The MPEG Video Standards – from 1 to 21

If you're involved in digital media, there's no question you've encountered one of the MPEG standards for video. If you've ever listened to music on the Web you probably used a portion of the MPEG1 standard to do it (MP3). If you use an iPod, you're already knee-deep in MPEG4 (AAC audio). Ever watched a movie on DVD, or have DirecTV? You're already awash in MPEG2! But wait–there's more! The Moving Picture Experts Group - a working group of the ISO (International Organization for Standardization) - are busy folks, still working on ever more advanced standards for digital media.

The MPEG standards are all about interoperability. Generally, they are rules about how the systems and media files should interact with each other. Defining just the interfaces and behavior of the system leaves lots of room for innovation as to how things are implemented. For example, as MPEG1 technology has evolved over more than a decade, the encoders and decoders have improved – they're more efficient, have greater compression, faster performance, better-looking video, better-sounding audio. A high-end encoder will produce better-looking video than a low-end one, even though both are producing valid MPEG1 files at the same bitrate.

The Granddaddy of 'Em All - MPEG1
In development for years, MPEG1 became an official standard for encoding audio and video in 1992. The simplest of the MPEG standards, it describes a way to encode audio and video data streams, along with a way to decode them. MPEG1 may seem like an almost quaint spec in these days of super-codecs like WM9, RealVideo9, and MPEG4 -- but don't count it out. You can play it on just about any computer or operating system, and it doesn't take any special software or a lot of CPU horsepower to decode. And it's a sure bet that in ten years, you'll still be able to open and play those MPEG1 files in your archive.

The default size for an MPEG1 video is 352x240 at 30fps for NTSC (352x288 at 25fps for PAL sources). These were designed to give the correct 4:3 aspect ratio when displayed on the rectangular pixels of TV screens. For a computer-based viewing audience, 320x240 square pixels gives the same aspect ratio. Good up to about 1.5Mbps, MPEG1 delivers roughly VHS quality at 30 frames per second. You can scale up or down in size or bitrate, but from 1.2-1.5Mbps is the sweet spot where you'll get the most bang for your bitrate buck.