Lines Matching full:skeleton
6 <title>The Ogg Skeleton Metadata Bitstream</title>
73 <h1>The Ogg Skeleton Metadata Bitstream</h1>
77 <p><strong>Ogg Skeleton</strong> provides structuring information for multitrack <a href="//xiph.org/ogg">Ogg</a> files. It is compatible with Ogg <a rel="external" href="//theora.org">Theora</a> and provides extra clues for synchronization and content negotiation such as language selection.</p>
83 <p>Ogg Skeleton is being designed to overcome these problems. Ogg Skeleton is a logical bitstream within an Ogg stream that contains information about the other encapsulated logical bitstreams. For each logical bitstream it provides information such as its media type, and explains the way the granulepos field in Ogg pages is mapped to time.</p>
85 <p>Ogg Skeleton is also designed to allow the creation of substreams from Ogg physical bitstreams that retain the original timing information. For example, when cutting out the segment between the 7th and the 59th second of an Ogg file, it would be nice to continue to start this cut out file with a playback time of 7 seconds and not of 0. This is of particular interest if you're streaming this file from a Web server after a query for a temporal subpart such as in http://example.com/video.ogv?t=7-59</p>
91 <p>The following information about a logical bitstream is of interest to contain as meta information in the Skeleton:</p>
106 <p>When cutting out a subpart of an Ogg physical bitstream, the aim is to keep all the content pages intact (including the framing and granule positions) and just change some information in the Skeleton that allows reconstruction of the accurate time mapping. When remultiplexing such a bitstream, it is necessary to take into account all the different contained logical bitstreams. A given cut-in time maps to several different byte positions in the Ogg physical bitstream because each logical bitstream has its relevant information for that time at a different location. In addition, the resolution of each logical bitstream may not be high enough to accommodate for the given cut-in time and thus there may be some surplus information necessary to be remuxed into the new bitstream.</p>
108 <p>The following information is necessary to be added to the Skeleton to allow a correct presentation of a subpart of an Ogg bitstream:</p>
114 <h3>Ogg Skeleton version 3.0 Format Specification</h3>
116 <p>Adding the above information into an Ogg bitstream without breaking existing Ogg functionality and code requires the use of a logical bitstream for Ogg Skeleton. This logical bitstream may be ignored on decoding such that existing players can still continue to play back Ogg files that have a Skeleton bitstream. Skeleton enriches the Ogg bitstream to provide meta information about structure and content of the Ogg bitstream.</p>
118 <p>The Skeleton logical bitstream starts with an ident header that contains information about all of the logical bitstreams and is mapped into the Skeleton bos page. The first 8 bytes provide the magic identifier "fishead\0".
119 After the fishead follows a set of secondary header packets, each of which contains information about one logical bitstream. These secondary header packets are identified by an 8 byte code of "fisbone\0". The Skeleton logical bitstream has no actual content packets. Its eos page is included into the stream before any data pages of the other logical bitstreams appear and contains a packet of length 0.</p>
161 <p>The version fields provide version information for the Skeleton track, currently being 3.0 (the number having evolved within the Annodex project).</p>
205 <p>A further restriction on how to encapsulate Skeleton into Ogg is proposed to allow for easier parsing:</p>
207 <li>there can only be one Skeleton logical bitstream in a Ogg bitstream</li>
208 <li>the Skeleton bos page is the very first bos page in the Ogg stream such that it can be identified straight away and decoders don't get confused about it being e.g. Ogg Vorbis without this meta information</li>
210 <li>the secondary header pages of all logical bitstreams come next, including Skeleton's secondary header packets</li>
211 <li>the Skeleton eos page end the control section of the Ogg stream before any content pages of any of the other logical bitstreams appear</li>
