Convert RMVB to FLAC — Free Online Tool
Extract and convert the audio track from an RMVB video file into a high-quality FLAC archive. Because RMVB uses lossy compression internally, this tool decodes the RealMedia audio stream and re-encodes it to lossless FLAC — ideal for preserving the best possible quality from your source material.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your RMVB file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
RMVB (RealMedia Variable Bitrate) is a proprietary container that stores video and audio in lossy-compressed streams, typically encoded with RealAudio or AAC. Converting to FLAC is an audio-extraction process: FFmpeg discards the video track entirely, decodes the compressed audio stream from the RMVB container, and re-encodes the raw PCM audio data into the FLAC lossless format. Because the original RMVB audio was already lossy-compressed, the resulting FLAC file preserves every bit of audio information that survived that original encoding — it won't recover detail lost during RMVB compression, but it guarantees no further quality degradation occurs during or after this conversion. The output is a standalone FLAC file with no video.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary, the open-source multimedia processing engine that handles decoding the proprietary RMVB container and encoding the FLAC output entirely within your browser via WebAssembly. |
-i input.rmvb
|
Specifies the input RMVB file. FFmpeg reads the RealMedia Variable Bitrate container, identifies the contained video and audio streams, and makes them available for processing. |
-c:a flac
|
Sets the audio codec to FLAC (Free Lossless Audio Codec). FFmpeg decodes the lossy audio stream from the RMVB file to raw PCM and then re-encodes it into lossless FLAC format — the only codec supported by the FLAC container. |
-compression_level 5
|
Sets the FLAC encoder's compression effort to 5 on a 0–8 scale. This is the default balanced setting — it affects only how aggressively the lossless compression algorithm packs the data, never the audio quality or fidelity of the output. |
output.flac
|
Defines the output filename with a .flac extension. Because FLAC is a pure audio container, FFmpeg automatically drops the video track from the RMVB source — no explicit video-discard flag is needed when the output format has no video capability. |
Common Use Cases
- Archiving the audio from classic anime or foreign films distributed in RMVB format, preserving the best available quality in a future-proof open format
- Extracting a music soundtrack or score from an RMVB video file to add to a lossless audio library managed by software like foobar2000 or Plex
- Preparing RMVB-sourced audio for audio editing or mastering in a DAW, where a lossless intermediate format avoids generational quality loss from repeated lossy encode/decode cycles
- Converting RMVB lecture recordings or spoken-word content to FLAC for long-term archival storage where file integrity and no further degradation is more important than file size
- Stripping audio from RMVB video files downloaded from older Chinese video platforms (where RMVB was historically dominant) to create a portable, device-agnostic audio collection
Frequently Asked Questions
No — FLAC is lossless, but it cannot restore audio detail that was already discarded by RMVB's lossy compression. What this conversion guarantees is that no additional quality loss occurs: the decoded PCM audio from the RMVB stream is captured exactly and stored without further compression artifacts. Your FLAC file will sound identical to the audio in the source RMVB, but not better than it.
RMVB stores audio using lossy compression, which achieves small file sizes by permanently discarding audio data the encoder deems inaudible. FLAC stores the full decoded audio waveform using lossless compression, so it retains all remaining audio data. A typical 700MB RMVB movie might produce a FLAC audio file of 200–400MB depending on the duration and original audio bitrate — a significant size increase for the audio alone, which is expected when moving from lossy to lossless storage.
Older RMVB files commonly contain RealAudio (Cook or ATRAC variants), while newer ones may use AAC. FFmpeg decodes whichever audio codec is present in the RMVB container before re-encoding to FLAC, so the output quality is bounded by whatever the original codec preserved. If FFmpeg cannot decode a particularly obscure or old RealAudio variant, the conversion may fail — this is a known limitation of legacy RealMedia codec support.
The `-compression_level` flag controls how hard the FLAC encoder works to compress the audio data, on a scale from 0 (fastest, largest file) to 8 (slowest, smallest file). The default used here is 5, which is a balanced choice. Importantly, this setting affects only encode speed and file size — it has absolutely no effect on audio quality, since FLAC is always lossless regardless of compression level. To use maximum compression, change the command to: ffmpeg -i input.rmvb -c:a flac -compression_level 8 output.flac
RMVB files rarely carry rich metadata tags, and any that do exist may not map cleanly to FLAC's Vorbis comment metadata standard during conversion. FFmpeg will attempt to copy compatible metadata fields, but you should expect to manually verify and re-tag the FLAC file afterward using a tool like Mp3tag or beets. FLAC has excellent metadata support once the file is created.
Yes. On Linux or macOS you can use a shell loop: `for f in *.rmvb; do ffmpeg -i "$f" -c:a flac -compression_level 5 "${f%.rmvb}.flac"; done`. On Windows Command Prompt, use: `for %f in (*.rmvb) do ffmpeg -i "%f" -c:a flac -compression_level 5 "%~nf.flac"`. This browser-based tool processes one file at a time, but the displayed FFmpeg command is provided precisely so you can run bulk operations locally.
Technical Notes
RMVB's variable bitrate design means the audio stream's effective quality can vary significantly across files — a low-bitrate RMVB encode will produce a FLAC that is losslessly accurate to a poor source. FFmpeg's support for legacy RealAudio codecs (particularly Cook/RealAudio G2 and older variants) has historically been inconsistent; if your RMVB file was encoded many years ago with a proprietary RealAudio codec, decoding may be incomplete or the conversion may error out. Modern RMVB files using AAC audio convert reliably. The video stream is completely dropped during this conversion since FLAC is a pure audio container with no video support. FLAC's `-compression_level` parameter is a CPU/size tradeoff only and never affects decoded audio fidelity. The output FLAC file will be sampled at whatever rate the original RMVB audio used — typically 44100 Hz or 48000 Hz — and no sample rate conversion is applied unless explicitly added to the command.