What do RM, WMA, AVI, RMVB and WMV mean in MP3 or video?

The audio and video compression standard developed by RealNetworks Company is called RealMedia. Users can use RealPlayer or RealOnePlayer to play network audio and video resources that meet the technical specifications of RealMedia. RealMedia can set different compression ratios according to different network transmission rates, so as to realize real-time transmission and playback of image data on low-rate networks. Another feature of this format is that users can use RealPlayer or RealOnePlayer to realize play online without downloading audio/video content. In addition, RM, as the mainstream network video format at present, can also convert videos in other formats into RM videos through its RealServer server, which is responsible for publishing and playing. RM and ASF formats can be said to have their own advantages. Generally, RM video is soft, while ASF video is relatively clear.

RM format has been positioned in the application of video streaming from the beginning, and it can also be said that it is the originator of video streaming technology. It can realize uninterrupted video playback under the condition of using 56K modem to dial up the Internet. Of course, its image quality has a certain gap compared with MPEG2-2 and DIVX. After all, it takes a lot of bandwidth to realize uninterrupted video transmission on the Internet.

RM format is a great contribution of Real Company to the multimedia world and also to the promotion of online movies. Its birth also makes streaming files known to more people. This kind of file can be played in real time, that is, some video files are downloaded from the server to form a video stream buffer and then played in real time, and at the same time, the download is continued to prepare for the next play. This way of "broadcasting while transmitting" avoids the disadvantage that users have to wait for the whole file to be downloaded from the Internet before they can watch it, so it is especially suitable for watching movies online. RM is mainly used for real-time transmission of compressed video on low-speed networks, and also has the characteristics of small size and clarity. The size of RM file depends entirely on the compression ratio chosen when making it, which is why sometimes we see that the image of 1 hour is only 200MB, while others are 500MB.

The full name of WMA is Windows Media Audio, which is a new audio format with the same name as the MP3 format introduced by Microsoft. WMA surpasses MP3 in compression ratio and sound quality, and is far superior to RA(Real Audio), so it can produce better sound quality even at a lower sampling frequency. Generally, WMA is used as the extension of files using Windows Media audio encoding format, and WMA is also used as the extension of some pure audio ASF files that use Windows Media audio encoding format to encode all their contents.

At the data rate of 64kbps, most information can be kept in the frequency band of 13000-20000Hz.

However, WMA's low frequency performance at 64kbps is somewhat disappointing. It sounds hard, just like adding wow effect, and it feels bad. Of course, it feels more concentrated than mp3 with the same bit. Auditively, the performance of 64WMA is basically close to the sound quality level of 128kbps mp3, but it does not reach it. Wma of 96K is slightly better than mp3 of 128K, and WMA is almost the same at various bit rates higher than 128, with rich high frequency and overtones. Most people can't hear the difference between sound quality and timbre above WMA 128Kbps. Generally speaking, WMA has a hard voice and is suitable for pop rock. If it is classical or pure vocal music, it feels a bit stiff, below. WMA above 128 will feel thinner than MP3.

WMA has completely surpassed MP3 format in the audition of code streams below 128kbps, and the king of low code streams is not in name only. However, when the code stream rose to 128kbp, the sound quality of WMA did not improve as much as that of MP3.

At present, all portable players support the most commonly used audio formats.

WMA (Wireless Messaging API) provides JAVA programs with the function of sending and receiving wireless information. WMA 1. 1 .

AVI is called audio-video interleaving in English, that is, audio-video interleaving format. This is a file format that combines voice and image synchronization. It uses lossy compression method for video files, but the compression rate is relatively high, so although the surface quality is not very good, it is still widely used. AVI supports 256 colors and RLE compression. AVI information is mainly used for multimedia CD-ROM, which is used to save various image information such as TV and movies.

It was introduced by Microsoft in 1992, and is known and familiar with people together with Windows3. 1. The so-called "audio and video interleaving" means that video and audio can be intertwined and played simultaneously. The advantage of this video format is that it has good picture quality and can be used across multiple platforms. Its disadvantage is that it is too big, and what is worse is that the compression standard is not uniform. The most common phenomenon is that the high version of Windows media player can't play the video in AVI format edited in the early stage, and the low version of Windows media player can't play the video in AVI format edited in the latest stage. Therefore, when we play some videos in AVI format, there are often some puzzling problems. For example, the video can't be played because of the video coding problem, or even if it can be played, there are some puzzling problems, such as the inability to adjust the playback progress, and only sound without images when playing. If users encounter these problems when playing video in AVI format, they can solve them by downloading the corresponding decoder. It is the mainstream of video files at present. Files in this format can be seen everywhere, such as the titles of some games and educational software, as well as multimedia CDs, which will have a lot of AVI.

Now, AVI can be played directly in WINDOWS 95 or 98, and there are several formats, the most common ones are Intel Indeo(R)Video R3.2, Microsoft video and so on.

Avi consists of three parts: file header, data block and index block.

The data block contains the actual data stream, that is, image and sound sequence data. This is the main body of the file and the main part that determines the file capacity. The size of a video file is equal to the data rate of the file multiplied by the length of playing the video, and the index block includes a list of data blocks and their positions in the file to provide random access to the data in the file. The file header includes general information of the file, data format definition, compression algorithm used and other parameters.

Navigation scheme

NAVI is the abbreviation of newAVI, which is a new video format developed by an underground organization called ShadowRealm (it has little to do with the AVI format mentioned above). It is modified from Microsoft ASF compression algorithm, but it is different from the ASF video format in the network video introduced below. It greatly improves the definition of ASF video files by increasing the frame rate at the expense of the video "streaming" characteristics of the original ASF video files.

DV-AVI format

The full English name of DV is Digital Video Format, which is a family digital video format jointly proposed by Sony, Panasonic, JVC and other manufacturers. At present, very popular digital cameras use this format to record video data. It can transmit video data to the computer through the IEEE 1394 port of the computer, and can also record the edited video data from the computer back to the digital camera. The file extension of this video format is usually. Avi, so it is also called DV-AVI format.

At present (June 5438+October 2007 10), the reason of AVI image inversion is probably the conflict between Storm Video and windows media player, which can be solved by downloading a complete DIVX decoder.

At the beginning of 1992, Microsoft introduced AVI technology and its application software VFW(Video for Windows). In AVI files, moving images and audio data are stored in a staggered way and are independent of hardware devices. This way of organizing audio and video data in an alternating way can obtain continuous information from storage media more effectively when reading video data streams. The main parameters of AVI file include video parameters, sound parameters and compression parameters.

AVI is not as complicated as MPEG, and it has existed since WIN3. 1. Its most direct advantages are good compatibility, convenient call and good picture quality, so it is often said to DVD. But its disadvantage is also obvious: large volume. It is precisely because of this that we have seen the birth of MPEG- 1 and MPEG-4. The AVI file size of a 2-hour image is almost the same as that of MPEG-2, but this is only for the standard resolution: the resolution of AVI can be adjusted at will according to different application requirements. The larger the window, the larger the data volume of the file. Reducing the resolution can greatly reduce its size, but the image quality is inevitably damaged. When the file size is similar to MPEG-2 format, the video quality of AVI format is relatively poor, but the requirements for computer configuration are not high. People usually record videos in AVI format first, and then convert them into other formats.

RmVB is a video file format. VB in RMVB refers to VBR (variable bit rate), which is much clearer than the previous generation RM format picture, because it reduces the bit rate under static picture and can be played by RealPlayer playback software.

The common rm format is real8.0 format, which adopts fixed rate coding. Many of them are Vcd-R M, which have been popular for a while. However, due to the congenital deficiency and lack of clarity of VCD film source, the rm pressed out will not be clear. Especially the standard online code rate of 225kbps, the definition is simply terrible.

RMVB has one more VB than RM, and VB means variable bit, that is, dynamic code rate! It is the new coding format 9.0 format of the real company. Rmvb(real9.0) and rm(real8.0) still use 8.0 format in audio coding. We use at least 32kbps sterero music when tabletting, usually 44K, and 96K for MTV. If it is higher, there is no need to compress it!

Now, for example:

If they are all 450K, the code rate is 450K for RM and 450 ~ 900 K for RMVB (double by default) according to the intensity of the picture. Finally, you will get an average code rate, such as 460.8K The following is a detailed explanation:

Because of the large amount of data and clear image quality, DVDRIP will get a clear effect when compressed into rmvb (of course, the code rate we use when compressing is also large). If you press rm format, that is, 8.0 format will be clearer, but not as good as rmvb. However, rm format has good compatibility and low requirements for cpu, so rmvb needs to be played on a high-profile machine to be smooth.

If the VCD is also in rmvb format, it is unnecessary, because rmvb does not mean that the file must be clear, but depends on the original movie file. If you want to get a clear rm/rmvb, you need high-definition original files, such as DVDRIP. The VCD format, that is, the bit rate of 1M, is almost the same as the original VCD at best.

This is the difference between the two. Here is just to remind everyone not to ignore rm because of rmvb. If VCD is pressed into real format, you should use real8.0 format, that is, rm, instead of rmvb of real9.0. For some DVDs such as life dramas and comics, you can use rm format of real8.0 instead of VBR encoding. This is a misunderstanding!

WMV is a streaming media format introduced by Microsoft, which is an upgrade and extension of ASF (Advanced Streaming Format) format. Under the same video quality, WMV format is very small, which is very suitable for playing and transmitting on the Internet. AVI file encapsulates video and audio in one file, and allows audio and video playback to be synchronized. Similar to DVD video format, AVI files support multiple video streams and audio streams.

WMV is not only developed based on Microsoft's own technology. Since the seventh edition (WMV 1), Microsoft has started to use its own non-standard MPEG-4 Part 2. However, since the ninth edition of WMV is an independent standard of SMPTE (42 1M, also called VC- 1), it is reasonable to believe that the development of WMV does not have its own proprietary encoding and decoding technology like MPEG-4. At present, there are 16 companies sharing the patent of VC- 1 (April 2006), and Microsoft is also one of the companies sharing the patent of MPEG-4 AVC/H.264.

Microsoft's WMV is still very influential. However, due to Microsoft's own limitations, its WMV application development is not smooth. First, WM9 is a product of Microsoft and must rely on Windows. Windows means that the decoding part should also have a PC, at least the motherboard of the PC. This greatly increases the cost of set-top boxes, thus affecting the popularity of video on demand. Secondly, the video transmission delay of WMV technology is very large, usually 10 second. Because of this restriction, WMV can only browse WM9 video files on the computer at present.

Wmv-HD is a video compression format created by Microsoft, a software giant, and is generally adopted. WMV as a file suffix. Its compression ratio is even higher than MPEG-2 standard, and it is also a 2-hour HDTV program. If MPEG-2 is used, it can only be compressed to 30GB at most, while if a high compression rate encoder such as WMV-HD is used, it can be compressed to less than 15GB, and the image quality is not degraded.

Based on WMV9 standard, WMV-HD is the latest version of video compression technology series developed by Microsoft. Although WMV-HD is a unique standard of Microsoft, it is rapidly popularized in desktop systems because it strongly supports WMV series versions in the operating system. In terms of performance, the data compression ratio of WMV-HD is the same as that of H.264, and its application fields are also very similar. Therefore, in the struggle for the dominance of the new generation of mainstream video coding standards, the two sides launched a tit-for-tat struggle, focusing on the next generation of optical disc specification "HD DVD" and digital microwave broadcasting and television.

Generally speaking, HDTV files use. The wmv suffix is compressed by WMV-HD.

At present, the DVD Forum has preliminarily approved Microsoft's MPEG-2, H.264 and WMA-HD as the mandatory standards of the next generation DVD, namely HD-DVD technology.

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