oggpage

Oggpage, or an Ogg page, is the fundamental data unit of the Ogg multimedia container format. It is used to multiplex multiple streams, such as audio and video, into a single file or stream while preserving synchronization and independent decoding.

An Ogg page consists of a header and a payload. The header begins with the capture pattern "OggS" and includes the version, a header type flag, the granule position, the bitstream serial number, the page sequence number, and a CRC. The header type flag can indicate the beginning of a stream (BOS) or the end of a stream (EOS). The granule position encodes, for many codecs, the total number of samples or the equivalent time reference up to the end of the page, enabling seeking. The serial number identifies the logical stream, while the page sequence number provides a monotonically increasing order for pages within that stream. The CRC protects the header and payload integrity.

Following the header is a segment table that specifies how the payload is divided into 0–255-byte segments. The sum of the segment sizes equals the length of the payload contained in the page. A single logical packet may span multiple pages, and a page may contain complete or partial packets.

In software, the ogg_page structure (often referred to as an ogg_page in code) represents this data unit. Libraries such as libogg provide APIs to read, write, and inspect pages, extract payloads, and navigate across pages and streams. The Ogg page design supports efficient streaming, random access within streams, and seamless multiplexing of multiple codecs within a single container. Common codecs used with Ogg include Vorbis, Theora, and Opus.