Convert RMI to AAC — Free Online Converter
Convert RIFF MIDI (.rmi) to Advanced Audio Coding (.aac) online for free. Fast, secure audio conversion with no watermarks or registration....
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How to Convert
Upload your .rmi file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .aac file when it's ready.
About RMI to AAC Conversion
RMI (RIFF MIDI) encapsulates Standard MIDI File data within a RIFF container, the foundational binary structure Microsoft developed for Windows multimedia. The RIFF wrapper provides structured metadata storage through INFO sub-chunks — INAM (title), IART (artist), ICOP (copyright), ICMT (comments) — capabilities that raw .mid files lack entirely. RMI was the default MIDI format for Windows applications using the Multimedia Control Interface (MCI) and remained prevalent through the Windows XP era.
AAC (Advanced Audio Coding) is the dominant lossy audio codec powering Apple Music, YouTube, and virtually every modern streaming platform. Converting RMI to AAC strips the RIFF envelope, synthesizes the enclosed MIDI data through a software synthesizer, and encodes the rendered waveform as AAC. The result is a universally playable audio file derived from Windows-native MIDI content.
Why Convert RMI to AAC?
RMI files exist almost exclusively within Windows multimedia archives — corporate training modules built with Windows MCI, DirectX-era game assets, and educational software from the late 1990s. These files cannot be played on macOS, Linux, iOS, or Android without first extracting the MIDI data from the RIFF container. AAC conversion creates a universally compatible audio rendering.
AAC offers superior compression efficiency compared to MP3, making it the optimal lossy format for distributing rendered MIDI content. At 128 kbps, AAC delivers quality that rivals MP3 at 192 kbps. For organizations digitizing legacy Windows multimedia libraries, AAC provides the best balance of file size, audio quality, and universal device support.
Common Use Cases
- Digitizing corporate training module audio from Windows MCI RMI files to AAC for modern LMS platforms
- Converting DirectX game soundtrack RMI assets to AAC for retro game music collections
- Extracting and rendering RMI audio from legacy Windows educational software for web distribution
- Migrating Windows kiosk background music from RMI to AAC for cross-platform digital signage
- Archiving Windows CE device notification sounds as universally playable AAC files
How It Works
FFmpeg identifies the RIFF container by its 'RIFF' four-character code and 'RMID' form type, then extracts the embedded MIDI data chunk. The MIDI event stream is fed to a software synthesizer that maps General MIDI program numbers to SoundFont instrument patches, processes note-on/off events with velocity-scaled amplitude, and applies controller messages (volume, pan, expression, sustain pedal). The rendered stereo PCM is encoded using AAC-LC via FFmpeg's native encoder or libfdk_aac, then packaged in an M4A container with proper iTunes-compatible metadata atoms.
Quality & Performance
At 192-256 kbps AAC-LC, encoding artifacts are imperceptible for synthesized MIDI content. The quality ceiling is entirely determined by the SoundFont — a professional multi-sampled bank produces rich, expressive audio, while the default General MIDI set sounds characteristically synthetic. RMI files designed for the Microsoft GS Wavetable Synth may sound noticeably different when rendered through a third-party SoundFont, as instrument voicing and reverb characteristics differ between synthesis engines.
Device Compatibility
| Device | RMI | AAC |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Native |
| iPhone/iPad | Partial | Native |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No | No |
Recommended Settings by Platform
Spotify
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Apple Music
Resolution: N/A
Bitrate: 256 kbps
AAC format required
SoundCloud
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Podcast
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
Tips for Best Results
- 1Use 192 kbps AAC-LC for optimal quality-to-size ratio — synthesized MIDI content does not benefit from higher bitrates
- 2Compare the AAC output against playback from Windows Media Player to assess whether the SoundFont choice faithfully represents the original RMI sound
- 3Transfer RIFF INFO metadata (title, artist, copyright) manually to AAC/M4A tags after conversion to preserve attribution
- 4Use libfdk_aac encoder if available — it produces marginally better quality than FFmpeg's native AAC encoder at equivalent bitrates
- 5Batch convert entire RMI collections at once since the synthesis step is CPU-intensive and benefits from sequential processing to avoid memory contention
RMI to AAC transforms Windows-specific RIFF MIDI content into the most widely supported lossy audio format. Prioritize SoundFont selection to match the original Windows playback character.