MJPEG to RMVB Converter

MJPEG to RMVB — What the Output Really Is

Motion JPEG is video stored the crudest possible way: every frame is a complete JPEG, nothing is shared between frames, and a one-minute recording routinely runs to hundreds of megabytes. RMVB is RealNetworks' "RealMedia Variable Bitrate" — the name attached to the RealMedia files that circulated widely for anime fansubs and downloaded TV in the early 2000s.

Before you convert, it is worth being precise about what this page produces, because "RMVB" is a looser label than it looks:

• The container written is RealMedia. We compared the same encode saved as .rm and as .rmvb and the files were byte-identical, both beginning with the .RMF signature. RMVB is a naming convention on top of RealMedia, not a separate format.
• The video inside is RealVideo 1.0 or 2.0 — those are the only two RealVideo generations that can be encoded. RealVideo 3.0, 4.0 and 6.0, which is what most RMVB files from the format's heyday actually contain, can be decoded but not written.

So this is a genuine RealMedia file under the .rmvb name. It is not a reconstruction of a 2004-era RMVB rip, and nothing here can make it one.

How to Convert MJPEG to RMVB

1. Upload Your MJPEG File: Drag the file in or click "+ Add Files". IP-camera exports, webcam captures, microscope acquisitions and old camcorder clips all work, and several can be queued together.
2. Choose RealVideo 1.0 or 2.0: RealVideo 1.0 is preselected; RealVideo 2.0 is a little more efficient at the same setting — on an 848 × 480 test clip it produced about 5% smaller output. Audio Codec offers AAC, AC3 and RealAudio 1.0, and is worth setting deliberately rather than left alone.
3. Set File Compression and Video Resolution: File Compression opens on Quality Preset. Constant Quality exposes a 1-to-31 quantiser slider opening at 5, where lower means better quality — do not drag it below 3, for the reason in the next section. Specific file size, Constant Bitrate and Constraint Quality are the other modes. Video resolution is preselected to Keep original.
4. Convert and Download: Click "Convert" and save the .rmvb. If you use Trim, leave the start time at 0 — see the errors section. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark.

Walk-through: the Quality Slider and RealMedia's 64 KB Wall

RealMedia cannot carry a packet larger than 64 kilobytes, and at the best quality settings RealVideo produces frames bigger than that. The bitrate-based modes are protected — the pipeline caps a requested bitrate at roughly 4.4 Mbit/s at 25 frames per second, derived directly from the packet limit — but the Constant Quality path never sets a bitrate, so nothing there is capped.

We swept the slider against a four-second 848 × 480 clip (source: 3,160,672 bytes of Motion JPEG):

Where the wall sits depends on frame size and how busy the picture is — the same clip scaled to 320 × 240 encoded happily at 1. The reliable rule: 5 is safe, and if a job fails, raise the number or lower the resolution.

One related thing worth knowing: Constraint Quality shows a Max bitrate box, but RealVideo encoders do not accept the rate-control parameters it produces, so they are discarded before encoding. If you want a real ceiling, use Constant Bitrate.

What Changes Between the Two Formats

Common Errors and How to Fix Them

• "The output is empty or a few hundred bytes." You set a Trim start time above zero. A raw Motion JPEG stream carries no timestamps, so seeking into it returns nothing — we measured a trim starting at 2 seconds producing a container with zero frames, while starting at 0 with a 2-second duration produced exactly 2.000 seconds. Even a 0.04-second offset — one frame at 25 fps — comes back empty. Leave the start at 0 and set only the duration.
• "The conversion failed and I had turned the quality up." That is the 64 KB packet wall described above. Move Constant Quality back to 5 or higher.
• "My 854-pixel-wide video came back 848 wide." RealVideo requires both dimensions to be multiples of 16, and each axis is rounded down to the nearest one. This is not cosmetic: we encoded an 854-wide frame directly to RealVideo and the encoder refused to open at all, writing a zero-byte file. The 0.7% change in shape is invisible; the alternative is no file.
• "The clip is silent." A raw Motion JPEG stream has no audio track — the format provides nowhere for one — so there is nothing to carry across. Sources that are really AVI or MOV under an .mjpeg name do carry audio and will use the Audio Codec setting.
• "The playback speed is wrong." A raw Motion JPEG stream stores no frame rate either, so a nominal 25 fps is assumed when reading it. Footage shot at 15 or 30 will run fast or slow. Converting from the original container instead solves this.

When This Doesn't Work

If your file is really an AVI, MOV or MKV that someone renamed to .mjpeg, it will convert — files are demuxed by their actual contents — but the result is better from the page matching the real extension, because those containers record frame rate and carry audio that a raw stream cannot.

And if nobody specifically asked for RealMedia, do not use it. Player support has been shrinking for two decades, the two encodable RealVideo generations are far behind anything modern on quality per byte, and the 64 KB packet limit puts a hard ceiling on how good the picture can get. MJPEG to MP4 produces a far better file that everything opens. Choose RMVB when an archive, a catalogue or a piece of legacy software requires the extension.

Frequently Asked Questions

Is .rmvb different from .rm here?

Not in the bytes. We wrote the same encode under both names and the files compared byte-for-byte equal, both starting with the .RMF RealMedia signature. If a system wants one specific extension, pick that one; otherwise MJPEG to RM gives you exactly the same result under the more literal name.

Why can't I choose RealVideo 9 or 10?

Because they cannot be encoded — only decoded. The tooling can read RealVideo 3.0, 4.0 and 6.0 streams but can only write RealVideo 1.0 and 2.0, which is why the dropdown has two entries. This is a real constraint on what an RMVB produced today can contain, and it is worth knowing if you are trying to match an existing collection.

Does the name RMVB mean the output is variable bitrate?

Not by itself. The extension is a convention, and what you actually get depends on the File Compression mode you choose here: Constant Quality and Quality Preset vary the rate with the content, Constant Bitrate does not. Selecting .rmvb does not switch anything into a variable-rate mode on its own.

Which audio codec should I pick if my source has sound?

AAC or AC3 — both preserve the source's sample rate and channel count. Avoid RealAudio 1.0 unless something demands it: we measured it producing a fixed 8 kHz mono stream at 8 kbit/s, which is a 1995 speech codec doing exactly what it was designed for and nothing more. On music or ambient sound the result is unusable.

RealVideo 1.0 or 2.0 — does it matter?

Slightly. RV20 is the later of the two and encodes a little more efficiently: 1,363,483 bytes against RV10's 1,437,877 on the same clip and setting, roughly 5%. RV10 is preselected because it is the more broadly decodable. If a target system names a version, match it; otherwise the difference is small enough to ignore.

How much smaller will the RMVB be than the MJPEG?

Quite a lot, because almost anything beats storing every frame as a full JPEG. Our four-second 848 × 480 sample went from 3,160,672 bytes to 1,437,877 at the default quality setting, and to 216,684 at the far end of the slider. The trade-off is picture quality: RealVideo at quality 31 looks like 2002.

Can I keep the original resolution?

Yes — Keep original is preselected — subject to the multiple-of-16 rounding, which will shave up to fifteen pixels off each axis. For 640 × 480, 1280 × 720 and 1920 × 1080 sources nothing changes at all, since all six numbers already divide by 16.

Why is there no deinterlacing option?

Because there is no deinterlacing anywhere in the conversion path. This rarely matters for Motion JPEG, which is nearly always progressive, but it is worth knowing if your source came from an interlaced capture card — the comb artefacts will be re-encoded into the output as part of the picture.

Can I convert a batch in one pass?

Yes. Queue the files and they are processed with the same codec, quality and resolution settings. Since the frame-size rounding is applied per file, clips of different dimensions each get their own nearest multiple of 16 rather than being forced to a common size.