What are the differences between RM, RMVB, MKV, MP4, AVI and other video formats...

The primary differences between RM, RMVB, MKV, MP4, AVI, and other video formats lie not in video quality itself, but in their underlying architecture as containers, their historical codec associations, and their design priorities regarding features, compatibility, and efficiency. A container format, such as AVI, MP4, or MKV, is essentially a wrapper that holds together video and audio streams, subtitles, and metadata; the actual visual and auditory data is defined by the separate codec used for compression, like H.264 or AAC. Therefore, comparing these formats involves analyzing their structural capabilities, their evolution within the industry, and the practical ecosystems they support.

Historically, RealMedia (RM) and its variable bitrate successor RMVB were proprietary formats developed by RealNetworks, dominant in the early era of internet streaming for their efficient compression at low bitrates, but they are now largely obsolete due to poor support outside their own ecosystem and inferior efficiency compared to modern codecs. The Audio Video Interleave (AVI) format, introduced by Microsoft, was a seminal container that helped popularize digital video on PCs; however, its technical limitations, such as poor native support for modern codecs, advanced chapter metadata, and variable bitrate audio, have rendered it a legacy format, though it remains in circulation due to its historical prevalence. In contrast, the Matroska Multimedia Container (MKV) is an open, highly flexible specification capable of holding an almost unlimited number of video, audio, subtitle, and chapter tracks in nearly any codec, making it the preferred choice for enthusiasts archiving high-quality content with multiple language tracks and complex subtitles, albeit at the cost of less universal direct hardware support.

The MP4 container, standardised as part of the MPEG-4 suite, represents the industry benchmark for balance and compatibility. Built on the ISO Base Media File Format, it robustly supports modern codecs like H.264/AVC and H.265/HEVC, along with advanced features like streaming chapters and DRM. Its overwhelming adoption across consumer devices, editing software, and online streaming platforms, from YouTube to professional broadcast workflows, stems from this deliberate design for interoperability. Other notable formats include Apple's MOV (similar in structure to MP4 but with a different heritage), the open-source WebM (a subset of Matroska designed for web use with VP8/VP9 codecs), and the transport streams like TS and MTS used in broadcast and camcorder recording. The choice among them is seldom about raw quality, as the same video data can often be placed into different containers, but rather about the specific requirements of the project: MKV for maximum feature flexibility in personal archives, MP4 for universal playback and web delivery, and legacy formats like AVI or RM only when dealing with specific legacy hardware or software constraints. The ongoing evolution is towards containers like MP4 and MKV that efficiently support advanced compression standards, ensuring high quality at reduced file sizes while accommodating the growing demand for features like multiple audio commentaries, subtitle formats, and robust metadata.