AMR to SPX Converter

Quick AMR to SPX audio transformation online

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Settings

Set the overall output Speex audio bitrate. Designed for human speech encoding, Speex reaches transparency at ultra-low bitrate with a maximum bitrate of 44 kbps.
Set the number of audio channels. This setting is most useful when downmixing channels (e.g., from 5.1 to stereo).
Set the sample rate of the audio. Music with a full spectrum (20 Hz — 20 kHz) requires values not lower than 44.1 kHz to achieve transparency. More info can be found on the wiki.

amr

AMR (Adaptive Multi-Rate) is a compressed audio format optimized for speech, standardized by the European Telecommunications Standards Institute and adopted as a mandatory codec for GSM and 3G mobile networks. The codec dynamically switches between eight bit rates — from 4.75 to 12.2 kbps — depending on network conditions and background noise levels. When link quality drops, the encoder shifts to a lower rate, trading marginal clarity for transmission reliability. This adaptive mechanism is defined by the 3GPP specifications and represents one of the most widely deployed voice codecs globally, used in billions of mobile calls. The primary advantage is compression efficiency: one minute of AMR audio at 12.2 kbps occupies roughly 90 KB, practical for voice memos, voicemail, and MMS on bandwidth-constrained networks. Another benefit is built-in voice activity detection and comfort noise generation, reducing transmission during silence. While AMR is unsuitable for music due to its narrow bandwidth (300-3400 Hz), it excels at delivering intelligible speech under challenging network conditions.
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spx

Speex is an open-source audio codec purpose-built for speech compression, developed by Jean-Marc Valin under the Xiph.Org Foundation. First released in October 2002, it targets voice-over-IP, conferencing, and any scenario where spoken word needs to travel efficiently over a network. SPX files wrap Speex-encoded audio inside an Ogg container, pairing the codec's speech optimization with Ogg's streaming capabilities. Three sampling rates are supported — narrowband at 8 kHz, wideband at 16 kHz, and ultra-wideband at 32 kHz — along with variable bitrate encoding that adapts in real time to speech complexity. A standout advantage is its patent-free, BSD-licensed nature, which allowed developers to embed it freely in both commercial and open-source products. Speex also bundles acoustic echo cancellation, noise suppression, and automatic gain control, features that rival codecs typically delegate to external libraries. Although its creators officially recommend Opus) as a successor since 2012, Speex remains deployed in legacy VoIP systems, archived recordings, and embedded devices where its lightweight decoder footprint is still valued.
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AMR to SPX Made Simple

Upload your AMR audio and get a ready-to-use SPX file in moments — the entire conversion runs in your browser.

Protected Uploads

Every uploaded recording is removed after conversion completes. Converted output is erased within 24 hours automatically.

Browser-Based

Open the converter page, upload, and convert — everything happens in the browser, no desktop app needed.

How to convert AMR to SPX

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose spx or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your spx file right afterwards

About formats

AMR (Adaptive Multi-Rate) is a compressed audio format optimized for speech, standardized by the European Telecommunications Standards Institute and adopted as a mandatory codec for GSM and 3G mobile networks. The codec dynamically switches between eight bit rates — from 4.75 to 12.2 kbps — depending on network conditions and background noise levels. When link quality drops, the encoder shifts to a lower rate, trading marginal clarity for transmission reliability. This adaptive mechanism is defined by the 3GPP specifications and represents one of the most widely deployed voice codecs globally, used in billions of mobile calls. The primary advantage is compression efficiency: one minute of AMR audio at 12.2 kbps occupies roughly 90 KB, practical for voice memos, voicemail, and MMS on bandwidth-constrained networks. Another benefit is built-in voice activity detection and comfort noise generation, reducing transmission during silence. While AMR is unsuitable for music due to its narrow bandwidth (300-3400 Hz), it excels at delivering intelligible speech under challenging network conditions.
Initial release: 1999
Speex is an open-source audio codec purpose-built for speech compression, developed by Jean-Marc Valin under the Xiph.Org Foundation. First released in October 2002, it targets voice-over-IP, conferencing, and any scenario where spoken word needs to travel efficiently over a network. SPX files wrap Speex-encoded audio inside an Ogg container, pairing the codec's speech optimization with Ogg's streaming capabilities. Three sampling rates are supported — narrowband at 8 kHz, wideband at 16 kHz, and ultra-wideband at 32 kHz — along with variable bitrate encoding that adapts in real time to speech complexity. A standout advantage is its patent-free, BSD-licensed nature, which allowed developers to embed it freely in both commercial and open-source products. Speex also bundles acoustic echo cancellation, noise suppression, and automatic gain control, features that rival codecs typically delegate to external libraries. Although its creators officially recommend Opus) as a successor since 2012, Speex remains deployed in legacy VoIP systems, archived recordings, and embedded devices where its lightweight decoder footprint is still valued.
Initial release: October 15, 2002

Frequently Asked Questions

Why convert AMR to SPX?

Speex is optimized for voice encoding — convert AMR to SPX for better speech quality in VoIP and streaming scenarios.

What programs can open SPX files?

VLC, Audacity, and SpeexDec can open and play Speex audio files on all major platforms.

Are there customization options for the SPX output?

The converter lets you tweak audio settings such as bitrate, sample rate, and channels before processing.

Does converting AMR to SPX cost anything?

Basic conversions are available at no charge. Premium plans unlock faster processing and higher file size limits.

Does the conversion from AMR to SPX affect sound quality?

AMR captures limited audio data. Converting to SPX wraps that audio in a better container, but the original quality stays the same.

Can I convert multiple AMR files to SPX at once?

Yes — upload several AMR files simultaneously and convert them all to SPX in a single batch session.

AMR to SPX Quality Rating

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