Today, 28.8Kbps modems are the basic rate for Internet connections. Cable modems, ADSL, DSS, ISDN, etc. are developing rapidly. Content providers have to either restrict the quality of published media or limit the number of connected people. According to the statistics of the RealNetwork site, for the 28.8Kbps modem, the actual traffic is 10bps to 26Kbps, which has a bell-shaped distribution, with a peak at 20Kbps. This means that if the content provider chooses a fixed rate of 20Kbps, a large number of users will not get a good quality signal, and may stop the media stream and cause the client to buffer again until it receives enough data.
One solution is that the server reduces the data sent to the client to prevent rebuffering. In RealSystem 5.0, this method is called "video stream thinning". The limitation of this method is that the RealVideo file is designed for a data rate, and the result can be expanded to a lower rate by extracting internal frames, resulting in lower quality. The further away from the original data rate, the worse the quality. Another solution is to create multiple files according to different connection rates, and the server sends the corresponding file according to the user connection. This method brings difficulties in production and management. Moreover, the user connection is dynamic and the server cannot coordinate in real time. . Intelligent streaming technology overcomes bandwidth coordination and stream thinning in two ways. First, establish a coding framework that allows multiple streams of different rates to be encoded at the same time and merge into the same file; second, use a complex client / server mechanism to detect bandwidth changes.
In response to differences in software, device, and data transmission speeds, users browse audio and video content with different bandwidths. In order to meet customer requirements, Progressive Networks encodes and records media data at different rates and saves them in a single file. This file is called an intelligent streaming file, that is, an extensible streaming file is created. When the client sends a request, it transmits its bandwidth capacity to the server, and the media server transmits the corresponding part of the smart stream file to the user according to the client's bandwidth. In this way, users can see the most likely high-quality transmission, the production staff only needs to compress it once, the administrator only needs to maintain a single file, and the media server automatically switches according to the resulting bandwidth. Smart Streaming delivers high-quality media and guarantees reliability by describing the changing bandwidth characteristics of the Internet in the real world, and provides a solution to content authorization in a mixed connection environment. The streaming media is implemented as follows:
Create a file for all connection rate environments. Transfer media at different rates in a mixed environment. According to network changes, seamlessly switch to other rates. Key frame priority, audio is more important than some frame data. Backward compatibility with older versions of RealPlayer
Intelligent flow in RealSystem G2 is the realization of the so-called adaptive flow management (ASM) API. ASM describes the type of streaming data, assists intelligent decision-making, and determines which type of data packet is sent. The file format and broadcast plug-in define ASM rules. In the simplest form, assign predefined attributes and average bandwidth to packet groups. For the advanced form, the ASM rules allow the plug-in to change the packet transmission based on changes in network conditions. Each ASM rule can have a demonstration with defined conditions. For example, the demonstration defines that the customer bandwidth is 5,000 to 15,000 Kbps, and the packet loss is less than 2.5%. If this condition describes the customer's current network connection, the customer subscribes to this rule. The attributes defined in the rules help RealServer to effectively transmit data packets. If the network conditions change, customers subscribe to a different rule.
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