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Supported Formats
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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 VOX format and where is it used?
VOX is a low-bitrate audio format using ADPCM compression, developed by Dialogic Corporation for telephony and voice applications. It's used primarily in IVR (Interactive Voice Response) systems - those automated phone menus ('Press 1 for sales, press 2 for support'). VOX provides acceptable voice quality in tiny files, perfect for phone systems with storage constraints.
VOX characteristics: 4-bit ADPCM compression (2:1 reduction from 8-bit), 8kHz or 6kHz sample rate (telephone quality), mono only (single channel), headerless format (raw audio data with no file metadata). This extreme simplicity makes VOX efficient for embedded telephony hardware with minimal processing power and memory.
Should I convert VOX files to WAV or MP3?
Strong reasons to convert VOX:
Telephony-Only Format
VOX designed for phone systems, not general audio. Modern formats more practical for everything else.
Poor Software Support
Most audio players don't recognize VOX. Specialized telephony software only. WAV works everywhere.
Terrible Quality
8kHz, 4-bit ADPCM compression sounds muffled and lo-fi. But converting won't improve it - quality fixed at creation.
No Metadata
VOX has no header or tags. Can't store file information. WAV has proper structure and metadata support.
Convert VOX to WAV for compatibility and editing. Convert to MP3 if you need compressed voice files. VOX is dead-end format.
Does converting VOX to WAV lose quality?
VOX to WAV conversion quality:
Already Lossy
VOX uses 4-bit ADPCM - lossy compression. Converting to WAV doesn't add lost quality. Just changes container.
Telephone Quality
8kHz sample rate = phone call quality. Muffled, no high frequencies. Converting can't improve this fundamental limitation.
No Further Loss
VOX to WAV decodes ADPCM to PCM. No additional compression during conversion. Quality stays same (low).
Headerless Format
VOX lacks file header. Conversion adds proper WAV structure. Audio data identical, format more standard.
Practical Improvement
While audio quality doesn't improve, usability does. WAV files playable everywhere. Worth converting for convenience.
Re-compression Consideration
If converting to MP3, you're compressing already-compressed audio. Use high bitrate (128-192kbps) to minimize additional loss.
Source Quality Limited
VOX was telephone quality by design. Don't expect miracles from conversion. Garbage in, garbage out.
Conversion preserves VOX's limited quality perfectly. You gain compatibility, not audio fidelity. That's the trade-off.
What is ADPCM compression in VOX files?
ADPCM (Adaptive Differential Pulse Code Modulation) encodes the difference between consecutive audio samples rather than absolute values. 'Adaptive' means the algorithm adjusts compression based on audio characteristics. VOX uses 4-bit ADPCM, compressing 8-bit audio to 4-bit (50% size reduction with acceptable quality loss for speech).
Why telephony uses ADPCM: Voice communication tolerates compression artifacts better than music. ADPCM gives 2:1 compression with minimal impact on speech intelligibility. For automated phone systems storing hundreds of voice prompts, halving storage requirements was crucial. Quality degradation was acceptable trade-off.
ADPCM sound quality: Sounds muffled, slightly distorted, compressed - like bad phone connection. Music sounds terrible through ADPCM (artifacts, metallic tones). Speech remains understandable but lacks clarity. This was deliberate design: optimize for voice, sacrifice music quality, minimize file sizes.
Why do VOX files sound so bad?
8kHz sample rate: VOX uses telephone bandwidth (8kHz = frequencies up to 4kHz captured). Human voice is intelligible in this range but sounds muffled. All high-frequency content (sibilance, clarity, air) is missing. It's phone-quality audio by design - enough to understand words, not enough for pleasant listening.
4-bit ADPCM compression: Compressing 8-bit audio to 4-bit adds artifacts - quantization noise, compression 'swooshing,' distortion. For speech it's acceptable (you can understand words), but quality is obviously degraded. Imagine extreme MP3 artifacts but for older compression algorithm.
Purpose-built format: VOX wasn't meant for music or high-fidelity recording. It was designed for 'Press 1 for sales' IVR prompts and voicemail. Terrible quality was intentional trade-off for tiny file sizes on embedded phone systems with kilobytes of storage. Function over form.
Can modern software play VOX files?
Limited support: Audacity can import VOX (may need to specify raw format parameters). VLC doesn't support VOX out of the box. Specialized telephony software (Dialogic tools, IVR authoring software) handles VOX. FFmpeg can convert VOX with proper parameters. But consumer audio players (iTunes, Windows Media Player, phone apps) don't recognize VOX.
The headerless problem: VOX files have no header describing sample rate or format. Software must guess or user must specify parameters (8kHz, mono, 4-bit ADPCM). This makes automatic playback difficult. Proper audio formats have headers with this information - VOX's simplicity is both strength (tiny files) and weakness (compatibility issues).
Recommendation: Don't try to use VOX files directly. Convert to WAV (universal compatibility) or MP3 (compressed but standard). One-time conversion eliminates the compatibility headache. VOX was designed for embedded phone systems, not general-purpose audio playback.
How do I convert VOX to WAV or MP3?
FFmpeg (best method): `ffmpeg -f vox -i input.vox output.wav` converts VOX to WAV. The `-f vox` flag tells FFmpeg to interpret file as VOX format (necessary because VOX has no header). For MP3: `ffmpeg -f vox -i input.vox -codec:a libmp3lame -q:a 4 output.mp3`. FFmpeg handles the headerless format properly.
Audacity (GUI): Import as raw data (File > Import > Raw Data), specify: Dialogic ADPCM encoding, 8000Hz sample rate, 1 channel (mono). Audio appears in editor. Export as WAV or MP3. Works but requires manual parameter specification. Good for single files or if you need to edit audio.
Online converters: Our converter and others support VOX. Upload, convert, download. Easy for occasional conversions. For bulk converting IVR libraries or voicemail archives, FFmpeg with scripting is most efficient despite command-line interface.
What are VOX technical specifications?
Dialogic VOX format specifications:
Sample Rate
6kHz or 8kHz (telephone quality). 8kHz more common. Nyquist theorem limits frequency to half sample rate (4kHz max).
Bit Depth
4-bit ADPCM (compressed from 8-bit). Gives 2:1 compression vs uncompressed 8-bit PCM.
Channels
Mono only (single channel). Telephony doesn't need stereo. Halves file size vs stereo.
File Structure
Headerless - raw ADPCM data only. No metadata, no format information. Extreme simplicity.
Bitrate
32kbps at 8kHz (8000 samples/sec × 4 bits). Tiny bitrate suitable for massive IVR prompt libraries.
VOX specs reflect telephony needs: intelligible speech, minimal storage, simple decoding. Not designed for quality or compatibility.
Is VOX still used in modern phone systems?
Legacy systems only: Old IVR platforms and voicemail systems still use VOX. However, modern VoIP and cloud-based phone systems use better codecs - G.711, G.729, Opus. VOX is legacy format maintained for backward compatibility with ancient Dialogic hardware but not chosen for new deployments.
Why VOX is dying: Better codecs offer superior quality and efficiency. Cloud storage made file size less critical. Modern CPUs handle complex compression easily. VoIP standards (SIP, etc.) use different codecs. VOX was optimized for 1990s-2000s embedded telephony hardware that's now obsolete.
Modern alternatives: For voice: Opus (excellent quality at low bitrates), G.722 (wideband telephony), AAC-LC (good quality, universal). For IVR systems: MP3 (compatibility), WAV (simplicity), or modern streaming codecs. VOX makes no sense for new systems - it's technological debt from previous decade.
Why is VOX format headerless?
Reasons VOX lacks file header:
Embedded System Constraints
1990s IVR hardware had kilobytes of RAM. Every byte mattered. Headers were 'wasted' space. Raw data only.
Simple Hardware Decoding
No header parsing needed. Hardware directly decodes audio stream. Simpler circuitry, lower cost.
Fixed Parameters
Telephony systems used consistent parameters (8kHz, 4-bit ADPCM). Header redundant when parameters always same.
Storage Efficiency
Header-free files slightly smaller. Matters when storing thousands of IVR prompts on limited storage.
Proprietary Ecosystem
VOX used in Dialogic equipment exclusively. Compatibility with other systems not priority. Internal format only.
Drawback Today
Headerless design causes modern compatibility issues. Software can't auto-detect format. Manual configuration needed.
Historical Context
Made sense in resource-constrained embedded systems. Terrible for general-purpose audio. Design reflects telephony-only use.
Modern Comparison
WAV, FLAC, MP3 all have headers. Self-describing files are better. VOX's simplicity is liability now.
Engineering Trade-off
Sacrificed compatibility and metadata for minimal size. Reasonable for 1990s telephony, poor for 2020s audio.
No Modern Justification
Storage is cheap now. CPUs are fast. Headerless format offers no advantages. Pure legacy artifact.
Can I edit VOX files before converting?
Yes, using Audacity: Import VOX as raw data (specify Dialogic ADPCM, 8kHz, mono), audio appears in editor. You can cut silence, normalize volume, remove noise, adjust amplitude. Then export as WAV or MP3. Good for cleaning up old voicemail recordings or IVR prompts before conversion.
Limitations: VOX quality is fundamentally limited (8kHz, 4-bit ADPCM). Editing can't improve quality, only adjust what's there. Noise removal might help marginally. Volume normalization is useful. But don't expect dramatic improvements - source quality is poor.
When to edit: If converting old voicemail or IVR prompts for archival, editing makes sense. Trim silence, normalize volume, remove worst noise. For bulk conversion of telephony files with no sentimental value, skip editing and just batch convert. Time investment depends on content importance.
What's the difference between VOX and VOC formats?
Completely different! VOX is Dialogic telephony format (4-bit ADPCM, 8kHz, headerless, IVR systems). VOC is Creative Labs Sound Blaster format (PCM/ADPCM, various sample rates, with header, DOS gaming). Only similarity is three-letter name starting with 'VO' - formats are unrelated.
VOX = phone systems and voicemail (terrible quality, tiny files, telephony-specific). VOC = DOS game sound effects (better quality, PC gaming, Sound Blaster hardware). Different eras, different purposes, different designs. Don't confuse them!
Software implications: Tools that handle one might not handle the other. VOC has broader retro gaming tool support. VOX needs telephony-specific software or FFmpeg. When converting, make sure you specify correct format to avoid corruption or failure.
How do I batch convert VOX files?
FFmpeg batch - Windows PowerShell: `Get-ChildItem -Filter *.vox | ForEach-Object { ffmpeg -f vox -i $_.Name "$($_.BaseName).wav" }`. Converts all VOX files in folder to WAV. Remember the `-f vox` flag to specify format (VOX is headerless).
FFmpeg batch - Linux/Mac: `for f in *.vox; do ffmpeg -f vox -i "$f" "${f%.vox}.wav"; done`. Bash loop for batch conversion. For MP3 output, add `-codec:a libmp3lame -q:a 4` before output filename.
Tips: VOX files are often named systematically (prompt001.vox, prompt002.vox). Maintain naming in conversion for organization. If converting IVR libraries, group by category (greetings, menus, errors). VOX quality is low - don't use high MP3 bitrates that won't improve anything.
Why do I have VOX files and where did they come from?
Voicemail archives: If you retrieved old voicemail from 1990s-2000s phone systems, messages might be VOX format. Telephony providers often used Dialogic hardware. Corporate phone system backups: Old IVR prompts or call recordings from company phone systems might be VOX.
Telephony development: If you worked with IVR systems, call center software, or phone automation, you may have created VOX files for prompts. Recording software: Some vintage audio recording tools targeting telephony applications saved as VOX format.
Gaming history: Some old games (especially pre-Sound Blaster era) used VOX for voice samples due to small file size. Rare but possible. Most likely source: telephony-related activities or archived phone system content.
Should I keep VOX files or convert everything?
For general use: Convert to WAV or MP3 immediately and delete VOX originals. They're telephony-specific format with terrible compatibility. Converted files are infinitely more practical. VOX offers nothing useful for modern audio workflows.
For archives with historical value: If VOX files are old voicemail from deceased loved ones, IVR prompts from defunct company, or historical telephony recordings, keep originals AND create conversions. Original VOX preserves authentic format, conversions enable actual playback.
Recommendation: VOX format is dead end with no future. Converting ensures long-term accessibility. Storage is cheap - if files have any value, keep originals for historical accuracy but prioritize usable conversions. Don't let obsolete formats trap important content.