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Supported Formats
Convert between all major file formats with high quality
Common Formats
MPEG-1 Audio Layer III - the most universal audio format worldwide, using lossy compression to reduce file sizes by 90% while maintaining excellent perceived quality. Perfect for music libraries, podcasts, portable devices, and any scenario requiring broad compatibility. Supports bitrates from 32-320kbps. Standard for digital music since 1993, playable on virtually every device and platform.
Waveform Audio File Format - uncompressed PCM audio providing perfect quality preservation. Standard Windows audio format with universal compatibility. Large file sizes (10MB per minute of stereo CD-quality). Perfect for audio production, professional recording, mastering, and situations requiring zero quality loss. Supports various bit depths (16, 24, 32-bit) and sample rates. Industry standard for professional audio work.
Ogg Vorbis - open-source lossy audio codec offering quality comparable to MP3/AAC at similar bitrates. Free from patents and licensing restrictions. Smaller file sizes than MP3 at equivalent quality. Used in gaming, open-source software, and streaming. Supports variable bitrate (VBR) for optimal quality. Perfect for applications requiring free codecs and good quality. Growing support in media players and platforms.
Advanced Audio Coding - successor to MP3 offering better quality at same bitrate (or same quality at lower bitrate). Standard audio codec for Apple devices, YouTube, and many streaming services. Supports up to 48 channels and 96kHz sample rate. Improved frequency response and handling of complex audio. Perfect for iTunes, iOS devices, video streaming, and modern audio applications. Part of MPEG-4 standard widely supported across platforms.
Free Lossless Audio Codec - compresses audio 40-60% without any quality loss. Perfect bit-for-bit preservation of original audio. Open-source format with no patents or licensing fees. Supports high-resolution audio (192kHz/24-bit). Perfect for archiving music collections, audiophile listening, and scenarios where quality is paramount. Widely supported by media players and streaming services. Ideal balance between quality and file size.
MPEG-4 Audio - AAC or ALAC audio in MP4 container. Standard audio format for Apple ecosystem (iTunes, iPhone, iPad). Supports both lossy (AAC) and lossless (ALAC) compression. Better quality than MP3 at same file size. Includes metadata support for artwork, lyrics, and rich tags. Perfect for iTunes library, iOS devices, and Apple software. Widely compatible across platforms despite Apple association. Common format for purchased music and audiobooks.
Windows Media Audio - Microsoft's proprietary audio codec with good compression and quality. Standard Windows audio format with native OS support. Supports DRM for protected content. Various profiles (WMA Standard, WMA Pro, WMA Lossless). Comparable quality to AAC at similar bitrates. Perfect for Windows ecosystem and legacy Windows Media Player. Being superseded by AAC and other formats. Still encountered in Windows-centric environments and older audio collections.
Lossless Formats
Apple Lossless Audio Codec - Apple's lossless compression reducing file size 40-60% with zero quality loss. Perfect preservation of original audio like FLAC but in Apple ecosystem. Standard lossless format for iTunes and iOS. Supports high-resolution audio up to 384kHz/32-bit. Smaller than uncompressed but larger than lossy formats. Perfect for iTunes library, audiophile iOS listening, and maintaining perfect quality in Apple ecosystem. Comparable to FLAC but with better Apple integration.
Monkey's Audio - high-efficiency lossless compression achieving better ratios than FLAC (typically 55-60% of original). Perfect quality preservation with zero loss. Free format with open specification. Slower compression/decompression than FLAC. Popular in audiophile communities. Limited player support compared to FLAC. Perfect for archiving when maximum space savings desired while maintaining perfect quality. Best for scenarios where storage space is critical and processing speed is not.
WavPack - hybrid lossless/lossy audio codec with unique correction file feature. Can create lossy file with separate correction file for lossless reconstruction. Excellent compression efficiency. Perfect for flexible audio archiving. Less common than FLAC. Supports high-resolution audio and DSD. Convert to FLAC for universal compatibility.
True Audio - lossless audio compression with fast encoding/decoding. Similar compression to FLAC with simpler algorithm. Open-source and free format. Perfect quality preservation. Less common than FLAC with limited player support. Perfect for audio archiving when FLAC compatibility not required. Convert to FLAC for broader compatibility.
Audio Interchange File Format - Apple's uncompressed audio format, equivalent to WAV but for Mac. Stores PCM audio with perfect quality. Standard audio format for macOS and professional Mac audio applications. Supports metadata tags better than WAV. Large file sizes like WAV (10MB per minute). Perfect for Mac-based audio production, professional recording, and scenarios requiring uncompressed audio on Apple platforms. Interchangeable with WAV for most purposes.
Modern Formats
Opus Audio Codec - modern open-source codec (2012) offering best quality at all bitrates from 6kbps to 510kbps. Excels at both speech and music. Lowest latency of modern codecs making it perfect for VoIP and real-time communication. Superior to MP3, AAC, and Vorbis at equivalent bitrates. Used by WhatsApp, Discord, and WebRTC. Ideal for streaming, voice calls, podcasts, and music. Becoming the universal audio codec for internet audio.
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Matroska Audio - audio-only Matroska container supporting any audio codec. Flexible format with metadata support. Can contain multiple audio tracks. Perfect for audio albums with chapters and metadata. Part of Matroska multimedia framework. Used for audiobooks and multi-track audio. Convert to FLAC or MP3 for universal compatibility.
Legacy Formats
MPEG-1 Audio Layer II - predecessor to MP3 used in broadcasting and DVDs. Better quality than MP3 at high bitrates. Standard audio codec for DVB (digital TV) and DVD-Video. Lower compression efficiency than MP3. Perfect for broadcast applications and DVD authoring. Legacy format being replaced by AAC in modern broadcasting. Still encountered in digital TV and video production workflows.
Dolby Digital (AC-3) - surround sound audio codec for DVD, Blu-ray, and digital broadcasting. Supports up to 5.1 channels. Standard audio format for DVDs and HDTV. Good compression with multichannel support. Perfect for home theater and video production. Used in cinema and broadcast. Requires Dolby license for encoding.
Adaptive Multi-Rate - speech codec optimized for mobile voice calls. Excellent voice quality at very low bitrates (4.75-12.2 kbps). Standard for GSM and 3G phone calls. Designed specifically for speech, not music. Perfect for voice recordings, voicemail, and speech applications. Used in WhatsApp voice messages and mobile voice recording. Efficient for voice but inadequate for music.
Sun/NeXT Audio - simple audio format from Sun Microsystems and NeXT Computer. Uncompressed or μ-law/A-law compressed audio. Common on Unix systems. Simple header with audio data. Perfect for Unix audio applications and legacy system compatibility. Found in system sounds and Unix audio files. Convert to WAV or MP3 for modern use.
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RealAudio - legacy streaming audio format from RealNetworks (1990s-2000s). Pioneered internet audio streaming with low-bitrate compression. Obsolete format replaced by modern streaming technologies. Poor quality by today's standards. Convert to MP3 or AAC for modern use. Historical importance in early internet audio streaming.
Specialized Formats
DTS Coherent Acoustics - surround sound codec competing with Dolby Digital. Higher bitrates than AC-3 with potentially better quality. Used in DVD, Blu-ray, and cinema. Supports up to 7.1 channels and object-based audio. Perfect for high-quality home theater. Premium audio format for video distribution. Convert to AC-3 or AAC for broader compatibility.
Core Audio Format - Apple's container for audio data on iOS and macOS. Supports any audio codec and unlimited file sizes. Modern replacement for AIFF on Apple platforms. Perfect for iOS app development and professional Mac audio. No size limitations (unlike WAV). Can store multiple audio streams. Convert to M4A or MP3 for broader compatibility outside Apple ecosystem.
VOC (Creative Voice File) - audio format from Creative Labs Sound Blaster cards. Popular in DOS era (1989-1995) for games and multimedia. Supports multiple compression formats and blocks. Legacy PC audio format. Common in retro gaming. Convert to WAV or MP3 for modern use. Important for DOS game audio preservation.
Speex - open-source speech codec designed for VoIP and internet audio streaming. Variable bitrate from 2-44 kbps. Optimized for speech with low latency. Better than MP3 for voice at low bitrates. Being superseded by Opus. Perfect for voice chat, VoIP, and speech podcasts. Legacy format replaced by Opus in modern applications.
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How to Convert Files
Upload your files, select output format, and download converted files instantly. Our converter supports batch conversion and maintains high quality.
Frequently Asked Questions
What is Speex and why was it created?
Speex is an open-source audio codec designed specifically for speech compression, developed by Jean-Marc Valin and released in 2003. It was created to provide patent-free, high-quality voice compression for VoIP (Voice over IP) applications. Speex offers variable bitrate (2.15kbps to 44kbps), multiple quality modes, and acoustic echo cancellation - optimized for internet telephony.
Design goals: Low bitrate voice quality better than GSM, patent-free licensing (no royalties), variable bitrate for network adaptation, low CPU requirements for real-time communication, and acoustic echo cancellation built-in. Speex succeeded in VoIP market, used by Skype, Mumble, TeamSpeak, and many softphones in 2000s.
Should I convert Speex to MP3 or Opus?
Convert Speex for better compatibility:
Obsolete Format
Speex replaced by Opus (2012). Modern software support declining. Convert to standard formats for future access.
Limited Playback
Most media players don't support Speex. VLC does, but mobile/portable support is poor. MP3 works everywhere.
Better Modern Options
Opus (Speex successor) sounds better at all bitrates. If staying with open codec, Opus is superior choice.
Universal Compatibility
MP3 64-96kbps gives good voice quality with maximum device compatibility. Safe archival choice.
Convert Speex to MP3 for compatibility or Opus for modern open-source alternative. Don't maintain Speex archives long-term.
Does converting Speex to MP3 lose quality?
Speex conversion quality considerations:
Lossy to Lossy
Both Speex and MP3 are lossy. Transcoding always loses quality. But for voice, high bitrate MP3 preserves acceptable quality.
Bitrate Matching
Speex typically 8-24kbps for speech. Converting to 96kbps MP3 provides headroom, minimizes additional loss.
Speech Optimization
Speex optimized for speech, MP3 optimized for music. MP3 at 96kbps handles voice well despite different design.
Acceptable Trade-off
Some quality loss from transcoding, but universal MP3 compatibility outweighs marginal degradation for voice.
Use High Bitrate
Convert Speex to 96-128kbps MP3. Higher target bitrate minimizes generation loss from lossy-to-lossy conversion.
Practical Reality
Speex recordings are voice memos, podcasts, VoIP calls - not music. Slight quality loss acceptable for utility.
Better Than Nothing
Keeping Speex files means decreasing playback options. MP3 conversion preserves accessibility long-term.
Yes, converting loses quality. But Speex file you can't play is worse than MP3 file you can. Choose accessibility.
What software can play Speex files?
Desktop: VLC (Windows/Mac/Linux - best option), foobar2000 (Windows with plugins), Audacity (import for editing), and VoIP applications that created them (Mumble, TeamSpeak, etc.). General media players like Windows Media Player and iTunes don't support Speex natively.
Mobile: Very limited support. Some Android apps might handle Speex, iOS has virtually no support. VLC Mobile works but isn't ideal for voice recordings. Speex was designed for real-time VoIP, not file playback - software support reflects this.
Best practice: Don't rely on Speex playback. Use VLC for occasional listening, but convert files to MP3/AAC for regular use and archival. Fighting software compatibility isn't worth it for obsolete codec. Convert once, play anywhere.
How do I convert Speex to MP3?
FFmpeg (command line): `ffmpeg -i input.spx -codec:a libmp3lame -b:a 96k output.mp3` converts with appropriate voice bitrate. FFmpeg handles Speex despite format obscurity. Reliable, fast, cross-platform.
Audacity (GUI): Import Speex file (File > Open), then export as MP3 (File > Export > Export as MP3). Set bitrate to 96-128kbps for voice. Simple interface for occasional conversions. Audacity's Speex support works well.
Online converters: Our converter and others support Speex. Upload .spx file, select MP3 output, choose 96kbps bitrate, download. Easy for single files. For batch conversion of archived VoIP recordings, FFmpeg scripting is more efficient.
What's the difference between Speex and Opus?
Opus is Speex's successor from same organization (Xiph.Org). Opus launched 2012, incorporating lessons from Speex development plus CELT codec. Opus sounds significantly better than Speex at all bitrates - 24kbps Opus beats 32kbps Speex easily. Also more versatile, handling both speech and music well.
Technical improvements: Opus has lower latency (crucial for VoIP), wider range (6kHz to 20kHz audio bandwidth vs Speex's narrowband/wideband modes), better packet loss concealment, more efficient compression, and can handle both voice and music (Speex is speech-only).
Current status: Xiph.Org officially recommends Opus over Speex. Speex is maintained for legacy compatibility but no new features. All modern applications should use Opus - it's better in every measurable way. Speex is historical stepping stone to Opus.
Can Speex be used for music?
Technically yes, practically no. Speex is speech codec - its psychoacoustic model, compression algorithms, and optimization targets speech characteristics. Music through Speex sounds muffled, compressed, lacking detail and dynamics. Quality is poor even at maximum Speex bitrates.
Why it fails: Speech has different spectral characteristics than music. Speex's codec design exploits speech patterns (formants, pitch periods, pauses) which don't exist in music. The efficiency gains for speech become quality losses for music. It's wrong tool for the job.
Alternatives: For low-bitrate music use MP3 (128kbps minimum), AAC (96kbps+), or Opus (96-128kbps for music). Opus is particularly good - it's Speex's successor and handles both speech AND music well. Never use Speex for music - it will sound terrible.
What bitrates does Speex support?
Speex bitrate modes:
Narrowband (8kHz)
2.15-24.6kbps. Telephone quality. Good for basic voice, acceptable intelligibility, limited fidelity.
Wideband (16kHz)
4-42.2kbps. Better voice quality. More natural sound, good for VoIP. Most common Speex mode.
Ultra-wideband (32kHz)
8-44.2kbps. Highest Speex quality. Rarely used - Opus better at these rates anyway.
Variable Bitrate
Speex supports VBR - adjusts bitrate based on audio complexity. More efficient than constant bitrate.
Quality vs Bitrate
Higher bitrate = better quality, larger files. 16kbps wideband good balance for voice. 24kbps excellent.
Most Speex files use 8-24kbps wideband mode for VoIP. Convert to 96kbps MP3 for good archival quality.
Why is Speex better than GSM but worse than Opus?
Speex vs GSM: Speex is much better - variable bitrate (GSM is fixed 13kbps), wideband support (GSM is narrowband 8kHz only), patent-free (GSM had patent issues), and better quality at equivalent bitrates. Speex was major improvement over 1990s codecs like GSM.
Opus vs Speex: Opus is better in every way - lower latency, better quality at all bitrates, wider audio bandwidth (6Hz-20kHz full-band), handles music AND speech, more efficient compression, better packet loss recovery. Opus represents 10+ years of additional codec research.
Evolution: GSM (1991) → Speex (2003) → Opus (2012). Each generation improved significantly. Speex was excellent for its time, advancing VoIP quality substantially. But Opus is state-of-art now. Speex served its purpose and was succeeded by better technology.
How do I batch convert Speex files?
Batch Speex conversion methods:
FFmpeg (Windows)
`for %f in (*.spx) do ffmpeg -i "%f" -codec:a libmp3lame -b:a 96k "%~nf.mp3"` converts folder.
FFmpeg (Linux/Mac)
`for f in *.spx; do ffmpeg -i "$f" -b:a 96k "${f%.spx}.mp3"; done` bash script.
Audacity Macros
Create batch processing macro. Import Speex, export MP3, repeat. GUI-friendly but slower.
Bitrate Selection
96kbps MP3 good for voice archives. 128kbps if you want safety margin. Don't use 320kbps - wasteful.
Preserve Structure
Maintain folder organization during batch conversion. Keep voice recordings organized logically.
Verify Sample
Test one conversion before processing hundreds. Ensure MP3 quality acceptable for your voice recordings.
Metadata Handling
Speex files may have minimal metadata. Add dates, descriptions to converted MP3s for organization.
Backup Strategy
Keep Speex originals until MP3 conversion verified. Delete originals after confirming successful conversion.
Long-term Access
Converting Speex to MP3 ensures you can play recordings years from now. Future-proofing archives.
Simple Process
Speex conversion is straightforward. FFmpeg handles it well. Don't overthink - just convert and gain compatibility.
Where was Speex commonly used?
VoIP applications: Skype (early versions), Mumble (gaming voice chat), TeamSpeak (gaming communication), Asterisk PBX, FreeSWITCH (telephony platforms), Google Talk (early version), and countless softphones. Speex was THE open-source VoIP codec in 2000s before Opus existed.
Gaming: Many online games used Speex for voice chat. Low latency and low bitrate made it perfect for in-game communication. Games needed patent-free codec that wouldn't add licensing costs. Speex filled this need perfectly.
Podcasting/recording: Some early podcasting software and voice recording apps used Speex for efficient storage. However, MP3 remained more popular for podcast distribution. Speex was more niche in podcasting than in real-time VoIP.
Can Speex files be edited?
Yes, but awkwardly. Audacity can import Speex files, allowing editing (cut, trim, effects), then export to Speex or other formats. However, editing lossy audio (including Speex) compounds quality loss. For critical editing, work with lossless formats.
Better workflow: Convert Speex to WAV (uncompressed), edit in WAV domain (lossless editing), then export final to MP3/AAC/Opus as needed. This minimizes generation loss - only one lossy encoding step at end instead of multiple decode/edit/encode cycles.
Practical advice: For simple edits (trimming silence, adjusting volume), editing Speex directly in Audacity is fine. For complex editing or multiple operations, convert to lossless first. Quality loss from extra encoding cycle might not matter for voice memos but does matter for important recordings.
Is Speex royalty-free?
Yes, completely! Speex is BSD-licensed (very permissive open-source license). No patents, no royalties, no licensing fees. You can use Speex in commercial products, open-source projects, or personal applications without paying anyone. This was major advantage over proprietary codecs.
Why it mattered: In 2000s, many audio codecs had patent issues and licensing costs (MP3, AAC, others). Speex provided patent-free voice compression for VoIP without legal concerns or per-unit royalties. This enabled wide adoption in open-source and commercial VoIP applications.
Current alternative: Opus (Speex's successor) is also completely royalty-free and patent-free. Xiph.Org Foundation ensured both codecs remain free for all uses. For new projects needing free voice/audio codec, use Opus - better quality and still completely free.
What happened to Speex development?
Speex development essentially stopped when Opus development began (2007-2012). Xiph.Org Foundation created Opus as next-generation codec incorporating Speex's speech compression plus CELT's music capabilities. Opus achieved everything Speex did but better, making continued Speex development unnecessary.
Current status: Speex is in maintenance mode - bug fixes only, no new features. It works fine for legacy applications but shouldn't be chosen for new projects. Xiph.Org explicitly recommends Opus for all new development. Speex served its purpose (advancing open-source VoIP 2003-2012), then was superseded.
Lessons learned: Speex demonstrated successful open-source audio codec development and proved patent-free codecs could compete with proprietary alternatives. This experience directly informed Opus design. Speex is success story - it achieved goals, advanced technology, then handed torch to better successor.
Speex vs MP3 vs Opus - which for voice recordings?
Don't use Speex: It's obsolete with declining software support. Even for voice (its specialty), better options exist. Only reason to work with Speex is converting old files. Never create new Speex files.
Use MP3 for maximum compatibility: 96-128kbps MP3 gives good voice quality with universal playback. Every device, player, and platform supports MP3. Safe choice for voice recordings you want accessible forever. Old-fashioned but reliable.
Use Opus for modern efficiency: 24-32kbps Opus gives excellent voice quality in tiny files. Better than Speex at lower bitrate. Perfect for modern voice recording apps, podcasts, or VoIP. For voice: Opus 24-48kbps (best quality/size, modern), MP3 96kbps (maximum compatibility, universal), AAC 64-96kbps (good balance, efficient). Never Speex (obsolete, replaced by Opus).