IPTV business. Moreover, at this stage, the cost of set-top boxes supporting H.264 is high, which greatly improves the market investment cost of IPTV service and increases the market risk of IPTV service.
In contrast, mpeg-4asp, since MPEG organization first announced MPEG-4 technology in November 1998, it has been a considerable period of time as the development basis. A large number of technologically mature chips have been born and put into large-scale applications. Most of these chips used in MPEG-4 have been tested for a long time and have good compatibility and stability. In addition to the continuous improvement of technology, the average unit price is also gradually reduced in terms of price. With the support of these chips, broadband operators can carry out similar value-added services as soon as possible.
Because of this, if H.264 cannot be rapidly applied on a large scale in the domestic IPTV market, MPEG4 chip still has the advantage of software and hardware development cost compared with H.264 chip during this period, and H.264 still needs huge cost investment. In addition, chip manufacturers still need time to stabilize and improve the existing H.264 chips. It is the consideration of cost and stability that restricts and affects the large-scale commercial use of H.264.
The market decides the way out
It is predicted that by 2008, China's broadband users will increase to 100 million. If 20% of them become Internet TV users, the number of IPTV users will reach 20 million; If 20% of the current cable TV users become network TV users before 2008, the number of users will reach 20 million; It is estimated that mobile users will exceed 400 million by the end of 2005. If 5% of them become IPTV users before 2008, the number of users will also reach 20 million. On this basis, it is estimated that the total number of IPTV users will reach 60 million by 2008.
Let's take another look at the selection of coding and decoding technology in the domestic traditional radio and television market, which has the greatest impact on the industrialization of audio and video coding and decoding. CCTV digital TV channel uses foreign MPEG-2 standard. The reasons are as follows: first, in order to ensure the fidelity of signal transmission, MPEG-2 has developed for a long time and the technology is relatively mature; The second is for copyright protection, because CCTV wants to introduce a lot of foreign digital TV program content, and the other party agrees with the MPEG-2 encoding and decoding standard, which can better protect its copyright. In addition, more than 1 million cable digital TV users in China also use MPEG-2 standard. If they are replaced with AVS standard, there must be a cost problem of replacing set-top box.
Observe the market situation of audio and video codec technology from the perspective of application. In terms of broadcasting and DVD applications, MPEG2 is still in the mainstream, but in terms of mobile TV, video conference, video surveillance and videophone, H.264 and MPEG4 are widely used. In terms of product application, DVD is the largest application market of codec at present, and the growth power in the next stage is expected to occur in the video application field of mobile terminals, such as watching digital TV with handheld devices, personal media players, etc. in these fields, H.264 will be more widely used than MPEG4.
On the whole, H.264 has been supported by telecom operators and equipment providers. Whether in the Internet or other application fields, H.264 has the status of occupying the mainstream of the future market. For IPTV industry, it is a foregone conclusion that H.264 replaces MPEG4, but the commercial cost of H.264 will still hinder its large-scale application in the short term. For AVS, because it has the advantage of reducing patent fees for domestic enterprises and has the support of the Chinese government, its application in China is worth looking forward to.
From the perspective of development, audio and video coding and decoding technology is always in the process of continuous evolution. Therefore, the problem facing IPTV equipment providers is not which audio and video codec technology to choose, but whether their IPTV system and solutions can be transparent in the media transmission layer, independent of the codec format, and can be quickly and seamlessly upgraded in terms of system scalability to support various codec technologies at present and in the future., Technology Zone
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