Convert RMVB to ALAC — Free Online Tool
Convert RMVB video files to ALAC (Apple Lossless Audio Codec) M4A audio, extracting and losslessly compressing the audio track from RealNetworks' variable-bitrate container into an Apple-native format. This is ideal for archiving the audio from RMVB content with zero quality degradation, since ALAC stores audio bit-for-bit accurately in an iTunes-compatible M4A container.
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FFmpeg Command
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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 files typically contain video encoded with RealVideo and audio encoded with RealAudio or AAC. During this conversion, FFmpeg demuxes the RMVB container and extracts the audio stream. Because ALAC is a lossless codec and the source audio in RMVB is lossy, the audio is decoded to raw PCM first and then re-encoded using Apple's lossless ALAC codec — meaning no additional lossy generation loss is introduced beyond what already existed in the source. The video stream is discarded entirely, and the resulting audio is wrapped in an MPEG-4 (.m4a) container, which is natively supported by Apple devices, iTunes, and the broader Apple ecosystem.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, the underlying engine that handles all demuxing, decoding, encoding, and muxing for this RMVB-to-ALAC conversion. |
-i input.rmvb
|
Specifies the input file — an RMVB container, RealNetworks' variable-bitrate variant of the RealMedia format. FFmpeg uses its RMVB demuxer to read the file and identify the contained audio and video streams. |
-c:a alac
|
Sets the audio codec to ALAC (Apple Lossless Audio Codec), instructing FFmpeg to decode the source audio from the RMVB and re-encode it losslessly into Apple's ALAC format for storage in the M4A container. |
-c:a alac
|
This flag appears twice in the resolved command (a redundant but harmless duplication). Both instances confirm the use of the ALAC encoder for the audio stream — the second occurrence has no additional effect and FFmpeg simply applies the last valid value for each stream option. |
output.m4a
|
Defines the output file as an M4A file, which is an MPEG-4 audio container. FFmpeg infers from the .m4a extension that the output should be wrapped in an MPEG-4 container, the correct and native home for ALAC audio and the format recognized by iTunes, Apple Music, and iOS devices. |
Common Use Cases
- Extracting a music concert or live performance recorded in RMVB format to preserve the audio as a lossless ALAC archive for an Apple Music library
- Pulling dialogue or narration audio from old RMVB educational or lecture videos into a losslessly-stored M4A file for long-term archiving
- Converting a Chinese drama or film distributed in RMVB format to ALAC so the audio can be synced to a replacement video track without re-encoding losses stacking up
- Archiving the audio from legacy RealMedia video content before the original RMVB files are retired or deleted, ensuring no further quality degradation over time
- Preparing RMVB-sourced audio for import into GarageBand, Logic Pro, or Final Cut Pro, which natively support ALAC M4A files
- Stripping the audio from an RMVB movie to create a clean ALAC reference track for subtitle-syncing or audio-description dubbing workflows
Frequently Asked Questions
No — and this is an important distinction. RMVB stores audio in a lossy format (commonly RealAudio or AAC), so some audio information was permanently discarded when the original RMVB was created. Converting to ALAC does not recover that lost data. What ALAC guarantees is that the decoded audio from the RMVB is preserved exactly, with no further quality degradation introduced by the conversion itself. You end up with a lossless copy of what was in the RMVB, not a lossless copy of the original recording.
RMVB uses lossy compression aggressively for both video and audio to minimize file size. When this tool extracts just the audio and re-encodes it as ALAC, the lossless compression is mathematically much less aggressive than lossy codecs — it can only remove redundancy it can perfectly reconstruct, not discard audio data. Additionally, the RMVB file's size included both video and audio streams, so comparing file sizes directly is misleading; the ALAC file contains only audio, but stored with lossless fidelity.
RMVB containers have limited and non-standardized metadata support, so most RMVB files carry little to no embedded metadata. The ALAC M4A container (MPEG-4) has robust support for iTunes-style metadata tags, but FFmpeg can only transfer metadata that exists in the source. You will likely need to manually tag the resulting M4A file using a tool like MusicBrainz Picard, iTunes, or Mp3tag after conversion.
Yes, ALAC has been open-sourced by Apple and is supported well beyond the Apple ecosystem. VLC, foobar2000, and most modern Android devices can play ALAC M4A files natively. However, some older or budget media players may not support ALAC, in which case converting to FLAC would be a more universally compatible lossless alternative.
The single-file command shown is 'ffmpeg -i input.rmvb -c:a alac -c:a alac output.m4a'. To batch process on Linux or macOS, you can run: 'for f in *.rmvb; do ffmpeg -i "$f" -c:a alac "${f%.rmvb}.m4a"; done'. On Windows Command Prompt, use: 'for %f in (*.rmvb) do ffmpeg -i "%f" -c:a alac "%~nf.m4a"'. This loops through every RMVB file in the current directory and produces a corresponding M4A file.
ALAC is a lossless codec, meaning it has no quality parameter — it always reproduces the audio exactly as decoded from the source. There is no bitrate setting to tune because the file size is determined by the audio content itself and the efficiency of the lossless compression algorithm, not by a quality slider. This is fundamentally different from lossy formats like MP3 or AAC where you trade file size against audio fidelity.
Technical Notes
RMVB (RealMedia Variable Bitrate) is a legacy container developed by RealNetworks that saw heavy distribution use in the late 1990s and 2000s, particularly for Asian film and drama content. Its audio tracks are most commonly encoded with RealAudio or, in later files, AAC. FFmpeg's RMVB demuxer is mature and handles most RMVB files reliably, though very old or malformed RMVB files may cause seeking or decoding issues. The ALAC encoder in FFmpeg uses Apple's reference implementation and produces fully compliant M4A files. One known limitation: because RMVB does not support subtitle tracks or multiple audio streams in any standardized way, this conversion only handles the primary audio track — no subtitle or secondary track migration is possible. The output M4A container does support iTunes chapter markers, but since RMVB has no chapter data, none will be present in the output. If the source RMVB audio is RealAudio (not AAC), it must be fully decoded before ALAC encoding, which is the expected behavior here. Users dealing with RMVB files larger than 1GB should use the displayed FFmpeg command locally, as the browser-based tool supports files up to 1GB.