\section{Semantics of seeking in Ogg bitstreams}
\label{group__seek__semantics}\index{Semantics of seeking in Ogg bitstreams@{Semantics of seeking in Ogg bitstreams}}
\subsection{Introduction}\label{group__seek__semantics_seek_semantics_intro}
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The seeking semantics of the Ogg file format were outlined by Monty in {\tt a post to theora-\/dev} in September 2002. Quoting from that post, we have the following assumptions\+:


\begin{DoxyItemize}
\item Ogg is not a non-\/linear format. ... It is a media transport format designed to do nothing more than deliver content, in a stream, and have all the pieces arrive on time and in sync.
\item The Ogg layer does not know the specifics of the codec data it\textquotesingle{}s multiplexing into a stream. It knows nothing beyond \textquotesingle{}Oooo, packets!\textquotesingle{}, that the packets belong to different buckets, that the packets go in order, and that packets have position markers. Ogg does not even have a concept of \textquotesingle{}time\textquotesingle{}; it only knows about the sequentially increasing, unitless position markers. It is up to higher layers which have access to the codec A\+P\+Is to assign and convert units of framing or time.
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(For more details on the structure of Ogg streams, see the \doxyref{Ogg Basics }{p.}{group__basics} section).

For data such as media, for which it is possible to provide a mapping such as \textquotesingle{}time\textquotesingle{}, Oggz can efficiently navigate through an Ogg stream by use of an Oggz\+Metric callback, thus allowing automatic seeking to points in \textquotesingle{}time\textquotesingle{}.

For common codecs you can ask Oggz to set this for you automatically by instantiating the O\+G\+GZ handle with the O\+G\+G\+Z\+\_\+\+A\+U\+TO flag set. For others you can specify a multiplier with \doxyref{oggz\+\_\+set\+\_\+metric\+\_\+linear()}{p.}{oggz__deprecated_8h_a12f232bca448853e66a1226ddccff7e0}, or a generic non-\/linear metric with \doxyref{oggz\+\_\+set\+\_\+metric()}{p.}{group__metric_ga5a630e8dcd04e1dd6601d8f56f0af3f6}. 