Convert RMVB to 3G2 — Free Online Tool
Convert RMVB files — RealNetworks' variable bitrate streaming format — to 3G2, the CDMA mobile container standard, using H.264 video and AAC audio encoded entirely in your browser. This is ideal for making older RealMedia content playable on legacy mobile devices and CDMA-based platforms without installing any software.
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FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
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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 RealVideo and RealAudio streams encoded with proprietary RealNetworks codecs, which are not natively supported in the 3G2 container. This means a full re-encode is required: the video stream is decoded from RealVideo and re-encoded to H.264 (libx264) using a CRF of 23, which targets a visually consistent quality level rather than a fixed bitrate — appropriate since RMVB itself uses variable bitrate encoding. The audio is decoded from RealAudio and re-encoded to AAC at 128k bitrate, which is the standard audio codec for 3G2 files used on CDMA mobile networks. The -movflags +faststart flag reorganizes the MP4-family container metadata to the beginning of the file, enabling progressive playback and streaming on mobile devices before the full download completes.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary, the open-source multimedia processing engine that handles all decoding, re-encoding, and container muxing for this RMVB to 3G2 conversion. |
-i input.rmvb
|
Specifies the input file in RMVB format. FFmpeg will detect the RealMedia container and demux the proprietary RealVideo and RealAudio streams for decoding. |
-c:v libx264
|
Re-encodes the decoded RealVideo stream to H.264 using the libx264 encoder, which is required because RealVideo is not a valid codec for the 3G2 container format. |
-c:a aac
|
Re-encodes the decoded RealAudio stream to AAC, the standard and most compatible audio codec for 3G2 files as specified by the 3GPP2 mobile standard. |
-crf 23
|
Sets the H.264 Constant Rate Factor to 23, targeting a consistent perceptual quality level across the output. This is appropriate for RMVB source content which was itself encoded at variable bitrate, as CRF adapts compression per-frame rather than targeting a fixed bitrate. |
-b:a 128k
|
Sets the AAC audio output bitrate to 128 kilobits per second, a standard quality level that provides good intelligibility and fidelity while keeping file size suitable for mobile storage and CDMA network transmission. |
-movflags +faststart
|
Relocates the 3G2 container's moov metadata atom to the start of the file, enabling progressive playback on mobile devices over CDMA networks before the full file has been downloaded — a key requirement for the streaming use cases 3G2 was designed for. |
output.3g2
|
Defines the output filename and instructs FFmpeg to mux the re-encoded H.264 video and AAC audio into a 3G2 container, the CDMA mobile multimedia format developed under the 3GPP2 standard. |
Common Use Cases
- Converting archived RMVB drama or anime downloads from the early 2000s into 3G2 format for playback on older CDMA feature phones or media players that lack RealPlayer support
- Preparing RealMedia variable bitrate video content for distribution over CDMA mobile networks where 3G2 is the required container format
- Transcoding RMVB lecture recordings or educational videos into 3G2 so they can be sideloaded onto legacy smartphones and viewed offline without a data connection
- Migrating a library of RMVB content from a RealPlayer-era media archive into a more portable mobile-compatible format that does not require proprietary codecs to decode
- Converting RMVB sports or news clips — commonly distributed in this format by Asian broadcasters — into 3G2 for compatibility with CDMA carrier video portals
- Generating a 3G2 version of an RMVB file to extract a standardized H.264/AAC stream for further processing in mobile video workflows
Frequently Asked Questions
The RMVB variable bitrate only describes how the original RealVideo stream was encoded; once decoded, those frames are re-encoded by libx264 using CRF 23, which is a constant quality mode that independently determines bitrate per frame based on complexity. The output 3G2 file will have its own variable bitrate determined by H.264's CRF encoding, not inherited from the RMVB source. If your source RMVB was already heavily compressed, the re-encode cannot recover lost detail, but CRF 23 will preserve the decoded quality faithfully.
RMVB uses proprietary RealVideo codecs (typically RV40 or earlier) which are incompatible with the 3G2 container, which only accepts H.264 or MJPEG video. There is no stream copy path here — the video must be fully decoded from RealVideo and re-encoded to H.264. This is computationally heavier than a remux, which is why in-browser conversion of large RMVB files may take noticeable time depending on your device.
The +faststart flag moves the moov atom (the container's index metadata) from the end of the file to the beginning. In the 3G2/MP4 family, this means a media player or mobile device can begin decoding and playing the video before the entire file has been downloaded. Without this flag, a 3G2 file would need to be fully transferred before playback could start, which is a significant problem in the low-bandwidth CDMA mobile environments 3G2 was designed for.
Increase the CRF value in the FFmpeg command — for example, change -crf 23 to -crf 28 or -crf 35. Higher CRF values allow more compression at the cost of visual quality. You can also reduce audio bitrate by changing -b:a 128k to -b:a 96k or -b:a 64k, which matters most for spoken-word content. Since 3G2 was designed for low-bitrate CDMA transmission, values like CRF 28–35 with 64k audio are common in mobile-optimized workflows.
Yes. On Linux or macOS, you can use a shell loop: for f in *.rmvb; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 128k -movflags +faststart "${f%.rmvb}.3g2"; done. On Windows Command Prompt, use: for %f in (*.rmvb) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 128k -movflags +faststart "%~nf.3g2". The in-browser tool processes one file at a time, so the FFmpeg command is the recommended approach for batch jobs.
No. Neither RMVB nor 3G2 support subtitles or chapters in the context of this conversion, and the FFmpeg command does not include any subtitle mapping flags. Any embedded RealText or SMIL-based subtitle streams in the RMVB source will be discarded during conversion. If you need subtitles, consider converting to a format like MKV or MP4 that supports external or embedded subtitle tracks.
Technical Notes
RMVB (RealMedia Variable Bitrate) was a widely used distribution format in the early-to-mid 2000s, particularly in East Asian markets for drama and anime, and relies on the proprietary RealVideo and RealAudio codec stack. Converting to 3G2 requires a full transcode of both streams since neither RealVideo nor RealAudio are valid 3G2 codec types. The output uses libx264 in CRF mode, which adapts bitrate per frame — a natural fit for content that originated in a variable bitrate format. AAC is the correct and most compatible audio codec for 3G2, aligning with the 3GPP2 specification used by CDMA carriers. Note that 3G2 does not support transparency, multiple audio tracks, subtitles, or chapter markers, so any such metadata present in the RMVB source will be silently dropped. The 3G2 container is structurally close to MP4/MOV (all are based on the ISO Base Media File Format), which is why the -movflags +faststart optimization applies here exactly as it does in MP4 conversions. Maximum audio bitrate in this tool's 3G2 profile is capped at 256k, reflecting the low-bandwidth design intent of the format. For high-motion or high-resolution RMVB source content, consider testing CRF values between 18 and 23 to avoid blocking artifacts introduced by aggressive compression on top of an already-lossy RealVideo source.