View source for TransOggChangesFromOgg

TransOgg is intended to be the next major revision of the Ogg container.  The major changes over the original container are summarized below.

= Transport Changes =

== Full stream metadata on every packet ==

Most containers replicate some codec data into the container layer for ease of implementation, balancing overhead/complexity with convenience.  This pushes back (but does not eliminate) the need for a codec-specific 'stubs' or 'packetizers'.

The original Ogg design took a 'maximally minimalist' stance on stream
metadata, not replicating any data into the container layer that could
be provided by a codec stub.  This was not a popular design decision
to put it mildly, mainly because it pushed more of the implementation
work out of the container lib and onto external framework implementors.

For that reason, transOgg goes the opposite direction.  It stamps full
container metadata on every packet, pushing back the need for
packetizers even further, and hopefully saving more work.

== Generalized/formalized timing and interleave metadata ==

The timing, interleave, structure, and codec-specific fields must be
fully generalized, specified and declared by the container.

== New lacing scheme ==

Packet size encoding is tweaked to use a new extension pivot; rather
than extending the packet size encoding from an extension value of
255, the new pivot is 252.  This allows the length of any packet
segment in a page to be encoded in at most three bytes, preserves
small-packet encoding efficiency and also allows signalling for runs
of zero-packets in null-packet based VFR schemes.

= Metadata =

As in the original Ogg design, metadata is encapsulated within the
low-level transport as a stream.  Unlike the original Ogg, transOgg
metadata is mandatory and necessary for stream operation.  Metadata
uses stream ID 0 in all links.  All other stream IDs must be unique to
the complete stream.

== Structural metadata ==

This is the essential metadata required for operation of the
transOgg's mux layer.  As in the original Ogg, no metadata is required
to capture, parse and recover packets from the page stream, however
structural metadata is required to interpret many of the values
contained in the page.  This data exists in the form of a
header/footer pair and is mandatory.

* Per-stream metadata, such as timing, sync/order flags, codec flags, etc.
* Mandatory stream-global information (enumeration of codecs)
* Per-stream codec setup information (codec headers)
* seeking index (optional)
* Chaining linkage

== Semantic metadata ==

This is metadata used to properly present or semantically augment the
data of the stream itself.

* Stream relationships (primary/secondary angles, languages, overlays, etc)
* Non-linear features such as chapters
* Fixed (header/footer) and streamable semantic metadata
* Streamed (rolling) headers for in-band capture

= More Information =

* [[TransOgg]]: Toplevel transOgg page