With the development of modern network technology, the network as the fourth media begins to bring more form of information mode. From the Internet, the first picture appeared on the network, and now various forms of online video, three-dimensional animation, people's audio-visual sensation officials have been greatly satisfied on the network. At the same time, it is facing another inevitable embarrassment: It is because of the continuous improvement of people's needs, the increasing number of Internet users, plus the limitations of network hardware devices, making the size of the file become a non-negligible parameter of the network. On the one hand, people want to see vivid and clear media demonstrations on the Internet, and in the other hand, people have to face a lot of time required for file transmission under this slow network speed. In order to solve this contradiction, a new media technology came into being, this is "streaming media technology".
I don't know if you start to know such technologies. In my impression, Flash technology is the first to bring me the concept of "stream". Includes subsequent Shockwave for Authorware, Shockwave for Director, etc. The latest network 3D image standard, the same is the flow-type propagation technology, and examples are very hot recently, and the effect is really good for ViewPoiInt (Metastream) and Cult3D technology. Of course, I also use the concept of streaming in QTVR. We are not mentioned here.
The above may only be aligheated out, we mainly introduce the system of streaming media for network video transmission applications, mainly REAL SYSTEM and MedIA Service, of course there is QuickTime. As for a Cisco IP / TV, a class system, due to a small range of use, the time and occasion of the time and occasion, do not do detailed research.
No matter which system, their basic principles are the same: first, by using an efficient compression algorithm, the original massive multimedia data is suitable for streaming of streaming while reducing the loss of the file size while reducing the size of the file. Then, the MIME ID is then modified by the frame. Transport stream data through various real-time protocols.
Real-time flow transfer agreements include:
Real-time transport protocol RTP. RTP (Real-TimetransportProtocol)
Real-time transmission control protocol RTCP. RTCP (Real-TimetransportControlProtocol)
Real-time flow protocol RTSP. Real-time flow protocol RTSP (RealTimeStreamingProtocol)
RSVP protocol. RSVP (ResourceRereveProtocol)
MMS Agreement: Microsoft Media Server Protocol (MMS Protocol)
Below we use comparison methods to do some more detailed introductions for these systems:
1. Overview
Microsoft's core of Windowsmedia is ASF (AdvancedStreamFormat). ASF is a data format, audio, video, image, and control command script, etc., through this format, transmitted in the form of network packets, and implements streaming multimedia content.
RealNetworks's RealMedia includes three types of files in Reaudio, Realvideo and RealFlash. . RealNetworks has released Reaudio1.0 in 1995, ReaRaudio and Realvideo products have become the most popular solutions on the Internet.
Apple's QuickTime debut in 1991, is a multimedia technology platform developed by Apple, a multimedia technology platform developed by the Web website creation and CD-ROM content production. QuickTime supports almost all mainstream personal computing platforms, which is in the field of digital media. Industrial standards are important foundations for creating 3D animations, real-time effects, virtual reality, A / V and other digital streaming media. 2. Compression method
WM8: Of course, it is the latest version, using MPEG-4 compression encoding, we also see that his official version is much better than Beta version. Whether in the compression method of WMV or WMA, there is a big progress in the original V7. Supports TRUE-VBR (true dynamic variable rate encoding, which ensures quality of image during download) and TW-Pass encoding technology.
REAL: The REAL special algorithm is used, and the RA8 compression algorithm has recently increased. Through SVT (SCALABLEVIDETEHNOLOGY), the slower computer can not see all the original image data can also be smoothly viewed; two-way encoding (Two & # 0; Encoding) technology is similar to the VBR to select the limit selection to optimize the compression code rate. In order to better adapt to the online propagation, it can also select the REAL file of the best compression ratio according to the rate of MODEM, which is called SureStream technology. What we can't be denied is that in terms of network bandwidth, Real is much better than WM!
Qt: We can see that multiple encodings including H.263 can be selected when QT output files are available. However, it is mainly based on SorensonVideo, which is said to be MPEG-4 compression techniques from 5.0. QuickTime's voice CODEC is QUALCompurevolm, start supporting VBR from the QuickTime4.1 version. QuickTime's music CODEC is QDesiglmusic2.
3. Server and client
Windows Media
Server: The attached components of Windows Server, no number of client connections.
Client: Microsoft Free Player Windows Media Player, we can see its latest version 8 in the latest Windows XP.
REAL SYSTEM
Server: Real Server, free download, the latest distribution, such as Plus, Pro version, etc. Accessing the number of user connections is limited, through the license file, the file also has various functions management functions. The same server can achieve different functional permissions by pouring different LCENCE.
Client: Real Player Real Player, there are different versions, foundation Basic for free download, professional PLUS version needs to be paid. The PLUS version provides more image screen control, which is not available in Media Player. The latest version is: 6.0.9.584.
Quick Time
Server: Quick Time Street Server is a server under the Mac platform, a user connection restriction, a fixed number, a single Server allows a maximum connection of 4,000. There is Perl-based Darwin Streaming Server (PR3) under the PC platform. At the same time, REAL Server 8 also supports the MOV file in RTSP mode.
Client: Apple Player Quick Time. The same version is different, and the professional version requires paid acquisition, the professional version adds a simple editing of the MOV file. 4. Editing tools and expansion features
Windows Media
"Windows Media Encoder" Converts real-time and stored video and audio content as ASF streams, and then transmits in the network via the Windows Media server. The original version is integrated into a file called NetTools. Later versions have already been independent of it.
"Windows Media Author" is a tool developed by Microsoft and Digital Renaissance, Incorporated. This tool is used to assemble, synchronize and compressed videos and image files are single .asf files. The content created by Windows Media Author is called "Demo Audio" because it is similar to the slide demonstration of sound track. Windows Media Author also adds a scripted command and URL to .asf files.
"Windows Media Publish to Asf for Microsoft PowerPoint 97" is a tool that converts a narrate PowerPoint demo into a .asf file.
"Windows Media Plug-in for Adobe Premiere" can compress and convert video files as ASF files in Adobe Premiere. We can find it in the new version of Premiere6.
"VIDTOASF" and "WAVTOASF" are the conversion utility running from the server's command line. They are used to convert existing sounds and movie files for ASF format.
"Asfcheck" and "asfchop" are file utilities run from the server's command line. Asfcheck is used to verify .asf format, if possible, the file is also repaired. Asfchop is available to the .asf file new attribute, tag, index, and script command, and the time field that deletes .asf files.
In addition, after installing the SDK program related to Windows Media, we can find a file of NSScript.exe in the WMSSDK / Samples / Scrbld / Directory inside, using the NSScript.exe file to edit the ASF marker bit and Script jump, in WMSSDK / Samples / BATCH / Directory Locate a setup.exe for installing the Batch Encode Utility, which is a program for batch conversion.
ASX's file format reference details can be found in Microsoft Windows Media Player Control SDK in Windows Media SDK. This is a simpler programming language, but now there is no convenient graphical editing tool, or Gui. But I believe that MS will launch relevant auxiliary editing procedures soon. Because in this regard, Real has been walking in front of them.
With the ASX file, you can simply control play files. In ASX components, including flag components such as Title / Logo, the infrastructure such as entry, and the tag components such as STARTMARKER / Endmarker, and / EVENT interactive components Control elements such as REPEAT.
Here is an example of an ASX file:
<"ASX Version =" 3.0 "> Windows Media Technologies (C) 1999, Microsoft Corporation Windows Media Technologies (C) 1999, Microsoft Corporation Windows Media Technologies (C) 1999, Microsoft Corporation
Here is merely defined two standard video entries, as well as related author information.
It is impossible to use ASX's interaction, we can make up for this defect by writing a Java Scripts or other auxiliary language call by writing a web page by adding a Marker in ASF. It is also to say that Windows Media Rights Manager, this is a digital privilege authorization management software that is supported by the background database, which can be encrypted for each released ASF file and then manages the publishing file via a digital certificate. Unnecessary worry will be intercepted by the STREAMBOX software, because the user will perform a digital certificate confirmation, the user can copy the downloaded file, but another user is turned on when the file is opened There is no authentication certificate for the file on the user machine, and the system will reread the certificate. Digital certificates can be free or chargeable. This is largely inhibited the flood of piracy. Implement the copyright management of online media files. About Windows Media Rights Manager can be obtained in its help files and SDK files. We can also investigate the hobby distribution of online user groups through this software.
REAL
REAL Producer: The build tool for REAL file is now able to make a tool for a Real file except for it, and can also be output through the premiere plug in CleaNer 5. But the effects and detailed parameters settings are far without Real Producter. REAL Producer and Media Encoder are functional. All of them are the compression process before the multimedia video and audio is performed before the network transmission. Inevitable, there will be quality losses in this here. What compression is performed is that the user is defined according to the quality and type of the video source, and in the case where the network bandwidth is allowed, we use as high compression mode. At the same time, REAL also provides self-defined compression characteristics, including: Normal Motion Video / Smoothest Motion Video / Sharpest Motion Video / Three types, differences in the image of Sharpest Motion Video and Normal MotionVideo will be clearer, sharp, but at the same time Its action coherence will be lost, while the effect of Smoothest Motion Video is the opposite effect. At the same time, we can also see that "2-Pass Encoding" "Variable Bit Ency Encoding" is also mentioned earlier in the PRODUCER. We can also find a batch program similar to Windows Media: Rmbatch.exe, the difference is that the GUI is not available here, but it is necessary to enter the user's own way to enter.
Real slide show: This is a Software that is a slide, and "Windows Media Author" is similar to the role. It is some simple picture jump and transition effect, generating RP files (REAL PICTURE). In fact, in a simple SMI language, you can implement it, so I personally think that its feature is not substantially large.
Real Rrester: It is a tool similar to the "Windows Media Presener For Microsoft PowerPoint 97" function. Its essence is to save the PPT file in the form of recording and broadcasting in the same period. It is suitable for network teaching. Teachers can control the beginning of recording, then turn pages while lectures. Real will record the course content and the teacher's lecture sound in the form of SMI and division, and it is more worth mentioning that it can divide the entire recording process according to the frame structure built in the PPT. That is to say, according to the PPT built-in structure, divide a lesson into: First small section / paragraph / second, second section .... Dampoint is that the image quality is poor, but this is nothing " The conclusions resulting in the case of Windows Media Presener for Microsoft PowerPoint 97, which leads to this result is that their algorithm itself, because the effect of jitter is used to optimize graphics, but instead make it appear very clear font edge blurry. Such a product effect is not suitable for use in projection. Real Jukebox: A digital music software, but can be used in the conversion format, his conversion function of CD-RM is very strong, and the conversion function of CD-MP3 is also good. But when using it to play music, there are too many resources, not recommended.
Real extension features are powerful, highlighting in its support for SMIL language. SMIL is usually read as "smile", which is actually an open WWW Association (WORLDEWEBCONSORTIUM, W3C) proposal for streaming multimedia format design. Like HTML, SMIL also defines a mechanism identification language, and users can create multimedia presentations based on it. SMIL mechanism is similar to JavaScript and VBScript. The browser needs to understand how to handle the script, and thus can be adopted by a WWW Association standard that is integrated into the browser.
The main difference between SMIL and HTML is that HTML can only demonstrate hypertext data, and cannot be used for multimedia content. Using HTML, you can only provide multimedia by starting a secondary application or enables the player to provide multimedia at the same location on the page each time. SMIL is a mechanism that can be seen as a command file that controls the display of the audio, video and images to use the multimedia capabilities that have been provided on the workstation. SMIL gives the designer how to control more, when or where to play video and audio in the browser.
SMIL also provides more data types to handle multimedia. For example, REALNETWORKS's REALPIX and REALTEXT two technologies enable Site creators to control Reaudio, RealVideo, and RealFlash content.
REAL also provides marker markers within the file, the same, which is implanted by editing software, this editing software is the Real Editor built into the product. Control the attached action at the file playback by inserting Tag and Event, (equivalent to MARKER and Scripts in Windows Media). In fact, this feature is already very good in SMI synchronization, and it is not so important here.
Quick Time
Since QT is Apple's thing, more about it is completed on the Mac, which is convenient to QT editing on the PC, and we can use Premeire and QuickTmie Pro to make simple editing on MOV files. modify. But the effect is far from using professional software with professional software on the Mac.
The interactivity of the Qt file is the strongest, supporting multiple interactions. Also have files similar to Windows MEIDA and REAL, and jumps.
Qt also has good support for SMIL, or it should be in turn. So, the current web editor may start to change a concept, perhaps in the near future, the network's programming language will not be html but SMIL, do not say XML, at least in multimedia, SMIL has been made very well. 5. Latest development and prospects
Windows Media
The latest Windows Media Encode 8, not only has new breakthroughs, but also supports more different network data transmission rates and compression ratios: You can use 48kbps rates to play audio data streams close to CD sound quality, with 64kbps rate, play and CD Audio data stream equivalent to sound quality; the latest video coding significantly optimizes the processing of dynamic effects. Whether it is consistent with the officially known than WindowsMediaformat7, we can be sure that it does make people's expectation, WMV8 is still unique to provide TrueMotion-Picture-ReadyVideoCodec video format, with low gear The DSL / Cable connection rate (250 kbps) can achieve near VHS video quality (Near-VHSQuality, a resolution of 320 × 240, 24 frames per second).
With a DSL / Cable connection rate (500 kbps), the video quality of DVD (Near-Dvdquality, 640 × 480, 24 frames per second) is available.
REAL
Real Audio ENCODE 8 greatly increases REAL to the compression processing power of audio. By the way: Audio transmission under very low code flow, REAL is stronger than WM.
In Server: iPoint-PrincetonVideoImage provides RealSystem 8 Advertising Insert PVI technology that is suitable for broadcasters, iPoint can seamlessly insert a predetermined advertising program in RealSystem 8. (Streaming media is also an effective way. Study found that the streaming of the media is more than 5 times higher than the effect of the banner.)
Richfx-RealPlayer8 can display 3D effects in the original file 1/20 size. Richfx video technology can bring new business opportunities for narrowband e-commerce.
RealNetworks also launched RealSystemiq to establish a new generation of online broadcast nerve central systems.
RealNetworks, Inc. (NASDAQ: RNWK) Launches new technology RealSystemiq, which is the new foundation for the distribution of digital media. RealSystemiq In enhances the stability and reliability of online broadcasting, the broadcast information can spread to more viewers, but also bring better cost efficiency and elasticity for media dissemination.
In the past, the media's broadcasting was distributed to other streams through a central server, and then transmitted out users. The technology RealSystemiq is to reverse this one-way broadcast mode. RealSystemiq builds a honeycomb server group that allows each server to broadcast to the network, and receive content from other servers, and transmit digital media to users. NEURALALCAST technology establishes a differential basis that allows the digital media to transmit a number of servers by a server through a standard network protocol. In addition, RealSystemiq's architecture is allowed to be used to transmit a variety of formats. To achieve a more perfect transmission effect, RealSystemiq's area transfer function (TerrestrialMediAdelivery) adds more integrated support for satellite transfer technology.
Other manufacturers
RealNetworks gets support from NOKIA and other mobile phone manufacturers to develop its streaming sounds and images. We can see the latest NOKIA 9210 has supported Real.
US online era Warner, Bertelsmannag, EMI Group and RealNetworks announced an adventive cooperation program on Monday, that is, RealNetwork will launch online music service network - MusicNet, the above three US main music publishers are authorized to license their sons Company (Warner Music Group, BMG Entertainment, and EMI Records, which will give MusicNET "published music to MusicNET in non-selling methods. But we can see: In May 2000, Intel announced that the company will provide Internet service business for streaming media suppliers. It is designed to provide streaming media infrastructure for some companies, and also enable media and content providers such as concerts, movies, broadcasts, briefings to pass the Internet, with high quality flow content .........
In February 2001, Intel announced that it will gradually withdraw business. He emphasized that the company believes that the prospects of the online stream and video development are good, but it is not a timing.
No one wants to become the mainstream of this industry, because they see the broad prospect of the development of streaming media, and there is a media statistically reported that the leading advantages in home users have further increased, and the media said that the growth rate of WM is 4 times the growth of REAL. But in any case, we will try it, then pay. Bring the latest best technical solutions.
