. RM is realvideo file, which is a new streaming video file format. It is included in realmedia, realvideo audio and video compression specification. RM is mainly used for real-time transmission of real-time video images on low-speed Wan, and different compression rates are used to realize real-time transmission and real-time playback of image data.
.RM 即 RealVideo 文件，是一种由百 RealNetworks 开发的新型流式视频文件格式，包含在 RealVideos 音频和视频压缩规范 RealMedia 中，主要用于在低速广域网上实时传输实时视频图像，使用不同的度问压缩率来实现图像数据的实时传输和实时回放。
. RM is realvideo file, which is a new streaming video file format developed by RealNetworks. It is included in realmedia, the realvideo audio and video compression specification. RM is mainly used for real-time transmission of real-time video images on low-speed Wan, using different compression rates to achieve real-time transmission and real-time playback of image data.
可以根据网络数据传输的不同速率制定不同的压缩比率，从而实现低速率的 Internet 上进行视频文件的实时传送和播放。它主要包含 RealAudio、RealVideo 和 RealFlash 三部分。
According to the different rate of network data transmission, different compression ratio can be set to realize the real-time transmission and playback of video files on the low rate Internet. It mainly includes RealAudio, realvideo and realflash.
rm 格式一开始就定位在视频流应用方面，也可以说是视频流技术的始创者。它可以在用 56K Modem 拨号上网的条件下实现不间断的视频播放，当然，其图像质量和 MPEG2，DIVX 等相比有一定差距，毕竟要实现在网上传输不间断的视频是需要很大带宽的。另外，rm 格式作为一种网络视频格式，它还可以通过其 RealServer 服务器将其它格式的视频转换成 rm 格式的视频并由 RealServer 服务器负责对外发布和播放。
RM format is located in the application of video streaming from the very beginning, which can also be said to be the originator of video streaming technology. It can play uninterrupted video on the condition of dial-up Internet with 56K modem. Of course, its image quality is different from MPEG2 and DivX. After all, it needs a lot of bandwidth to transmit uninterrupted video on the Internet. In addition, RM format as a network video format, it can also convert other formats of video into RM format video through its real server server, which is responsible for external publishing and playing.
rm 格式是 Real 公司对多媒体世界的一大贡献，也是对于在线影视推广的贡献。它的诞生，也使得流文件为更多人所知。这类文件可以实现即时播放，即先从服务器上下载一部分视频文件，形成视频流缓冲区后实时播放，同时继续下载，为接下来的播放做好准备。这种“边传边播”的方法避免了用户必须等待整个文件从 Internet 上全部下载完毕才能观看的缺点，因而特别适合在线观看影视。
RM format is a great contribution of real company to the multimedia world and also to the promotion of online film and television. Its birth also makes streaming files known to more people. This kind of files can realize real-time playback, that is, download some video files from the server first, form a video stream buffer, and then play them in real time, and continue to download at the same time, so as to prepare for the next playback. This method avoids the disadvantage that users have to wait for the entire file to be downloaded from the Internet to watch, so it is especially suitable for online viewing.
rm 格式主要用于在低速率的网上实时传输视频的压缩格式，它同样具有小体积而又比较清晰的特点。rm 格式的文件的大小完全取决于制作时选择的压缩率，这也是为什么有时我们会看到 1 小时的影像只有 200MB，而有的却有 500MB 之多。
RM format is mainly used for real-time transmission of video on low-speed network. It also has the characteristics of small size and clear. The size of RM file depends on the compression rate selected during production, which is why sometimes we can see that one hour’s image is only 200MB, while some are 500MB.