Extract Audio from RMVB to AMR — Free Online Tool
Extract audio from RMVB video files and convert it to AMR format, optimized for speech and mobile telephony applications. This tool decodes the AAC or MP3 audio stream embedded in your RealMedia variable bitrate container and re-encodes it using the libopencore_amrnb codec at 12.2 kbps — the highest quality AMR-NB bitrate — making it ideal for voice content extraction from older RealMedia recordings.
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FFmpeg Command
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Estimated output:
Conversion Complete!
DownloadHow It Works
RMVB files store audio as AAC or MP3 streams inside the RealMedia container. This conversion first demuxes the RMVB container to extract the audio stream, then fully decodes it to raw PCM audio. That decoded audio is then re-encoded using the libopencore_amrnb encoder into AMR Narrowband format. AMR-NB is a speech-optimized codec that only supports 8 kHz sample rate and mono audio, so FFmpeg automatically downmixes any stereo audio and resamples it to 8 kHz during encoding. The video stream is completely discarded with the -vn flag. Because AMR is narrowband and speech-focused, music or wideband audio content from RMVB files will sound noticeably degraded — this codec is purpose-built for voice intelligibility, not fidelity.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg application, the open-source multimedia processing engine that handles demuxing the RMVB container, decoding the audio stream, and re-encoding it to AMR-NB. |
-i input.rmvb
|
Specifies the input RMVB file. FFmpeg uses its RealMedia demuxer to parse the variable-bitrate container and expose the embedded audio stream (typically AAC or MP3) for processing. |
-vn
|
Disables video output entirely, instructing FFmpeg to ignore the video stream from the RMVB file. Since AMR is an audio-only format, no video data is written to the output. |
-c:a libopencore_amrnb
|
Selects the libopencore_amrnb encoder to produce AMR Narrowband audio, the standard codec for .amr files used in mobile telephony. This re-encodes the decoded RMVB audio stream at 8 kHz mono, optimized for speech intelligibility. |
-b:a 12200
|
Sets the AMR-NB bitrate to 12,200 bits per second (12.2 kbps), which corresponds to the highest quality codec mode in the AMR-NB standard. This gives the best possible voice clarity within the narrowband AMR format's constraints. |
output.amr
|
Defines the output filename with the .amr extension, which tells FFmpeg to write an AMR-NB file. The .amr container is widely recognized by mobile devices, voicemail systems, and telephony applications. |
Common Use Cases
- Extracting spoken dialogue or voice narration from old RealMedia educational lectures or e-learning recordings for playback on feature phones or embedded voice systems
- Converting RMVB-archived conference call recordings or interviews into AMR for storage in telecom systems that natively handle AMR voice files
- Pulling the audio commentary track from a RealMedia sports or news broadcast to create a compact, speech-optimized voice clip for mobile distribution
- Preparing voice samples extracted from RMVB media archives for use in IVR (Interactive Voice Response) systems that require AMR-NB formatted audio
- Reducing file size of spoken-word RMVB content for transfer over low-bandwidth connections, since AMR-NB at 12.2 kbps produces extremely small files
- Archiving the audio portion of legacy RealMedia video content into AMR for compatibility with older Nokia or Sony Ericsson handsets that play AMR natively
Frequently Asked Questions
No — AMR-NB is specifically engineered for human speech frequencies and is a very poor choice for music or general audio content. The codec operates at only 8 kHz sample rate (narrowband), which cuts off most audio above 4 kHz, stripping out highs and much of the musical detail present in the original RMVB's AAC or MP3 audio stream. If your RMVB contains music, you will get noticeably muffled, telephone-quality output. AMR is the right choice only when the content is primarily spoken voice.
The AMR-NB specification is designed around single-channel (mono) telephony voice transmission, so it does not support stereo audio at all. When FFmpeg encodes to AMR using libopencore_amrnb, it automatically downmixes the stereo audio track from your RMVB file to mono before encoding. For speech content this is generally not a problem since voice intelligibility is preserved, but any stereo spatial separation in the original audio will be lost.
AMR-NB (Narrowband) operates at 8 kHz sample rate with bitrates from 4.75 to 12.2 kbps, while AMR-WB (Wideband) operates at 16 kHz and offers better voice quality at higher bitrates up to 23.85 kbps. This tool uses libopencore_amrnb, the narrowband codec, at its maximum bitrate of 12.2 kbps. AMR-WB (libopencore_amrwb) would produce higher-quality speech but has more restricted playback compatibility. The .amr file extension is associated with AMR-NB and is more universally recognized by mobile devices and telephony systems.
Replace the value after -b:a in the command with one of the valid AMR-NB bitrates: 4750, 5150, 5900, 6700, 7400, 7950, 10200, or 12200 (in bits per second). For example, to use the lowest bitrate for maximum compression, the command becomes: ffmpeg -i input.rmvb -vn -c:a libopencore_amrnb -b:a 4750 output.amr. Note that AMR-NB bitrates are fixed and standardized — values other than these exact numbers are not valid and FFmpeg will select the nearest supported mode.
Yes, on the command line you can use a shell loop to process multiple files. On Linux or macOS: for f in *.rmvb; do ffmpeg -i "$f" -vn -c:a libopencore_amrnb -b:a 12200 "${f%.rmvb}.amr"; done. On Windows Command Prompt: for %f in (*.rmvb) do ffmpeg -i "%f" -vn -c:a libopencore_amrnb -b:a 12200 "%~nf.amr". The browser-based tool processes one file at a time, so the local FFmpeg command is the recommended approach for batch jobs.
Generally no. The RealMedia container can carry title, author, and copyright metadata, but the AMR file format has very limited or no standardized metadata container support in most implementations. FFmpeg may not transfer RMVB metadata tags into the .amr output file, and even if written, most AMR-compatible players and telephony systems do not read or display such tags. If metadata preservation is important, consider extracting to a format like MP3 or M4A instead.
Technical Notes
RMVB (RealMedia Variable Bitrate) uses a proprietary container that FFmpeg decodes via its RealMedia demuxer, supporting the AAC and MP3 audio codecs commonly embedded in these files. The libopencore_amrnb encoder used for AMR output is an open-source implementation of the 3GPP AMR-NB standard and must be compiled into FFmpeg — most standard FFmpeg builds include it, but some minimal distributions may not. The encoder enforces strict constraints: mono channel only, 8000 Hz sample rate, and bitrates limited to the eight standardized AMR-NB codec modes. FFmpeg handles the necessary sample rate conversion and downmixing automatically. The resulting .amr file will be extremely small — at 12.2 kbps, one minute of audio produces roughly 91 KB. There is no lossless path here: audio from RMVB is fully decoded then re-encoded, meaning two generations of lossy compression are applied. The quality ceiling is effectively constrained by AMR-NB's narrowband design regardless of the original RMVB audio quality.