.spx File Extension

What kind of file is a .spx?

A .spx file most commonly contains speech compressed with the Speex codec inside an Ogg container. RFC 5334 registers .spx under audio/ogg specifically for an Ogg file containing only a Speex bitstream.¹ Speex was designed for voice rather than music and supports narrowband 8 kHz, wideband 16 kHz, and ultra-wideband 32 kHz audio.²

On macOS, the same suffix has a second important meaning: System Information saves hardware and software reports as .spx files. These are XML property lists that System Information can reopen.³ Check the contents before choosing an app:

• Speex audio starts as an Ogg stream with 4F 67 67 53 (OggS), and its first codec header contains Speex followed by three spaces.¹⁴
• A Mac system report normally begins with an XML declaration and an Apple property-list document type.

How do I open a .spx on my computer?

For Speex audio, use VLC on Windows, macOS, or Linux. VLC lists both Ogg and Speex support.⁵ FFmpeg can inspect and convert the stream, while Xiph.Org's speexdec decodes Speex files to PCM audio or plays them through an available sound device.⁶ Mobile and browser playback is less predictable because support for the Ogg container does not guarantee support for the Speex codec.

For a Mac system report, open System Information, then choose File > Open, or double-click the file when its association is intact. A text or property-list editor can inspect the XML, but System Information presents the report in its intended hierarchy. System reports can disclose installed software, hardware identifiers, network details, and other configuration data, so review them before sharing.³

Poly support for .spx

Poly stores, syncs, shares, versions, downloads, and finds .spx files by name. It does not infer a single media type from this ambiguous suffix.

When Speex audio arrives with an accurate audio/ogg classification and can be decoded, Poly can extract supported metadata, transcribe intelligible speech, create audio-similarity data, and open it in the audio player. The Poly agent can use supported audio or its transcript. A Mac report classified as text/xml may receive text preview, indexing, and agent reading. Preserve an accurate content type when importing either kind.

History of .spx

Jean-Marc Valin developed Speex as a patent-free, open speech codec. Xiph.Org's documentation established .spx as its file extension and recommended Ogg for stored Speex bitstreams.²⁴ RFC 5334 formally associated the suffix with Speex-only Ogg audio in September 2008.¹

Speex remains available, but Xiph.Org now calls the codec obsolete and recommends Opus instead.² Apple's System Profiler command has independently used .spx for reopenable XML reports since early versions of Mac OS X, creating the suffix ambiguity.³

Working with .spx and alternatives

Identify the file before converting it. Never send a Mac system report through an audio converter, and avoid repeated lossy transcoding of Speex recordings. Keep the original when preservation or later analysis matters.