Convert MKV to AMR — Free Online Converter
Convert Matroska Video (.mkv) to Adaptive Multi-Rate Audio (.amr) online for free. Fast, secure video conversion with no watermarks or registration....
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Upload your .mkv 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 .amr file when it's ready.
About MKV to AMR Conversion
AMR (Adaptive Multi-Rate) is a narrowband speech codec designed for GSM cellular networks, operating at extremely low bitrates between 4.75 and 12.2 kbps. Converting MKV to AMR makes sense only when you need voice audio for legacy telecom systems, embedded devices, or applications that specifically require AMR input.
Why Convert MKV to AMR?
AMR was standardized by 3GPP specifically for encoding human speech over cellular networks, and it remains embedded in VoIP gateways, IVR phone systems, and telecom testing equipment. Some legacy Android voicemail apps and older Nokia handsets store and play recordings exclusively in AMR format, so converting MKV audio to AMR may be required for compatibility with these systems.
The format's extremely low bitrate also makes it useful for scenarios where bandwidth is severely limited. A one-minute AMR file at 12.2 kbps occupies only about 90 KB, compared to roughly 1 MB for MP3 at 128 kbps. For automated phone systems that store thousands of hours of voice prompts or call recordings, AMR's compact size keeps storage costs manageable.
Common Use Cases
- Creating voice prompts for IVR (Interactive Voice Response) telephone systems
- Preparing audio for legacy VoIP gateways that only accept AMR input
- Extracting dialogue from MKV training videos for use in telecom compliance archives
- Converting recorded lectures to AMR for distribution via SMS/MMS on 2G networks
- Generating test files for AMR codec development and quality benchmarking
How It Works
FFmpeg decodes the MKV's audio track and re-encodes it using the libopencore-amrnb encoder. The output is forced to mono at 8 kHz sample rate, which are the only parameters AMR-NB supports. The encoder operates at one of eight fixed bitrates from 4.75 to 12.2 kbps. Any stereo, surround, or high-sample-rate audio in the MKV is downmixed and resampled to fit AMR's constraints.
Quality & Performance
AMR was designed for intelligible speech, not music. Voice recordings remain clear and understandable at 12.2 kbps, but music, environmental sounds, and complex audio will sound heavily compressed with audible artifacts. The 8 kHz sampling rate means all frequencies above 4 kHz are lost. This is a purpose-built speech codec, and quality expectations should be set accordingly.
Device Compatibility
| Device | MKV | AMR |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No | No |
Recommended Settings by Platform
YouTube
Resolution: 1920x1080
Bitrate: 8-12 Mbps
H.264 recommended for fast processing
Resolution: 1080x1080
Bitrate: 3.5 Mbps
Square or 9:16 for Reels
TikTok
Resolution: 1080x1920
Bitrate: 4 Mbps
9:16 vertical, under 60s ideal
Twitter/X
Resolution: 1280x720
Bitrate: 5 Mbps
Under 140s, 512MB max
Resolution: 960x540
Bitrate: 2 Mbps
16MB limit for standard, 64MB for document
Discord
Resolution: 1280x720
Bitrate: 4 Mbps
8MB free, 50MB Nitro
Tips for Best Results
- 1Always use the highest bitrate (12.2 kbps) unless your target system specifically requires a lower mode for bandwidth reasons
- 2Pre-process the audio with a noise gate or noise reduction filter if the MKV source has background noise, since AMR amplifies ambient sounds
- 3If the MKV has multiple audio tracks, verify you are extracting the correct one — commentary tracks will produce different AMR output than the main dialogue
- 4Test AMR playback on the target telecom device or system before converting a large batch, as some systems expect specific AMR modes
- 5Consider AMR-WB (.awb) if the target system supports it, as the wideband codec at 23.85 kbps sounds dramatically better than AMR-NB
Related Conversions
MKV to AMR is a specialized conversion for telecom, embedded systems, and ultra-low-bandwidth scenarios where speech intelligibility matters more than audio fidelity.