MPEG1s

MPEG-1 refers to a family of standards developed by the Moving Picture Experts Group (MPEG) and published by ISO/IEC in 1993 as ISO/IEC 11172. It covers the encoding of both video and audio data at relatively low bitrates and includes three parts: Systems, Video (MPEG-1 Part 2), and Audio (MPEG-1 Part 3). A typical MPEG-1 stream multiplexes an elementary video stream with one or more audio streams into a Program Stream or similar packaging format, enabling playback on consumer devices.

MPEG-1 video uses a block-based transform with discrete cosine transform and motion-compensated inter-picture prediction. It supports I-frames, P-frames, and B-frames, and typically employs 4:2:0 chroma subsampling. Resolutions common to early MPEG-1 video include CIF-like sizes such as 352x240 (NTSC) or 352x288 (PAL), at frame rates around 25–30 fps. The standard targets low to moderate bitrates, with Video CD commonly encoded around 1.5 Mbit/s for video, plus audio.

MPEG-1 audio defines three layers of audio coding: Layer I, II, and III; MPEG-1 Audio Layer III (MP3) became the most widely adopted variant. Layer III provides higher coding efficiency and is the basis for many digital music formats.

MPEG-1's Systems layer defines how the video and audio streams are multiplexed into a Program Stream and, for storage or transport on media such as CDs or tapes. The standard has largely been superseded by MPEG-2 for digital broadcasting and DVDs, but MPEG-1 streams remain in use in legacy media such as Video CDs and early online video.