MyMediaTools

Convert VOC to M4A — Free Online Tool

Convert VOC audio files — the retro Sound Blaster format used in classic DOS games — to M4A with AAC encoding for modern playback. This tool decodes the raw PCM audio stored in VOC (typically 8-bit unsigned or 16-bit signed PCM) and re-encodes it into AAC inside an MPEG-4 container, making it compatible with iPhones, iTunes, streaming apps, and virtually any modern audio player.

FFmpeg Command

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Estimated output:

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How It Works

VOC files store uncompressed PCM audio in a chunked format developed by Creative Labs, typically at low sample rates (8–22 kHz) and either 8-bit unsigned or 16-bit signed resolution — a relic of early 1990s Sound Blaster hardware. During this conversion, FFmpeg decodes the raw PCM data from the VOC container and re-encodes it using the AAC codec at 128 kbps, wrapping the result in an MPEG-4 (.m4a) container. Because VOC audio is often low-fidelity by modern standards, AAC at 128 kbps will comfortably exceed the source quality ceiling, meaning the output will faithfully represent the original sound without introducing compression artifacts that weren't already present in the source.

What Each Flag Does

Flag What it does
ffmpeg Invokes the FFmpeg command-line tool. In this browser-based tool, the equivalent FFmpeg.wasm (WebAssembly) binary runs entirely in your browser — no server upload occurs. You can use this same command locally on your desktop for files over 1GB.
-i input.voc Specifies the input VOC file. FFmpeg's VOC demuxer reads the chunked Sound Blaster format, parses its block headers (including sample rate and bit-depth metadata), and decodes the raw PCM audio data for re-encoding.
-c:a aac Sets the audio codec to AAC (Advanced Audio Coding) using FFmpeg's built-in AAC encoder. This transcodes the raw PCM audio from the VOC source into compressed AAC, which is the standard audio codec for M4A files and the native format for Apple iTunes and iOS devices.
-b:a 128k Sets the AAC audio bitrate to 128 kilobits per second. This is a strong match for VOC source material, which is typically 8-bit PCM at low sample rates — 128k AAC comfortably exceeds the source quality ceiling without wasting file size on a higher bitrate that the original audio couldn't justify.
-vn Explicitly disables any video stream in the output. This flag is required when writing to an M4A container because M4A is audio-only; without '-vn', FFmpeg may attempt to include a null video stream, which some players and tools cannot handle correctly.
output.m4a Specifies the output filename with the .m4a extension, which tells FFmpeg to use the MPEG-4 audio container. The resulting file contains AAC-encoded audio derived from the original Sound Blaster VOC source, ready for playback in iTunes, Apple Music, VLC, or any modern AAC-compatible audio player.

Common Use Cases

  • Preserving sound effects and music from classic DOS games (e.g., early Sierra, LucasArts, or id Software titles) in a format playable on modern devices without DOSBox
  • Archiving Sound Blaster VOC audio samples from vintage multimedia CD-ROMs into iTunes or Apple Music libraries as M4A files
  • Converting VOC voice lines or sound clips extracted from retro game data files for use in fan projects, remakes, or YouTube video essays
  • Importing old VOC-format audio recordings (from early 1990s PC audio capture software) into modern DAWs or podcast editing tools that support M4A/AAC
  • Creating a mobile-compatible version of a chiptune or tracker module's exported VOC audio for listening on an iPhone or Android device
  • Batch-converting a collection of VOC sound assets from a game modding project into M4A for distribution alongside a modern game engine port

Frequently Asked Questions

No — the M4A output can only be as good as the source VOC file allows. VOC files typically contain 8-bit unsigned PCM at sample rates as low as 8 kHz, which was the standard for early Sound Blaster hardware. AAC encoding at 128 kbps is more than sufficient to faithfully represent that audio, but it cannot recover detail that was never captured. The conversion is essentially a lossless transfer of the original fidelity into a lossy modern container, so you won't notice degradation, but you also won't gain any new clarity.
That characteristic sound is inherent to the VOC source file, not a conversion artifact. VOC audio was designed for Sound Blaster cards in the early 1990s and was often recorded at 8 kHz or 11 kHz with 8-bit resolution — intentionally limited to fit on floppy disks and within the memory constraints of DOS. The M4A file accurately reproduces that original lo-fi character. If you want to improve the perceptual quality, you would need post-processing (e.g., upsampling with noise shaping or EQ) in a DAW after conversion.
No. VOC files can contain internal block-based markers including loop start/end points, silence blocks, and sample rate change blocks — features used by DOS games to create looping sound effects. The M4A/AAC format and the MPEG-4 container have no equivalent mechanism for these DOS-era playback instructions, so they are discarded during conversion. The audio content itself is fully preserved, but any looping or timing metadata embedded in the VOC chunk structure will be lost.
Replace the '128k' value in the '-b:a 128k' flag with your desired bitrate, such as '64k' for a smaller file or '192k' for marginally higher quality. For example: 'ffmpeg -i input.voc -c:a aac -b:a 192k -vn output.m4a'. Keep in mind that because most VOC files contain low-sample-rate 8-bit audio, increasing the bitrate above 128k provides no audible benefit — the source material simply doesn't contain enough detail to justify it.
Yes. On Linux or macOS, you can loop over all VOC files in a directory with: 'for f in *.voc; do ffmpeg -i "$f" -c:a aac -b:a 128k -vn "${f%.voc}.m4a"; done'. On Windows Command Prompt, use: 'for %f in (*.voc) do ffmpeg -i "%f" -c:a aac -b:a 128k -vn "%~nf.m4a"'. This is especially useful when extracting large sets of sound assets from retro game data archives.
Yes — M4A with AAC encoding is Apple's native audio format and is fully supported by iTunes, Apple Music, iOS, and macOS without any plugins. This makes the VOC-to-M4A conversion ideal for adding retro game audio or vintage PC sound clips to your Apple Music library. The MPEG-4 container also supports iTunes metadata fields like track name, artist, and album art, which you can add manually after conversion using iTunes or a tag editor like MusicBrainz Picard.

Technical Notes

VOC is a chunked binary format where audio data is organized into typed blocks, supporting features like looping, silence insertion, and mid-stream sample rate changes — all designed for real-time playback by Sound Blaster DOS drivers. FFmpeg parses these blocks and assembles them into a continuous PCM stream before encoding. The two PCM variants found in VOC files are pcm_u8 (8-bit unsigned, the most common) and pcm_s16le (16-bit signed little-endian, found in later VOC revisions). Both are handled transparently by FFmpeg's VOC demuxer. On the output side, the '-vn' flag is required because M4A is an audio-only container and FFmpeg needs to be explicitly told to suppress any video stream selection attempt. The AAC encoder used here is FFmpeg's native 'aac' codec, which produces spec-compliant LC-AAC output broadly supported across all major platforms. One known limitation: VOC files with multiple audio blocks that change sample rates mid-file may produce unexpected results, as FFmpeg will use the sample rate detected at the start of the file. If your VOC source was recorded at a non-standard rate (e.g., 11,025 Hz or 22,050 Hz), FFmpeg will automatically resample to a standard AAC-compatible rate during encoding.

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