MP2 vs SPX
A detailed comparison of MPEG Layer 2 Audio and Speex Audio — file size, quality, compatibility, and which format to choose for your workflow.
MPEG Layer 2 Audio
Audio FilesMP2 (MPEG-1 Audio Layer II) is an audio compression standard that preceded MP3. It remains the standard audio format for digital radio broadcasting (DAB) and digital television (DVB) due to its lower encoding delay and better error resilience.
About MP2 filesSpeex Audio
Audio FilesSpeex is an open-source audio compression format specifically designed for speech encoding. It uses Code-Excited Linear Prediction (CELP) and supports narrowband, wideband, and ultra-wideband modes for different speech quality requirements.
About SPX filesStrengths Comparison
MP2 Strengths
- Robust against transmission errors — designed for broadcast.
- Lower CPU demand than MP3 — mattered for 1990s receivers.
- Universal playback via every audio player.
- ~30 years of broadcast field experience.
SPX Strengths
- Patent-free voice codec.
- Three sample-rate modes for voice.
- Low CPU decode.
Limitations
MP2 Limitations
- Worse compression than MP3 at the same quality.
- Largely obsolete for new content.
- Patent licensing never fully cleared (though most expired by 2017).
- Consumer ecosystems chose MP3 and never came back.
SPX Limitations
- Deprecated in favor of Opus.
- No music support.
- Rarely used in new projects.
Technical Specifications
| Specification | MP2 | SPX |
|---|---|---|
| MIME type | audio/mpeg | audio/speex |
| Extensions | .mp2, .m2a, .mpa | — |
| Standard | ISO/IEC 11172-3 Layer II | — |
| Sample rates | 16, 22.05, 24, 32, 44.1, 48 kHz | — |
| Bitrates | 32-384 kbps | — |
| Extension | — | .spx |
| Container | — | Ogg |
| Modes | — | Narrowband/Wideband/Ultra-wideband |
| Successor | — | Opus |
Typical File Sizes
MP2
- DAB radio stream (128 kbps) 1 MB/min
- DVD audio track (192 kbps) 1.4 MB/min
- 3-min song at 192 kbps 4.3 MB
SPX
- 1 min voice (wideband 24 kbps) ~180 KB
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Frequently Asked Questions
MP2 (MPEG Layer 2 Audio) is an audio file format used to store sound recordings — music, voice, podcasts, sound effects. The format defines how the audio samples are compressed (or stored raw), what bitrates are supported, and how metadata such as title, artist, album, and cover art is embedded. It is part of the audio files family.
SPX (Speex Audio) is an audio file format used to store sound recordings — music, voice, podcasts, sound effects. The format defines how the audio samples are compressed (or stored raw), what bitrates are supported, and how metadata such as title, artist, album, and cover art is embedded. It is part of the audio files family.
VLC, foobar2000, and the default media players on Windows and macOS handle MP2 natively. On mobile, iOS Music and Android media apps vary in their support — popular formats work everywhere; niche ones may need a dedicated app. If playback fails on a device, converting to MP3 or AAC usually solves it.
VLC, foobar2000, and the default media players on Windows and macOS handle SPX natively. On mobile, iOS Music and Android media apps vary in their support — popular formats work everywhere; niche ones may need a dedicated app. If playback fails on a device, converting to MP3 or AAC usually solves it.
Upload the MP2 to KaijuConverter and pick MP3, WAV, FLAC, AAC, OGG, or any other target. Our FFmpeg pipeline decodes the audio and re-encodes to the target format at sensible default bitrates (VBR ~190 kbps for music, 96 kbps for speech). Metadata and cover art travel with the audio where both formats support them.
MP2 can be lossy or lossless depending on the specific variant. Lossy variants (smaller files) discard some audio detail during compression in ways tuned to be inaudible; lossless variants preserve every sample exactly but produce larger files. For distribution, lossy at high bitrate is standard; for archival, lossless wins.