Convert RMVB to AMR — Free Online Tool
Convert RMVB video files to AMR audio, extracting and re-encoding the audio stream using the libopencore_amrnb codec optimized for speech. AMR's narrow-band compression makes it ideal for isolating voice content from RealMedia video recordings, shrinking files dramatically while preserving speech intelligibility.
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FFmpeg Command
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Estimated output:
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DownloadHow It Works
RMVB (RealMedia Variable Bitrate) is a container that typically holds video encoded with RealVideo and audio encoded with RealAudio or AAC. During this conversion, the video stream is completely discarded — only the audio stream is extracted and re-encoded. Because AMR (Adaptive Multi-Rate) uses its own narrow-band codec (libopencore_amrnb) that is incompatible with any audio codec found in RMVB files, a full audio transcode is required. The audio is decoded from its original format and then re-encoded at 12,200 bps using the AMR-NB codec, which was specifically engineered for speech frequencies (roughly 300 Hz–3400 Hz). The result is a compact .amr file with no video component — well-suited for voice content but not for music or wide-frequency audio.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg media processing tool. In the browser version of this tool, FFmpeg runs as a WebAssembly binary (FFmpeg.wasm) entirely within your browser — no data is sent to a server. |
-i input.rmvb
|
Specifies the input file, which is a RealMedia Variable Bitrate container. FFmpeg will detect and demux the video and audio streams contained within the RMVB file before processing. |
-c:a libopencore_amrnb
|
Sets the audio encoder to libopencore_amrnb, the open-source implementation of the AMR Narrow Band codec. This replaces whatever audio codec (RealAudio, AAC, etc.) was used in the RMVB source with AMR-NB encoding optimized for speech at 8000 Hz mono. |
-b:a 12200
|
Sets the AMR-NB encoding bitrate to 12,200 bps, which corresponds to the highest-quality AMR-NB codec mode (MR122 / Mode 7 in the 3GPP spec). This is one of eight fixed bitrate modes available in AMR-NB and provides the best speech intelligibility the format supports. |
output.amr
|
Defines the output filename with the .amr extension, which tells FFmpeg to write the result as an IETF AMR file. The output will contain only the re-encoded AMR-NB audio stream — the video from the original RMVB is not included. |
Common Use Cases
- Extracting speech or narration from old RealMedia lecture recordings or educational videos to create compact voice memos playable on feature phones and basic mobile devices
- Archiving the spoken audio track from RMVB news clips or interviews into AMR format for integration into telephony or IVR (Interactive Voice Response) systems that require AMR-NB input
- Stripping voice commentary from RMVB screen recordings or tutorial videos into a lightweight AMR file for easy playback in mobile messaging apps that natively support the AMR format
- Converting RMVB-encoded video conference recordings to AMR to reduce storage footprint when only the spoken dialogue needs to be retained
- Preparing voice-only AMR clips from RMVB sermon, podcast, or radio show recordings for distribution to users on low-bandwidth mobile networks where small file size is critical
- Testing AMR codec compatibility and speech quality by using a known RealMedia source file to evaluate how libopencore_amrnb handles different speaking styles and accents
Frequently Asked Questions
Likely not. AMR-NB (Narrow Band) is purpose-built for human speech and only faithfully reproduces frequencies between approximately 300 Hz and 3,400 Hz. Music, sound effects, and any audio with wide frequency content will sound thin, muffled, and heavily distorted after encoding with libopencore_amrnb. AMR is the right choice only when the RMVB file's audio is predominantly spoken voice.
AMR-NB operates on a fixed set of codec modes rather than arbitrary bitrates. The valid bitrates are 4750, 5150, 5900, 6700, 7400, 7950, 10200, and 12200 bps — these correspond to specific AMR speech-coding algorithm modes standardized by 3GPP. The default of 12200 bps (Mode 7, or MR122) provides the highest speech quality within the AMR-NB spec. These values are not comparable to the 128k or 320k bitrates you'd use for music formats like MP3 or AAC.
Replace the '-b:a 12200' flag with one of the other valid AMR-NB bitrate modes, such as '-b:a 7950' or '-b:a 4750'. For example: 'ffmpeg -i input.rmvb -c:a libopencore_amrnb -b:a 4750 output.amr'. Lower bitrate modes compress more aggressively and sacrifice some speech clarity, but even 4750 bps can remain intelligible for clean, close-microphone speech. Avoid going below 5900 bps if the recording has any background noise.
Yes, by swapping the codec from libopencore_amrnb to libopencore_amrwb in the FFmpeg command: 'ffmpeg -i input.rmvb -c:a libopencore_amrwb -b:a 23850 output.amr'. AMR-WB covers a wider frequency range (50 Hz–7000 Hz) and sounds noticeably better than AMR-NB, though it is less universally supported on older mobile devices. Note that valid AMR-WB bitrates are different from AMR-NB modes.
No. The AMR container format has essentially no standardized metadata support — fields like title, artist, or date that may have been embedded in the RMVB file are not carried over. The output .amr file will contain only the raw AMR audio bitstream with a minimal file header. If metadata preservation is important, you should consider an output format like M4A or MP3 instead.
Dramatically smaller. A typical RMVB file containing video might range from 150 MB to 700 MB per hour, while an AMR-NB file at 12200 bps produces roughly 5.4 MB per hour of audio. The reduction comes from two factors: all video data is discarded entirely, and the AMR audio codec compresses speech at an extremely low bitrate. For a 30-minute RMVB lecture, you might go from 300 MB down to under 3 MB.
Technical Notes
The libopencore_amrnb encoder used in this conversion is an open-source implementation of the 3GPP AMR-NB standard (3GPP TS 26.071). Because RMVB files can contain audio encoded as RealAudio, AAC, or occasionally MP3, FFmpeg must first fully decode whichever audio codec is present before passing PCM samples to the AMR encoder — there is no possibility of stream copying. The AMR-NB codec internally resamples audio to 8000 Hz mono regardless of the RMVB source's sample rate or channel count, so stereo or high-sample-rate audio sources are automatically downmixed and downsampled. This is a lossy-to-lossy conversion chain, meaning audio quality degrades at both the decode (RMVB) and encode (AMR) stages. The output .amr file uses the IETF AMR storage format with the '#!AMR
' magic header, which is broadly compatible with Android, older Nokia and feature phones, and telephony middleware. Chapters, subtitles, and secondary audio tracks present in some RMVB files are not supported by AMR and are silently dropped. If you are processing a file longer than 1 GB, the displayed FFmpeg command can be run locally on your desktop without any file size restriction.
' magic header, which is broadly compatible with Android, older Nokia and feature phones, and telephony middleware. Chapters, subtitles, and secondary audio tracks present in some RMVB files are not supported by AMR and are silently dropped. If you are processing a file longer than 1 GB, the displayed FFmpeg command can be run locally on your desktop without any file size restriction.