Convert Standard MIDI File (.midi) to Adaptive Multi-Rate Audio (.amr) online for free. Fast, secure audio conversion with no watermarks or registration.
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MIDI (.midi) is a symbolic music format where each file encodes a complete musical performance as a sequence of machine-readable instructions. The format supports 16 independent channels (channel 10 reserved for percussion per the General MIDI specification), 128 melodic instrument programs, and a rich set of continuous controllers for expressive performance. The .midi extension is the unabbreviated Standard MIDI File designation, commonly encountered in Linux audio workflows and cross-platform music applications.
AMR (Adaptive Multi-Rate) is a speech codec developed by the European Telecommunications Standards Institute (ETSI) specifically for voice communication over GSM cellular networks. It operates at 8 kHz sampling with bitrates from 4.75 to 12.2 kbps. Converting MIDI to AMR is an extreme compression scenario — synthesizing a rich musical performance into a codec designed exclusively for human speech. The result is suitable only for telephony-specific use cases.
IVR (Interactive Voice Response) systems in call centers and automated phone trees frequently require AMR-formatted audio for music-on-hold, menu navigation tones, and branding jingles. MIDI compositions of simple melodies can be rendered to AMR for deployment across telephony infrastructure where no other audio format is supported.
Embedded telephony devices — automotive hands-free systems, elevator intercoms, security intercom panels — often support only AMR decoding hardware. When these systems need melodic alerts or branded audio notifications based on MIDI compositions, AMR is the only viable delivery format despite its severe musical limitations.
FFmpeg decodes the .midi file and synthesizes audio through a SoundFont engine, producing a stereo PCM waveform. This waveform is then drastically processed for AMR compatibility: downmixed from stereo to mono, resampled from the synthesis rate (typically 44.1/48 kHz) to 8 kHz, and low-pass filtered to remove all content above 3.4 kHz. The AMR-NB encoder (libopencore-amrnb) then applies algebraic CELP (Code-Excited Linear Prediction) analysis — a model designed to represent the human vocal tract, not musical instruments — at the selected bitrate. The output is a .amr file with a six-byte AMR header followed by encoded frames.
AMR-NB encoding devastates musical content. The 8 kHz sample rate (3.4 kHz Nyquist limit) eliminates all frequencies above 3400 Hz — meaning cymbals, flutes, violins' upper harmonics, and most of what makes music sound like music is simply gone. The CELP model further distorts the signal because it models excitation patterns optimized for speech formants, not sustained musical tones. Only the simplest monophonic melodies — single-note ringtone-style sequences — produce recognizable musical results. Polyphonic content becomes unintelligible noise.
| Device | MIDI | AMR |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Resolution: N/A
Bitrate: 256 kbps
AAC format required
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
MIDI to AMR serves telephony-only deployments where AMR is the sole supported codec. Limit MIDI content to simple monophonic melodies for any chance of recognizable output.
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| No |
| 기능 | MIDI | AMR |
|---|---|---|
| 전체 이름 | Standard MIDI File | Adaptive Multi-Rate Audio |
| 확장자 | .midi | .amr |
| 최적 용도 | Musical data format | Speech optimized |