Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | Ogg Speex Audio Format |
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| Description | File format and bitstream encoding for for spoken content, targeted at a wide range of devices other than mobile phones. |
| Production phase | Generally used for final-state, end-user delivery. |
| Relationship to other formats | |
| Subtype of | Ogg, Ogg File Format |
| Contains | SPX_1_2, Speex Audio Codec, Version 1.2 |
| LC experience or existing holdings | The Library of Congress has a small amount of Ogg Speex Audio Format in its collections. |
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| LC preference | See the Library of Congress Recommended Formats Statement for format preferences for Audio Works. |
| Disclosure | Developed by xiph as an open source and patent-free project. |
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| Documentation | See Ogg and SPX_1_2. |
| Adoption | See Ogg. |
| Licensing and patents | See SPX_1_2. |
| Transparency | See SPX_1_2. |
| Self-documentation | See Ogg. |
| External dependencies | None. |
| Technical protection considerations | See Ogg. |
| Sound | |
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| Normal rendering | Good support. |
| Fidelity (high audio resolution) | See SPX_1_2. |
| Multiple channels | See SPX_1_2. |
| Support for user-defined sounds, samples, and patches | None. |
| Functionality beyond normal rendering | Not investigated at this time. |
| Tag | Value | Note |
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| Filename extension | spx |
The specification states that Speex tools (speexenc, speexdec) do not rely on the extension; any extension will work. |
| Internet Media Type | audio/x-speex |
For Speex-in-Ogg, from the main part of the specification. However, the recommended practice now seems to use the codecs parameter as described in RFC 5334. |
| Internet Media Type | audio/ogg; codecs=speex
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From RFC 5334. |
| Internet Media Type | audio/speex |
Proposed in various drafts of RTP Payload Format for the Speex Codec. e.g., http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-speex-05.txt (obsolete and hence not actively linked from this format description). |
| Magic numbers | Hex: 4F 67 67 53 00 02 00 00 00 00 00 00 00 00 ASCII: OggS |
See also Notes below. |
| Other | Speex |
Ogg Codec Identifier. An 8-character string, with 3 trailing spaces, used within Ogg container, at beginning of first header page to identify codec. See notes below and IETF RFC 5334 |
| Pronom PUID | fmt/948 |
See http://www.nationalarchives.gov.uk/PRONOM/fmt/948. |
| Wikidata Title ID | Q930667 |
See https://www.wikidata.org/wiki/Q930667. |
| General | Regarding file type signifiers, from the Speex specification: The first packet of the Ogg_SPX file contains the Speex header [presented in table 7.1 on page 25]. All integer fields in the headers are stored as little-endian. The speex_string field must contain the [Speex with 3 trailing spaces], which identifies the bit-stream. The next field, speex_version contains the version of Speex that encoded the file. For now, refer to speex_header.[ch] for more info. The beginning of stream (b_o_s) flag is set to 1 for the header. The header packet has packetno=0 and granulepos=0. The second packet contains the Speex comment header. The format used is the Vorbis comment format described here: https://xiph.org/vorbis/doc/v-comment.html. This packet has packetno=1 and granulepos=0. The third and subsequent packets each contain one or more (number found in header) Speex frames. These are identified with packetno starting from 2 and the granulepos is the number of the last sample encoded in that packet. The last of these packets has the end of stream (e_o_s) flag is set to 1. |
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| History |
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