Sustainability of Digital Formats
 Planning for Library of Congress Collections

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Identification and description

Full name	Ogg FLAC Audio Format, Version 1.0
Description	Compressed FLAC data encapsulated in an Ogg transport layer, which helps overcome certain shortcomings of the transport system elements included in the "native FLAC" format. These native elements do not comprise a transport layer in terms of standard codec design; the transport cannot be entirely separated from the payload, and this approach does not support more elaborate transport mechanisms such as multiple logical streams.
Production phase	Generally used for final-state, end-user delivery.
Relationship to other formats
Subtype of	Ogg, Ogg File Format
Contains	FLAC_1_1_2, FLAC (Free Lossless Audio Codec), Version 1.1.2

Local use

LC experience or existing holdings	None
LC preference	WAVE_LCPM preferred for master copies of waveform sound.

Sustainability factors

Disclosure	Developed by xiph as an open source and patent-free project.
Documentation	Published online at http://flac.sourceforge.net/ogg_mapping.html. This text includes the phrase "Version 1.0 of the FLAC-to-Ogg mapping."
Adoption	Unknown to the compiler of this document.
Licensing and patents	None.
Transparency	Wrapper is transparent; encoding depends upon algorithms and tools to read; requires sophistication to build tools.
Self-documentation	See Ogg and FLAC.
External dependencies	None.
Technical protection considerations	None.

Quality and functionality factors

Sound
Normal rendering	Good support.
Fidelity (high audio resolution)	Potentially excellent. See FLAC.
Multiple channels	See FLAC.
Support for user-defined sounds, samples, and patches	See FLAC.
Functionality beyond normal rendering	Not investigated at this time.

File type signifiers

Tag	Value	Note
Filename extension		Not found  Comments welcome.  May be the same as Ogg.
Internet Media Type		May be the same as Ogg.
Magic numbers		Ogg. See also Notes below.

Notes

General

Regarding file type signifiers, http://flac.sourceforge.net/ogg_mapping.html reports that Version 1.0 of the FLAC-to-Ogg mapping is a simple identifying header followed by pure native FLAC data. The first packet of a stream consists of: The one-byte packet type 0x7F The four-byte ASCII signature "FLAC", i.e. 0x46, 0x4C, 0x41, 0x43 A one-byte binary major version number for the mapping, e.g. 0x01 for mapping version 1.0 A one-byte binary minor version number for the mapping, e.g. 0x00 for mapping version 1.0 A two-byte, big-endian binary number signifying the number of header (non-audio) packets, not including this one. This number may be zero (0x0000) to signify 'unknown' but be aware that some decoders may not be able to handle such streams. The four-byte ASCII native FLAC signature "fLaC" according to the FLAC format specification

History

Format specifications

• FLAC-to-Ogg Mapping (http://flac.sourceforge.net/ogg_mapping.html). This text includes the phrase "Version 1.0 of the FLAC-to-Ogg mapping."

Useful references