1*4d5d8b54SAndroid Build Coastguard Worker<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 2*4d5d8b54SAndroid Build Coastguard Worker<html> 3*4d5d8b54SAndroid Build Coastguard Worker<head> 4*4d5d8b54SAndroid Build Coastguard Worker 5*4d5d8b54SAndroid Build Coastguard Worker<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-15"/> 6*4d5d8b54SAndroid Build Coastguard Worker<title>Ogg Documentation</title> 7*4d5d8b54SAndroid Build Coastguard Worker 8*4d5d8b54SAndroid Build Coastguard Worker<style type="text/css"> 9*4d5d8b54SAndroid Build Coastguard Workerbody { 10*4d5d8b54SAndroid Build Coastguard Worker margin: 0 18px 0 18px; 11*4d5d8b54SAndroid Build Coastguard Worker padding-bottom: 30px; 12*4d5d8b54SAndroid Build Coastguard Worker font-family: Verdana, Arial, Helvetica, sans-serif; 13*4d5d8b54SAndroid Build Coastguard Worker color: #333333; 14*4d5d8b54SAndroid Build Coastguard Worker font-size: .8em; 15*4d5d8b54SAndroid Build Coastguard Worker} 16*4d5d8b54SAndroid Build Coastguard Worker 17*4d5d8b54SAndroid Build Coastguard Workera { 18*4d5d8b54SAndroid Build Coastguard Worker color: #3366cc; 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81*4d5d8b54SAndroid Build Coastguard Worker margin: 0px; 82*4d5d8b54SAndroid Build Coastguard Worker margin-left: auto; 83*4d5d8b54SAndroid Build Coastguard Worker margin-right: auto; 84*4d5d8b54SAndroid Build Coastguard Worker margin-bottom: 1.5em; 85*4d5d8b54SAndroid Build Coastguard Worker background-color: #ffffff; 86*4d5d8b54SAndroid Build Coastguard Worker padding: 10px; 87*4d5d8b54SAndroid Build Coastguard Worker} 88*4d5d8b54SAndroid Build Coastguard Worker 89*4d5d8b54SAndroid Build Coastguard Worker#thepage { 90*4d5d8b54SAndroid Build Coastguard Worker margin-left: auto; 91*4d5d8b54SAndroid Build Coastguard Worker margin-right: auto; 92*4d5d8b54SAndroid Build Coastguard Worker width: 840px; 93*4d5d8b54SAndroid Build Coastguard Worker} 94*4d5d8b54SAndroid Build Coastguard Worker 95*4d5d8b54SAndroid Build Coastguard Worker</style> 96*4d5d8b54SAndroid Build Coastguard Worker 97*4d5d8b54SAndroid Build Coastguard Worker</head> 98*4d5d8b54SAndroid Build Coastguard Worker 99*4d5d8b54SAndroid Build Coastguard Worker<body> 100*4d5d8b54SAndroid Build Coastguard Worker<div id="thepage"> 101*4d5d8b54SAndroid Build Coastguard Worker 102*4d5d8b54SAndroid Build Coastguard Worker<div id="xiphlogo"> 103*4d5d8b54SAndroid Build Coastguard Worker <a href="http://www.xiph.org/"><img src="fish_xiph_org.png" alt="Fish Logo and Xiph.org"/></a> 104*4d5d8b54SAndroid Build Coastguard Worker</div> 105*4d5d8b54SAndroid Build Coastguard Worker 106*4d5d8b54SAndroid Build Coastguard Worker<h1>Ogg bitstream overview</h1> 107*4d5d8b54SAndroid Build Coastguard Worker 108*4d5d8b54SAndroid Build Coastguard Worker<p>This document serves as starting point for understanding the design 109*4d5d8b54SAndroid Build Coastguard Workerand implementation of the Ogg container format. If you're new to Ogg 110*4d5d8b54SAndroid Build Coastguard Workeror merely want a high-level technical overview, start reading here. 111*4d5d8b54SAndroid Build Coastguard WorkerOther documents linked from the <a href="index.html">index page</a> 112*4d5d8b54SAndroid Build Coastguard Workergive distilled technical descriptions and references of the container 113*4d5d8b54SAndroid Build Coastguard Workermechanisms. This document is intended to aid understanding. 114*4d5d8b54SAndroid Build Coastguard Worker 115*4d5d8b54SAndroid Build Coastguard Worker<h2>Container format design points</h2> 116*4d5d8b54SAndroid Build Coastguard Worker 117*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg is intended to be a simplest-possible container, concerned only 118*4d5d8b54SAndroid Build Coastguard Workerwith framing, ordering, and interleave. It can be used as a stream delivery 119*4d5d8b54SAndroid Build Coastguard Workermechanism, for media file storage, or as a building block toward 120*4d5d8b54SAndroid Build Coastguard Workerimplementing a more complex, non-linear container (for example, see 121*4d5d8b54SAndroid Build Coastguard Workerthe <a href="skeleton.html">Skeleton</a> or <a 122*4d5d8b54SAndroid Build Coastguard Workerhref="http://en.wikipedia.org/wiki/Annodex">Annodex/CMML</a>). 123*4d5d8b54SAndroid Build Coastguard Worker 124*4d5d8b54SAndroid Build Coastguard Worker<p>The Ogg container is not intended to be a monolithic 125*4d5d8b54SAndroid Build Coastguard Worker'kitchen-sink'. It exists only to frame and deliver in-order stream 126*4d5d8b54SAndroid Build Coastguard Workerdata and as such is vastly simpler than most other containers. 127*4d5d8b54SAndroid Build Coastguard WorkerElementary and multiplexed streams are both constructed entirely from a 128*4d5d8b54SAndroid Build Coastguard Workersingle building block (an Ogg page) comprised of eight fields 129*4d5d8b54SAndroid Build Coastguard Workertotalling twenty-eight bytes (the page header) a list of packet lengths 130*4d5d8b54SAndroid Build Coastguard Worker(up to 255 bytes) and payload data (up to 65025 bytes). The structure 131*4d5d8b54SAndroid Build Coastguard Workerof every page is the same. There are no optional fields or alternate 132*4d5d8b54SAndroid Build Coastguard Workerencodings. 133*4d5d8b54SAndroid Build Coastguard Worker 134*4d5d8b54SAndroid Build Coastguard Worker<p>Stream and media metadata is contained in Ogg and not built into 135*4d5d8b54SAndroid Build Coastguard Workerthe Ogg container itself. Metadata is thus compartmentalized and 136*4d5d8b54SAndroid Build Coastguard Workerlayered rather than part of a monolithic design, an especially good 137*4d5d8b54SAndroid Build Coastguard Workeridea as no two groups seem able to agree on what a complete or 138*4d5d8b54SAndroid Build Coastguard Workercomplete-enough metadata set should be. In this way, the container and 139*4d5d8b54SAndroid Build Coastguard Workercontainer implementation are isolated from unnecessary metadata design 140*4d5d8b54SAndroid Build Coastguard Workerflux. 141*4d5d8b54SAndroid Build Coastguard Worker 142*4d5d8b54SAndroid Build Coastguard Worker<h3>Streaming</h3> 143*4d5d8b54SAndroid Build Coastguard Worker 144*4d5d8b54SAndroid Build Coastguard Worker<p>The Ogg container is primarily a streaming format, 145*4d5d8b54SAndroid Build Coastguard Workerencapsulating chronological, time-linear mixed media into a single 146*4d5d8b54SAndroid Build Coastguard Workerdelivery stream or file. The design is such that an application can 147*4d5d8b54SAndroid Build Coastguard Workeralways encode and/or decode all features of a bitstream in one pass 148*4d5d8b54SAndroid Build Coastguard Workerwith no seeking and minimal buffering. Seeking to provide optimized 149*4d5d8b54SAndroid Build Coastguard Workerencoding (such as two-pass encoding) or interactive decoding (such as 150*4d5d8b54SAndroid Build Coastguard Workerscrubbing or instant replay) is not disallowed or discouraged, however 151*4d5d8b54SAndroid Build Coastguard Workerno container feature requires nonlinear access of the bitstream. 152*4d5d8b54SAndroid Build Coastguard Worker 153*4d5d8b54SAndroid Build Coastguard Worker<h3>Variable Bit Rate, Variable Payload Size</h3> 154*4d5d8b54SAndroid Build Coastguard Worker 155*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg is designed to contain any size data payload with bounded, 156*4d5d8b54SAndroid Build Coastguard Workerpredictable efficiency. Ogg packets have no maximum size and a 157*4d5d8b54SAndroid Build Coastguard Workerzero-byte minimum size. There is no restriction on size changes from 158*4d5d8b54SAndroid Build Coastguard Workerpacket to packet. Variable size packets do not require the use of any 159*4d5d8b54SAndroid Build Coastguard Workeroptional or additional container features. There is no optimal 160*4d5d8b54SAndroid Build Coastguard Workersuggested packet size, though special consideration was paid to make 161*4d5d8b54SAndroid Build Coastguard Workersure 50-200 byte packets were no less efficient than larger packet 162*4d5d8b54SAndroid Build Coastguard Workersizes. The original design criteria was a 2% overhead at 50 byte 163*4d5d8b54SAndroid Build Coastguard Workerpackets, dropping to a maximum working overhead of 1% with larger 164*4d5d8b54SAndroid Build Coastguard Workerpackets, and a typical working overhead of .5-.7% for most practical 165*4d5d8b54SAndroid Build Coastguard Workeruses. 166*4d5d8b54SAndroid Build Coastguard Worker 167*4d5d8b54SAndroid Build Coastguard Worker<h3>Simple pagination</h3> 168*4d5d8b54SAndroid Build Coastguard Worker 169*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg is a byte-aligned container with no context-dependent, optional 170*4d5d8b54SAndroid Build Coastguard Workeror variable-length fields. Ogg requires no repacking of codec data. 171*4d5d8b54SAndroid Build Coastguard WorkerThe page structure is written out in-line as packet data is submitted 172*4d5d8b54SAndroid Build Coastguard Workerto the streaming abstraction. In addition, it is possible to 173*4d5d8b54SAndroid Build Coastguard Workerimplement both Ogg mux and demux as MT-hot zero-copy abstractions (as 174*4d5d8b54SAndroid Build Coastguard Workeris done in the Tremor sourcebase). 175*4d5d8b54SAndroid Build Coastguard Worker 176*4d5d8b54SAndroid Build Coastguard Worker<h3>Capture</h3> 177*4d5d8b54SAndroid Build Coastguard Worker 178*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg is designed for efficient and immediate stream capture with 179*4d5d8b54SAndroid Build Coastguard Workerhigh confidence. Although packets have no size limit in Ogg, pages 180*4d5d8b54SAndroid Build Coastguard Workerare a maximum of just under 64kB meaning that any Ogg stream can be 181*4d5d8b54SAndroid Build Coastguard Workercaptured with confidence after seeing 128kB of data or less [worst 182*4d5d8b54SAndroid Build Coastguard Workercase; typical figure is 6kB] from any random starting point in the 183*4d5d8b54SAndroid Build Coastguard Workerstream. 184*4d5d8b54SAndroid Build Coastguard Worker 185*4d5d8b54SAndroid Build Coastguard Worker<h3>Seeking</h3> 186*4d5d8b54SAndroid Build Coastguard Worker 187*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg implements simple coarse- and fine-grained seeking by design. 188*4d5d8b54SAndroid Build Coastguard Worker 189*4d5d8b54SAndroid Build Coastguard Worker<p>Coarse seeking may be performed by simply 'moving the tone arm' to a 190*4d5d8b54SAndroid Build Coastguard Workernew position and 'dropping the needle'. Rapid capture with 191*4d5d8b54SAndroid Build Coastguard Workeraccompanying timecode from any location in an Ogg file is guaranteed 192*4d5d8b54SAndroid Build Coastguard Workerby the stream design. From the acquisition of the first timecode, 193*4d5d8b54SAndroid Build Coastguard Workerall data needed to play back from that time code forward is ahead of 194*4d5d8b54SAndroid Build Coastguard Workerthe stream cursor. 195*4d5d8b54SAndroid Build Coastguard Worker 196*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg implements full sample-granularity seeking using an 197*4d5d8b54SAndroid Build Coastguard Workerinterpolated bisection search built on the capture and timecode 198*4d5d8b54SAndroid Build Coastguard Workermechanisms used by coarse seeking. As above, once a search finds 199*4d5d8b54SAndroid Build Coastguard Workerthe desired timecode, all data needed to play back from that time code 200*4d5d8b54SAndroid Build Coastguard Workerforward is ahead of the stream cursor. 201*4d5d8b54SAndroid Build Coastguard Worker 202*4d5d8b54SAndroid Build Coastguard Worker<p>Both coarse and fine seeking use the page structure and sequencing 203*4d5d8b54SAndroid Build Coastguard Workerinherent to the Ogg format. All Ogg streams are fully seekable from 204*4d5d8b54SAndroid Build Coastguard Workercreation; seekability is unaffected by truncation or missing data, and 205*4d5d8b54SAndroid Build Coastguard Workeris tolerant of gross corruption. Seek operations are neither 'fuzzy' nor 206*4d5d8b54SAndroid Build Coastguard Workerheuristic. 207*4d5d8b54SAndroid Build Coastguard Worker 208*4d5d8b54SAndroid Build Coastguard Worker<p>Seeking without use of an index is a major point of the Ogg 209*4d5d8b54SAndroid Build Coastguard Workerdesign. There two primary reasons why Ogg transport forgoes an index: 210*4d5d8b54SAndroid Build Coastguard Worker 211*4d5d8b54SAndroid Build Coastguard Worker<ol> 212*4d5d8b54SAndroid Build Coastguard Worker 213*4d5d8b54SAndroid Build Coastguard Worker<li>An index is only marginally useful in Ogg for the complexity 214*4d5d8b54SAndroid Build Coastguard Workeradded; it adds no new functionality and seldom improves performance 215*4d5d8b54SAndroid Build Coastguard Workernoticeably. Empirical testing shows that indexless interpolation 216*4d5d8b54SAndroid Build Coastguard Workersearch does not require many more seeks in practice than using an 217*4d5d8b54SAndroid Build Coastguard Workerindex would. 218*4d5d8b54SAndroid Build Coastguard Worker 219*4d5d8b54SAndroid Build Coastguard Worker<li>'Optional' indexes encourage lazy implementations that can seek 220*4d5d8b54SAndroid Build Coastguard Workeronly when indexes are present, or that implement indexless seeking 221*4d5d8b54SAndroid Build Coastguard Workeronly by building an internal index after reading the entire file 222*4d5d8b54SAndroid Build Coastguard Workerbeginning to end. This has been the fate of other containers that 223*4d5d8b54SAndroid Build Coastguard Workerspecify optional indexing. 224*4d5d8b54SAndroid Build Coastguard Worker 225*4d5d8b54SAndroid Build Coastguard Worker</ol> 226*4d5d8b54SAndroid Build Coastguard Worker 227*4d5d8b54SAndroid Build Coastguard Worker<p>In addition, it must be possible to create an Ogg stream in a 228*4d5d8b54SAndroid Build Coastguard Workersingle pass. Although an optional index can simply be tacked on the 229*4d5d8b54SAndroid Build Coastguard Workerend of the created stream, some software groups object to 230*4d5d8b54SAndroid Build Coastguard Workerend-positioned indexes and claim to be unwilling to support indexes 231*4d5d8b54SAndroid Build Coastguard Workernot located at the stream beginning. 232*4d5d8b54SAndroid Build Coastguard Worker 233*4d5d8b54SAndroid Build Coastguard Worker<p><i>All this said, it's become clear that an optional index is a 234*4d5d8b54SAndroid Build Coastguard Workerdemanded feature. For this reason, the <a 235*4d5d8b54SAndroid Build Coastguard Workerhref="http://wiki.xiph.org/Ogg_Index">OggSkeleton now defines a 236*4d5d8b54SAndroid Build Coastguard Workerproposed index.</a></i> 237*4d5d8b54SAndroid Build Coastguard Worker 238*4d5d8b54SAndroid Build Coastguard Worker<h3>Simple multiplexing</h3> 239*4d5d8b54SAndroid Build Coastguard Worker 240*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg multiplexes streams by interleaving pages from multiple elementary streams into a 241*4d5d8b54SAndroid Build Coastguard Workermultiplexed stream in time order. The multiplexed pages are not 242*4d5d8b54SAndroid Build Coastguard Workeraltered. Muxing an Ogg AV stream out of separate audio, 243*4d5d8b54SAndroid Build Coastguard Workervideo and data streams is akin to shuffling several decks of cards 244*4d5d8b54SAndroid Build Coastguard Workertogether into a single deck; the cards themselves remain unchanged. 245*4d5d8b54SAndroid Build Coastguard WorkerDemultiplexing is similarly simple (as the cards are marked). 246*4d5d8b54SAndroid Build Coastguard Worker 247*4d5d8b54SAndroid Build Coastguard Worker<p>The goal of this design is to make the mux/demux operation as 248*4d5d8b54SAndroid Build Coastguard Workertrivial as possible to allow live streaming systems to build and 249*4d5d8b54SAndroid Build Coastguard Workerrebuild streams on the fly with minimal CPU usage and no additional 250*4d5d8b54SAndroid Build Coastguard Workerstorage or latency requirements. 251*4d5d8b54SAndroid Build Coastguard Worker 252*4d5d8b54SAndroid Build Coastguard Worker<h3>Continuous and Discontinuous Media</h3> 253*4d5d8b54SAndroid Build Coastguard Worker 254*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg streams belong to one of two categories, "Continuous" streams and 255*4d5d8b54SAndroid Build Coastguard Worker"Discontinuous" streams. 256*4d5d8b54SAndroid Build Coastguard Worker 257*4d5d8b54SAndroid Build Coastguard Worker<p>A stream that provides a gapless, time-continuous media type with a 258*4d5d8b54SAndroid Build Coastguard Workerfine-grained timebase is considered to be 'Continuous'. A continuous 259*4d5d8b54SAndroid Build Coastguard Workerstream should never be starved of data. Examples of continuous data 260*4d5d8b54SAndroid Build Coastguard Workertypes include broadcast audio and video. 261*4d5d8b54SAndroid Build Coastguard Worker 262*4d5d8b54SAndroid Build Coastguard Worker<p>A stream that delivers data in a potentially irregular pattern or 263*4d5d8b54SAndroid Build Coastguard Workerwith widely spaced timing gaps is considered to be 'Discontinuous'. A 264*4d5d8b54SAndroid Build Coastguard Workerdiscontinuous stream may be best thought of as data representing 265*4d5d8b54SAndroid Build Coastguard Workerscattered events; although they happen in order, they are typically 266*4d5d8b54SAndroid Build Coastguard Workerunconnected data often located far apart. One example of a 267*4d5d8b54SAndroid Build Coastguard Workerdiscontinuous stream types would be captioning such as <a 268*4d5d8b54SAndroid Build Coastguard Workerhref="http://wiki.xiph.org/OggKate">Ogg Kate</a>. Although it's 269*4d5d8b54SAndroid Build Coastguard Workerpossible to design captions as a continuous stream type, it's most 270*4d5d8b54SAndroid Build Coastguard Workernatural to think of captions as widely spaced pieces of text with 271*4d5d8b54SAndroid Build Coastguard Workerlittle happening between. 272*4d5d8b54SAndroid Build Coastguard Worker 273*4d5d8b54SAndroid Build Coastguard Worker<p>The fundamental reason for distinction between continuous and 274*4d5d8b54SAndroid Build Coastguard Workerdiscontinuous streams concerns buffering. 275*4d5d8b54SAndroid Build Coastguard Worker 276*4d5d8b54SAndroid Build Coastguard Worker<h3>Buffering</h3> 277*4d5d8b54SAndroid Build Coastguard Worker 278*4d5d8b54SAndroid Build Coastguard Worker<p>A continuous stream is, by definition, gapless. Ogg buffering is based 279*4d5d8b54SAndroid Build Coastguard Workeron the simple premise of never allowing an active continuous stream 280*4d5d8b54SAndroid Build Coastguard Workerto starve for data during decode; buffering works ahead until all 281*4d5d8b54SAndroid Build Coastguard Workercontinuous streams in a physical stream have data ready and no further. 282*4d5d8b54SAndroid Build Coastguard Worker 283*4d5d8b54SAndroid Build Coastguard Worker<p>Discontinuous stream data is not assumed to be predictable. The 284*4d5d8b54SAndroid Build Coastguard Workerbuffering design takes discontinuous data 'as it comes' rather than 285*4d5d8b54SAndroid Build Coastguard Workerworking ahead to look for future discontinuous data for a potentially 286*4d5d8b54SAndroid Build Coastguard Workerunbounded period. Thus, the buffering process makes no attempt to fill 287*4d5d8b54SAndroid Build Coastguard Workerdiscontinuous stream buffers; their pages simply 'fall out' of the 288*4d5d8b54SAndroid Build Coastguard Workerstream when continuous streams are handled properly. 289*4d5d8b54SAndroid Build Coastguard Worker 290*4d5d8b54SAndroid Build Coastguard Worker<p>Buffering requirements in this design need not be explicitly 291*4d5d8b54SAndroid Build Coastguard Workerdeclared or managed in the encoded stream. The decoder simply reads as 292*4d5d8b54SAndroid Build Coastguard Workermuch data as is necessary to keep all continuous stream types gapless 293*4d5d8b54SAndroid Build Coastguard Workerand no more, with discontinuous data processed as it arrives in the 294*4d5d8b54SAndroid Build Coastguard Workercontinuous data. Buffering is implicitly optimal for the given 295*4d5d8b54SAndroid Build Coastguard Workerstream. Because all pages of all data types are stamped with absolute 296*4d5d8b54SAndroid Build Coastguard Workertiming information within the stream, inter-stream synchronization 297*4d5d8b54SAndroid Build Coastguard Workertiming is always maintained without the need for explicitly declared 298*4d5d8b54SAndroid Build Coastguard Workerbuffer-ahead hinting. 299*4d5d8b54SAndroid Build Coastguard Worker 300*4d5d8b54SAndroid Build Coastguard Worker<h3>Codec metadata</h3> 301*4d5d8b54SAndroid Build Coastguard Worker 302*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg does not replicate codec-specific metadata into the mux layer 303*4d5d8b54SAndroid Build Coastguard Workerin an attempt to make the mux and codec layer implementations 'fully 304*4d5d8b54SAndroid Build Coastguard Workerseparable'. Things like specific timebase, keyframing strategy, frame 305*4d5d8b54SAndroid Build Coastguard Workerduration, etc, do not appear in the Ogg container. The mux layer is, 306*4d5d8b54SAndroid Build Coastguard Workerinstead, expected to query a codec through a centralized interface, 307*4d5d8b54SAndroid Build Coastguard Workerleft to the implementation, for this data when it is needed. 308*4d5d8b54SAndroid Build Coastguard Worker 309*4d5d8b54SAndroid Build Coastguard Worker<p>Though modern design wisdom usually prefers to predict all possible 310*4d5d8b54SAndroid Build Coastguard Workerneeds of current and future codecs then embed these dependencies and 311*4d5d8b54SAndroid Build Coastguard Workerthe required metadata into the container itself, this strategy 312*4d5d8b54SAndroid Build Coastguard Workerincreases container specification complexity, fragility, and rigidity. 313*4d5d8b54SAndroid Build Coastguard WorkerThe mux and codec code becomes more independent, but the 314*4d5d8b54SAndroid Build Coastguard Workerspecifications become logically less independent. A codec can't do 315*4d5d8b54SAndroid Build Coastguard Workerwhat a container hasn't already provided for. Novel codecs are harder 316*4d5d8b54SAndroid Build Coastguard Workerto support, and you can do fewer useful things with the ones you've 317*4d5d8b54SAndroid Build Coastguard Workeralready got (eg, try to make a good splitter without using any codecs. 318*4d5d8b54SAndroid Build Coastguard WorkerSuch a splitter is limited to splitting at keyframes only, or building 319*4d5d8b54SAndroid Build Coastguard Workeryet another new mechanism into the container layer to mark what frames 320*4d5d8b54SAndroid Build Coastguard Workerto skip displaying). 321*4d5d8b54SAndroid Build Coastguard Worker 322*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg's design goes the opposite direction, where the specification 323*4d5d8b54SAndroid Build Coastguard Workeris to be as simple, easy to understand, and 'proofed' against novel 324*4d5d8b54SAndroid Build Coastguard Workercodecs as possible. When an Ogg mux layer requires codec-specific 325*4d5d8b54SAndroid Build Coastguard Workerinformation, it queries the codec (or a codec stub). This trades a 326*4d5d8b54SAndroid Build Coastguard Workermore complex implementation for a simpler, more flexible 327*4d5d8b54SAndroid Build Coastguard Workerspecification. 328*4d5d8b54SAndroid Build Coastguard Worker 329*4d5d8b54SAndroid Build Coastguard Worker<h3>Stream structure metadata</h3> 330*4d5d8b54SAndroid Build Coastguard Worker 331*4d5d8b54SAndroid Build Coastguard Worker<p>The Ogg container itself does not define a metadata system for 332*4d5d8b54SAndroid Build Coastguard Workerdeclaring the structure and interrelations between multiple media 333*4d5d8b54SAndroid Build Coastguard Workertypes in a muxed stream. That is, the Ogg container itself does not 334*4d5d8b54SAndroid Build Coastguard Workerspecify data like 'which steam is the subtitle stream?' or 'which 335*4d5d8b54SAndroid Build Coastguard Workervideo stream is the primary angle?'. This metadata still exists, but 336*4d5d8b54SAndroid Build Coastguard Workeris stored by the Ogg container rather than being built into the Ogg 337*4d5d8b54SAndroid Build Coastguard Workercontainer itself. Xiph specifies the 'Skeleton' metadata format for Ogg 338*4d5d8b54SAndroid Build Coastguard Workerstreams, but this decoupling of container and stream structure 339*4d5d8b54SAndroid Build Coastguard Workermetadata means it is possible to use Ogg with any metadata 340*4d5d8b54SAndroid Build Coastguard Workerspecification without altering the container itself, or without stream 341*4d5d8b54SAndroid Build Coastguard Workerstructure metadata at all. 342*4d5d8b54SAndroid Build Coastguard Worker 343*4d5d8b54SAndroid Build Coastguard Worker<h3>Frame accurate absolute position</h3> 344*4d5d8b54SAndroid Build Coastguard Worker 345*4d5d8b54SAndroid Build Coastguard Worker<p>Every Ogg page is stamped with a 64 bit 'granule position' that 346*4d5d8b54SAndroid Build Coastguard Workerserves as an absolute timestamp for mux and seeking. A few nifty 347*4d5d8b54SAndroid Build Coastguard Workerlittle tricks are usually also embedded in the granpos state, but 348*4d5d8b54SAndroid Build Coastguard Workerwe'll leave those aside for the moment (strictly speaking, they're 349*4d5d8b54SAndroid Build Coastguard Workerpart of each codec's mapping, not Ogg). 350*4d5d8b54SAndroid Build Coastguard Worker 351*4d5d8b54SAndroid Build Coastguard Worker<p>As previously mentioned above, granule positions are mapped into 352*4d5d8b54SAndroid Build Coastguard Workerabsolute timestamps by the codec, rather than being a hard timestamp. 353*4d5d8b54SAndroid Build Coastguard WorkerThis allows maximally efficient use of the available 64 bits to 354*4d5d8b54SAndroid Build Coastguard Workeraddress every sample/frame position without approximation while 355*4d5d8b54SAndroid Build Coastguard Workersupporting new and previously unknown timebase encodings without 356*4d5d8b54SAndroid Build Coastguard Workerneeding to extend or update the mux layer. When a codec needs a novel 357*4d5d8b54SAndroid Build Coastguard Workertimebase, it simply brings the code for that mapping along with it. 358*4d5d8b54SAndroid Build Coastguard WorkerThis is not a theoretical curiosity; new, wholly novel timebases were 359*4d5d8b54SAndroid Build Coastguard Workerdeployed with the adoption of both Theora and Dirac. "Rolling INTRA" 360*4d5d8b54SAndroid Build Coastguard Worker(keyframeless video) also benefits from novel use of the granule 361*4d5d8b54SAndroid Build Coastguard Workerposition. 362*4d5d8b54SAndroid Build Coastguard Worker 363*4d5d8b54SAndroid Build Coastguard Worker<h2>Ogg stream arrangement</h2> 364*4d5d8b54SAndroid Build Coastguard Worker 365*4d5d8b54SAndroid Build Coastguard Worker<h3>Packets, pages, and bitstreams</h3> 366*4d5d8b54SAndroid Build Coastguard Worker 367*4d5d8b54SAndroid Build Coastguard Worker<p>Ogg codecs place raw compressed data into <em>packets</em>. 368*4d5d8b54SAndroid Build Coastguard WorkerPackets are octet payloads containing the data needed for a single 369*4d5d8b54SAndroid Build Coastguard Workerdecompressed unit, eg, one video frame. Packets have no maximum size 370*4d5d8b54SAndroid Build Coastguard Workerand may be zero length. They do not generally have any framing 371*4d5d8b54SAndroid Build Coastguard Workerinformation; strung together, the unframed packets form a <em>logical 372*4d5d8b54SAndroid Build Coastguard Workerbitstream</em> of codec data with no internal landmarks. 373*4d5d8b54SAndroid Build Coastguard Worker 374*4d5d8b54SAndroid Build Coastguard Worker<div class="caption"> 375*4d5d8b54SAndroid Build Coastguard Worker <img src="packets.png"> 376*4d5d8b54SAndroid Build Coastguard Worker 377*4d5d8b54SAndroid Build Coastguard Worker <p> Packets of raw codec data are not typically internally framed. 378*4d5d8b54SAndroid Build Coastguard Worker When they are strung together into a stream without any container to 379*4d5d8b54SAndroid Build Coastguard Worker provide framing, they lose their individual boundaries. Seek and 380*4d5d8b54SAndroid Build Coastguard Worker capture are not possible within an unframed stream, and for many 381*4d5d8b54SAndroid Build Coastguard Worker codecs with variable length payloads and/or early-packet termination 382*4d5d8b54SAndroid Build Coastguard Worker (such as Vorbis), it may become impossible to recover the original 383*4d5d8b54SAndroid Build Coastguard Worker frame boundaries even if the stream is scanned linearly from 384*4d5d8b54SAndroid Build Coastguard Worker beginning to end. 385*4d5d8b54SAndroid Build Coastguard Worker 386*4d5d8b54SAndroid Build Coastguard Worker</div> 387*4d5d8b54SAndroid Build Coastguard Worker 388*4d5d8b54SAndroid Build Coastguard Worker<p>Logical bitstream packets are grouped and framed into Ogg pages 389*4d5d8b54SAndroid Build Coastguard Workeralong with a unique stream <em>serial number</em> to produce a 390*4d5d8b54SAndroid Build Coastguard Worker<em>physical bitstream</em>. An <em>elementary stream</em> is a 391*4d5d8b54SAndroid Build Coastguard Workerphysical bitstream containing only a single logical bitstream. Each 392*4d5d8b54SAndroid Build Coastguard Workerpage is a self contained entity, although a packet may be split and 393*4d5d8b54SAndroid Build Coastguard Workerencoded across one or more pages. The page decode mechanism is 394*4d5d8b54SAndroid Build Coastguard Workerdesigned to recognize, verify and handle single pages at a time from 395*4d5d8b54SAndroid Build Coastguard Workerthe overall bitstream. 396*4d5d8b54SAndroid Build Coastguard Worker 397*4d5d8b54SAndroid Build Coastguard Worker<div class="caption"> 398*4d5d8b54SAndroid Build Coastguard Worker <img src="pages.png"> 399*4d5d8b54SAndroid Build Coastguard Worker 400*4d5d8b54SAndroid Build Coastguard Worker <p> The primary purpose of a container is to provide framing for raw 401*4d5d8b54SAndroid Build Coastguard Worker packets, marking the packet boundaries so the exact packets can be 402*4d5d8b54SAndroid Build Coastguard Worker retrieved for decode later. The container also provides secondary 403*4d5d8b54SAndroid Build Coastguard Worker functions such as capture, timestamping, sequencing, stream 404*4d5d8b54SAndroid Build Coastguard Worker identification and so on. Not all of these functions are represented in the diagram. 405*4d5d8b54SAndroid Build Coastguard Worker 406*4d5d8b54SAndroid Build Coastguard Worker <p>In the Ogg container, pages do not necessarily contain 407*4d5d8b54SAndroid Build Coastguard Worker integer numbers of packets. Packets may span across page boundaries 408*4d5d8b54SAndroid Build Coastguard Worker or even multiple pages. This is necessary as pages have a maximum 409*4d5d8b54SAndroid Build Coastguard Worker possible size in order to provide capture guarantees, but packet 410*4d5d8b54SAndroid Build Coastguard Worker size is unbounded. 411*4d5d8b54SAndroid Build Coastguard Worker</div> 412*4d5d8b54SAndroid Build Coastguard Worker 413*4d5d8b54SAndroid Build Coastguard Worker 414*4d5d8b54SAndroid Build Coastguard Worker<p><a href="framing.html">Ogg Bitstream Framing</a> specifies 415*4d5d8b54SAndroid Build Coastguard Workerthe page format of an Ogg bitstream, the packet coding process 416*4d5d8b54SAndroid Build Coastguard Workerand elementary bitstreams in detail. 417*4d5d8b54SAndroid Build Coastguard Worker 418*4d5d8b54SAndroid Build Coastguard Worker<h3>Multiplexed bitstreams</h3> 419*4d5d8b54SAndroid Build Coastguard Worker 420*4d5d8b54SAndroid Build Coastguard Worker<p>Multiple logical/elementary bitstreams can be combined into a single 421*4d5d8b54SAndroid Build Coastguard Worker<em>multiplexed bitstream</em> by interleaving whole pages from each 422*4d5d8b54SAndroid Build Coastguard Workercontributing elementary stream in time order. The result is a single 423*4d5d8b54SAndroid Build Coastguard Workerphysical stream that multiplexes and frames multiple logical streams. 424*4d5d8b54SAndroid Build Coastguard WorkerEach logical stream is identified by the unique stream serial number 425*4d5d8b54SAndroid Build Coastguard Workerstamped in its pages. A physical stream may include a 'meta-header' 426*4d5d8b54SAndroid Build Coastguard Worker(such as the <a href="skeleton.html">Ogg Skeleton</a>) comprising its 427*4d5d8b54SAndroid Build Coastguard Workerown Ogg page at the beginning of the physical stream. A decoder 428*4d5d8b54SAndroid Build Coastguard Workerrecovers the original logical/elementary bitstreams out of the 429*4d5d8b54SAndroid Build Coastguard Workerphysical bitstream by taking the pages in order from the physical 430*4d5d8b54SAndroid Build Coastguard Workerbitstream and redirecting them into the appropriate logical decoding 431*4d5d8b54SAndroid Build Coastguard Workerentity. 432*4d5d8b54SAndroid Build Coastguard Worker 433*4d5d8b54SAndroid Build Coastguard Worker<div class="caption"> 434*4d5d8b54SAndroid Build Coastguard Worker <img src="multiplex1.png"> 435*4d5d8b54SAndroid Build Coastguard Worker 436*4d5d8b54SAndroid Build Coastguard Worker<p>Multiple media types are mutliplexed into a single Ogg stream by 437*4d5d8b54SAndroid Build Coastguard Workerinterleaving the pages from each elementary physical stream. 438*4d5d8b54SAndroid Build Coastguard Worker 439*4d5d8b54SAndroid Build Coastguard Worker</div> 440*4d5d8b54SAndroid Build Coastguard Worker 441*4d5d8b54SAndroid Build Coastguard Worker<p><a href="ogg-multiplex.html">Ogg Bitstream Multiplexing</a> specifies 442*4d5d8b54SAndroid Build Coastguard Workerproper multiplexing of an Ogg bitstream in detail. 443*4d5d8b54SAndroid Build Coastguard Worker 444*4d5d8b54SAndroid Build Coastguard Worker<h3>Chaining</h3> 445*4d5d8b54SAndroid Build Coastguard Worker 446*4d5d8b54SAndroid Build Coastguard Worker<p>Multiple Ogg physical bitstreams may be concatenated into a single new 447*4d5d8b54SAndroid Build Coastguard Workerstream; this is <em>chaining</em>. The bitstreams do not overlap; the 448*4d5d8b54SAndroid Build Coastguard Workerfinal page of a given logical bitstream is immediately followed by the 449*4d5d8b54SAndroid Build Coastguard Workerinitial page of the next.</p> 450*4d5d8b54SAndroid Build Coastguard Worker 451*4d5d8b54SAndroid Build Coastguard Worker<p>Each logical bitstream in a chain must have a unique serial number 452*4d5d8b54SAndroid Build Coastguard Workerwithin the scope of the full physical bitstream, not only within a 453*4d5d8b54SAndroid Build Coastguard Workerparticular <em>link</em> or <em>segment</em> of the chain.</p> 454*4d5d8b54SAndroid Build Coastguard Worker 455*4d5d8b54SAndroid Build Coastguard Worker<h3>Continuous and discontinuous streams</h3> 456*4d5d8b54SAndroid Build Coastguard Worker 457*4d5d8b54SAndroid Build Coastguard Worker<p>Within Ogg, each stream must be declared (by the codec) to be 458*4d5d8b54SAndroid Build Coastguard Workercontinuous- or discontinuous-time. Most codecs treat all streams they 459*4d5d8b54SAndroid Build Coastguard Workeruse as either inherently continuous- or discontinuous-time, although 460*4d5d8b54SAndroid Build Coastguard Workerthis is not a requirement. A codec may, as part of its mapping, choose 461*4d5d8b54SAndroid Build Coastguard Workeraccording to data in the initial header. 462*4d5d8b54SAndroid Build Coastguard Worker 463*4d5d8b54SAndroid Build Coastguard Worker<p>Continuous-time pages are stamped by end-time, discontinuous pages 464*4d5d8b54SAndroid Build Coastguard Workerare stamped by begin-time. Pages in a multiplexed stream are 465*4d5d8b54SAndroid Build Coastguard Workerinterleaved in order of the time stamp regardless of stream type. 466*4d5d8b54SAndroid Build Coastguard WorkerBoth continuous and discontinuous logical streams are used to seek 467*4d5d8b54SAndroid Build Coastguard Workerwithin a physical stream, however only continuous streams are used to 468*4d5d8b54SAndroid Build Coastguard Workerdetermine buffering depth; because discontinuous streams are stamped 469*4d5d8b54SAndroid Build Coastguard Workerby start time, they will always 'fall out' at the proper time when 470*4d5d8b54SAndroid Build Coastguard Workerbuffering the continuous streams. See 'Examples' for an illustration 471*4d5d8b54SAndroid Build Coastguard Workerof the buffering mechanism. 472*4d5d8b54SAndroid Build Coastguard Worker 473*4d5d8b54SAndroid Build Coastguard Worker<h2>Multiplexing Requirements</h2> 474*4d5d8b54SAndroid Build Coastguard Worker 475*4d5d8b54SAndroid Build Coastguard Worker<p>Multiplexing requirements within Ogg are straightforward. When 476*4d5d8b54SAndroid Build Coastguard Workerconstructing a single-link (unchained) physical bitstream consisting 477*4d5d8b54SAndroid Build Coastguard Workerof multiple elementary streams: 478*4d5d8b54SAndroid Build Coastguard Worker 479*4d5d8b54SAndroid Build Coastguard Worker<ol> 480*4d5d8b54SAndroid Build Coastguard Worker 481*4d5d8b54SAndroid Build Coastguard Worker<li><p> The initial header for each stream appears in sequence, each 482*4d5d8b54SAndroid Build Coastguard Workerheader on a single page. All initial headers must appear with no 483*4d5d8b54SAndroid Build Coastguard Workerintervening data (no auxiliary header pages or packets, no data pages 484*4d5d8b54SAndroid Build Coastguard Workeror packets). Order of the initial headers is unspecified. The 485*4d5d8b54SAndroid Build Coastguard Worker'beginning of stream' flag is set on each initial header. 486*4d5d8b54SAndroid Build Coastguard Worker 487*4d5d8b54SAndroid Build Coastguard Worker<li><p> All auxiliary headers for all streams must follow. Order 488*4d5d8b54SAndroid Build Coastguard Workeris unspecified. The final auxiliary header of each stream must flush 489*4d5d8b54SAndroid Build Coastguard Workerits page. 490*4d5d8b54SAndroid Build Coastguard Worker 491*4d5d8b54SAndroid Build Coastguard Worker<li><p>Data pages for each stream follow, interleaved in time order. 492*4d5d8b54SAndroid Build Coastguard Worker 493*4d5d8b54SAndroid Build Coastguard Worker<li><p>The final page of each stream sets the 'end of stream' flag. 494*4d5d8b54SAndroid Build Coastguard WorkerUnlike initial pages, terminal pages for the logical bitstreams need 495*4d5d8b54SAndroid Build Coastguard Workernot occur contiguously; indeed it may not be possible for them to do so. 496*4d5d8b54SAndroid Build Coastguard Worker</oL> 497*4d5d8b54SAndroid Build Coastguard Worker 498*4d5d8b54SAndroid Build Coastguard Worker<p><p>Each grouped bitstream must have a unique serial number within the 499*4d5d8b54SAndroid Build Coastguard Workerscope of the physical bitstream.</p> 500*4d5d8b54SAndroid Build Coastguard Worker 501*4d5d8b54SAndroid Build Coastguard Worker<h3>chaining and multiplexing</h3> 502*4d5d8b54SAndroid Build Coastguard Worker 503*4d5d8b54SAndroid Build Coastguard Worker<p>Multiplexed and/or unmultiplexed bitstreams may be chained 504*4d5d8b54SAndroid Build Coastguard Workerconsecutively. Such a physical bitstream obeys all the rules of both 505*4d5d8b54SAndroid Build Coastguard Workerchained and multiplexed streams. Each link, when unchained, must 506*4d5d8b54SAndroid Build Coastguard Workerstand on its own as a valid physical bitstream. Chained streams do 507*4d5d8b54SAndroid Build Coastguard Workernot mix or interleave; a new segment may not begin until all streams 508*4d5d8b54SAndroid Build Coastguard Workerin the preceding segment have terminated. </p> 509*4d5d8b54SAndroid Build Coastguard Worker 510*4d5d8b54SAndroid Build Coastguard Worker<h2>Codec Mapping Requirements</h2> 511*4d5d8b54SAndroid Build Coastguard Worker 512*4d5d8b54SAndroid Build Coastguard Worker<p>Each codec is allowed some freedom in deciding how its logical 513*4d5d8b54SAndroid Build Coastguard Workerbitstream is encapsulated into an Ogg bitstream (even if it is a 514*4d5d8b54SAndroid Build Coastguard Workertrivial mapping, eg, 'plop the packets in and go'). This is the 515*4d5d8b54SAndroid Build Coastguard Workercodec's <em>mapping</em>. Ogg imposes a few mapping requirements 516*4d5d8b54SAndroid Build Coastguard Workeron any codec. 517*4d5d8b54SAndroid Build Coastguard Worker 518*4d5d8b54SAndroid Build Coastguard Worker<ol> 519*4d5d8b54SAndroid Build Coastguard Worker 520*4d5d8b54SAndroid Build Coastguard Worker<li><p>The <a href="framing.html">framing specification</a> defines 521*4d5d8b54SAndroid Build Coastguard Worker'beginning of stream' and 'end of stream' page markers via a header 522*4d5d8b54SAndroid Build Coastguard Workerflag (it is possible for a stream to consist of a single page). A 523*4d5d8b54SAndroid Build Coastguard Workercorrect stream always consists of an integer number of pages, an easy 524*4d5d8b54SAndroid Build Coastguard Workerrequirement given the variable size nature of pages.</p> 525*4d5d8b54SAndroid Build Coastguard Worker 526*4d5d8b54SAndroid Build Coastguard Worker<li><p>The first page of an elementary Ogg bitstream consists of a single, 527*4d5d8b54SAndroid Build Coastguard Workersmall 'initial header' packet that must include sufficient information 528*4d5d8b54SAndroid Build Coastguard Workerto identify the exact CODEC type. From this initial header, the codec 529*4d5d8b54SAndroid Build Coastguard Workermust also be able to determine its timebase and whether or not it is a 530*4d5d8b54SAndroid Build Coastguard Workercontinuous- or discontinuous-time stream. The initial header must fit 531*4d5d8b54SAndroid Build Coastguard Workeron a single page. If a codec makes use of auxiliary headers (for 532*4d5d8b54SAndroid Build Coastguard Workerexample, Vorbis uses two auxiliary headers), these headers must follow 533*4d5d8b54SAndroid Build Coastguard Workerthe initial header immediately. The last header finishes its page; 534*4d5d8b54SAndroid Build Coastguard Workerdata begins on a fresh page. 535*4d5d8b54SAndroid Build Coastguard Worker 536*4d5d8b54SAndroid Build Coastguard Worker<p><p>As an example, Ogg Vorbis places the name and revision of the 537*4d5d8b54SAndroid Build Coastguard WorkerVorbis CODEC, the audio rate and the audio quality into this initial 538*4d5d8b54SAndroid Build Coastguard Workerheader. Vorbis comments and detailed codec setup appears in the larger 539*4d5d8b54SAndroid Build Coastguard Workerauxiliary headers.</p> 540*4d5d8b54SAndroid Build Coastguard Worker 541*4d5d8b54SAndroid Build Coastguard Worker<li><p>Granule positions must be translatable to an exact absolute 542*4d5d8b54SAndroid Build Coastguard Workertime value. As described above, the mux layer is permitted to query a 543*4d5d8b54SAndroid Build Coastguard Workercodec or codec stub plugin to perform this mapping. It is not 544*4d5d8b54SAndroid Build Coastguard Workernecessary for an absolute time to be mappable into a single unique 545*4d5d8b54SAndroid Build Coastguard Workergranule position value. 546*4d5d8b54SAndroid Build Coastguard Worker 547*4d5d8b54SAndroid Build Coastguard Worker<li><p>Codecs are not required to use a fixed duration-per-packet (for 548*4d5d8b54SAndroid Build Coastguard Workerexample, Vorbis does not). the mux layer is permitted to query a 549*4d5d8b54SAndroid Build Coastguard Workercodec or codec stub plugin for the time duration of a packet. 550*4d5d8b54SAndroid Build Coastguard Worker 551*4d5d8b54SAndroid Build Coastguard Worker<li><p>Although an absolute time need not be translatable to a unique 552*4d5d8b54SAndroid Build Coastguard Workergranule position, a codec must be able to determine the unique granule 553*4d5d8b54SAndroid Build Coastguard Workerposition of the current packet using the granule position of a 554*4d5d8b54SAndroid Build Coastguard Workerpreceding packet. 555*4d5d8b54SAndroid Build Coastguard Worker 556*4d5d8b54SAndroid Build Coastguard Worker<li><p>Packets and pages must be arranged in ascending 557*4d5d8b54SAndroid Build Coastguard Workergranule-position and time order. 558*4d5d8b54SAndroid Build Coastguard Worker 559*4d5d8b54SAndroid Build Coastguard Worker</ol> 560*4d5d8b54SAndroid Build Coastguard Worker 561*4d5d8b54SAndroid Build Coastguard Worker<h2>Examples</h2> 562*4d5d8b54SAndroid Build Coastguard Worker 563*4d5d8b54SAndroid Build Coastguard Worker<em>[More to come shortly; this section is currently being revised and expanded]</em> 564*4d5d8b54SAndroid Build Coastguard Worker 565*4d5d8b54SAndroid Build Coastguard Worker<p>Below, we present an example of a multiplexed and chained bitstream:</p> 566*4d5d8b54SAndroid Build Coastguard Worker 567*4d5d8b54SAndroid Build Coastguard Worker<p><img src="stream.png" alt="stream"/></p> 568*4d5d8b54SAndroid Build Coastguard Worker 569*4d5d8b54SAndroid Build Coastguard Worker<p>In this example, we see pages from five total logical bitstreams 570*4d5d8b54SAndroid Build Coastguard Workermultiplexed into a physical bitstream. Note the following 571*4d5d8b54SAndroid Build Coastguard Workercharacteristics:</p> 572*4d5d8b54SAndroid Build Coastguard Worker 573*4d5d8b54SAndroid Build Coastguard Worker<ol> 574*4d5d8b54SAndroid Build Coastguard Worker<li>Multiplexed bitstreams in a given link begin together; all of the 575*4d5d8b54SAndroid Build Coastguard Workerinitial pages must appear before any data pages. When concurrently 576*4d5d8b54SAndroid Build Coastguard Workermultiplexed groups are chained, the new group does not begin until all 577*4d5d8b54SAndroid Build Coastguard Workerthe bitstreams in the previous group have terminated.</li> 578*4d5d8b54SAndroid Build Coastguard Worker 579*4d5d8b54SAndroid Build Coastguard Worker<li>The ordering of pages of concurrently multiplexed bitstreams is 580*4d5d8b54SAndroid Build Coastguard Workergoverened by timestamp (not shown here); there is no regular 581*4d5d8b54SAndroid Build Coastguard Workerinterleaving order. Pages within a logical bitstream appear in 582*4d5d8b54SAndroid Build Coastguard Workersequence order.</li> 583*4d5d8b54SAndroid Build Coastguard Worker</ol> 584*4d5d8b54SAndroid Build Coastguard Worker 585*4d5d8b54SAndroid Build Coastguard Worker<div id="copyright"> 586*4d5d8b54SAndroid Build Coastguard Worker The Xiph Fish Logo is a 587*4d5d8b54SAndroid Build Coastguard Worker trademark (™) of Xiph.Org.<br/> 588*4d5d8b54SAndroid Build Coastguard Worker 589*4d5d8b54SAndroid Build Coastguard Worker These pages © 1994 - 2010 Xiph.Org. All rights reserved. 590*4d5d8b54SAndroid Build Coastguard Worker</div> 591*4d5d8b54SAndroid Build Coastguard Worker 592*4d5d8b54SAndroid Build Coastguard Worker</div> 593*4d5d8b54SAndroid Build Coastguard Worker</body> 594*4d5d8b54SAndroid Build Coastguard Worker</html> 595
