Hardware-based video conferencing products basically follow the basic framework of H.323. The H.323 standard is a standard for video multimedia conference communication based on packet-switched networks defined by the ITU organization. Now widely used LANs and WANs belong to packet-switched networks. At the same time, the standard also takes into account the traditional PSTN call process and the characteristics of IP networks. H.323 covers a series of standards. For example, the network is a packet-switched network with no QoS guarantee based on packet switching, but it can be connected to the H.320 system based on ISDN through a gateway, and to H.324 terminals with low bit rates Wait.
Audio codec standards are G.711, G.723, G.729, etc., video codec standards are H.261 or H.263, data transmission standard is T.120, media stream communication control protocol H.245, call control Signaling H.225, etc. The H.323 standard defines several components for real-time media transmission: terminals, gateways, gatekeepers, and multipoint control units. Hardware products often combine part or parts of several functional modules into one hardware product. For example, MCU can be a single hardware product, but it is also often made into a hardware product with gateways and gatekeepers according to user needs, and even some user terminals have embedded MCU parts.
Most software-only video conference system products are developed based on IP networks according to their own architecture. This software system is basically composed of three parts: Client, Server and network transmission according to C / S or C / W mode. Some of the software products implement some of its modules according to the H.323 standard, such as gateway, MCU, and Gatekeeper software. In recent years, software-implemented video conferencing systems have appeared on the market more and more. The software video conferencing products on the market include Nanjing Tengshang, Weisu, Dongda Qinhuangdao Software ’s Vmeeting system, and Shanda Lianrun video conferencing system. As well as ACMeeting of Longsoft Foundation, the following is a comparison of software-based video conferencing systems and hardware-based video conferencing systems.
In terms of video, hardware-based video conferencing systems, such as H.320 products, are built on a dedicated network such as DDN, ISDN, ATM, etc. This network itself provides good audio and video transmission conditions, so the hardware Video conference products can provide high-quality video images, such as Polycom's ViewStation512 system, which can reach 30 frames per second (NTSC) or 25 frames per second (PAL) at 384 / 512Kbps, and the image resolution can reach 352 × 288, The image has no jitter and delay. Most software video conferencing products are built on IP networks, and the effects are somewhat different from those of hardware products. However, with the improvement of network bandwidth and the guarantee of QoS, the video effects are gradually improving.
In terms of audio, because audio data does not have high bandwidth requirements, both hardware and software-based video conferencing products can achieve better compression effects without distortion of speech.
In order to achieve the video image effect corresponding to its price, the products implemented by the network adaptive hardware often have strict bandwidth requirements. The typical access methods are dedicated networks such as ISDN, DDN, and Frame Relay, which have high requirements for IP networks and minimum bandwidth. It requires more than 384kbps, and cannot use the existing non-broadband Internet, and the operating cost is high; the software product can flexibly adjust the bandwidth, use the existing Internet or the customer's off-the-shelf network, and even reach the single Internet connection with the ordinary 56K modem dial-up Road remote video 4 frames / second.
Processing speed The video used in hardware video conferencing adopts the H.26x series and the G.7xx series used for audio through hardware encoding and decoding. Due to the large amount of video and audio data, in order to spread multimedia audio and video data in real time, it needs Hardware codec processing speed, these special hardware with special audio and video codec can well meet the requirements in this regard.
The software products mainly process audio and video data through software, which completely depends on the CPU of the host computer. When the computing power of the host computer is insufficient, it may cause a certain delay, but now the processor can already meet the requirements in this regard, and complete hardware The gap in product processing speed is getting smaller.
Transmission delay The transmission delay of the hardware video conference system is relatively small, which mainly comes from the unique functions of the private network. Networks such as ATM, Frame Relay, DDN, etc., provide a good guarantee for the transmission delay mechanism; and the video conference system based on IP network mainly runs on the X.25 backbone network, and the data processing is relative to the above The latency of the proposed network is greater.
The provided functions are hardware-based video conferencing systems, which generally only support a few simple functions such as electronic whiteboards and split-screen displays; while software-based conference systems can provide more functions according to customer requirements, such as simultaneous browsing of any format Files, data sharing, text exchange, meeting voting, convenient meeting recording and playback, intelligent meeting reminders, multiple meeting modes, setting someone as a speaker and driving someone out of the meeting room, etc.
Easy-to-operate hardware video conference system with simple functions and strong operability. The software video conference system is powerful and has a good humanized interface design. Just click the button according to the prompt to complete the desired operation.
Stability The hardware-based video conference system itself is based on the H.323 standard and has strong stability; the software-based video conference system may cause some stability problems due to the impact of encoding and operating platform and server load, but Can be gradually improved through comprehensive debugging.
The H.323 framework on which the security hardware is based is relatively mature and has a good security mechanism guaranteed by H.235. The products developed with independent property rights need to be designed by themselves in terms of safety.
The advantages of self-designed software for scalability are obvious. The self-developed video conference system is generally completely implemented in software, so it can be easily made into components or middleware products for secondary development and transplantation. For example, changing the four-channel video into two-channel video can be easily embedded into a web page and transformed into a video phone and online consultation system and other video applications. Once the hardware product is invested, the expandable range is much smaller, and there is no advantage in this respect.
The price of hardware video conferencing system is to buy special terminals and MCU and other equipment, but also a special network operating environment, the price is expensive. Many small and medium-sized enterprises and individuals are discouraged, which is also an important factor that the video conference system is not widely popularized; and the video conference system implemented by software only needs to use the existing PC or mobile PC to install ordinary audio and video recording equipment You can communicate, the price is cheap, suitable for small and medium-sized enterprises and individuals.
From the above analysis, it can be seen that in order to pursue the perfect video conference effect, large enterprise companies and government departments can choose a video conference system based on hardware and access a dedicated network. The software-implemented video conferencing system also has its great advantages. For small and medium-sized enterprises and individuals, you may wish to focus on the software video conferencing system and the network you can access to build your own video conferencing system.
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