RM to MJPEG Converter

RM to MJPEG: Turning a RealMedia Clip Into a Stack of JPEGs

Motion JPEG is not really a video codec in the modern sense. It has no motion compensation, no prediction, and no relationship between one frame and the next — each frame is simply a complete JPEG image, and a .mjpeg file is those images written one after another with no container around them. That property is exactly why editors, machine-vision pipelines and frame-accurate review tools still ask for it, and it is also why the file is enormous. This page decodes the RealVideo inside your .rm and re-encodes every frame as a JPEG.

Because there is no container, there is nowhere for a soundtrack to live. That is the single most important thing to know before you convert, and the page's own Audio Codec dropdown does not make it obvious — see below.

How to Convert RM to MJPEG

1. Upload Your RM File: Drag the .rm onto the page or click "+ Add Files". Several clips can be queued and share one set of settings; this page accepts the .rm extension.
2. Leave Video Codec on MJPEG: Video Codec lists MJPEG and nothing else, which is correct — the .mjpeg extension names the codec, so there is no alternative to pick.
3. Set File Compression, Video resolution and Trim: With MJPEG resolved, File Compression offers exactly two modes: Quality Preset, which opens on "Very High (Recommended)", and Constant Quality, whose slider is a 2–31 quantiser scale opening at 5, where lower is better. Specific file size, Constant Bitrate, Variable Bitrate and Constraint Quality do not render on this target. Video resolution opens on "Keep original" and Trim on "Unchanged" — both are worth using here for reasons of size.
4. Convert and Download: Click Convert and save the .mjpeg. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark.

The Audio Dropdown Is Real, the Audio Output Is Not

Audio Codec on this page renders a full list — AAC, AC3, DTS (DCA), EAC3, FLAC, MP2, MP3, six PCM variants, Speex, Vorbis, WMA v1 and WMA v2 — with MP3 preselected. None of it reaches the output. A raw MJPEG stream is a concatenation of JPEG images and has no stream table, no interleaving and no place to store sound.

We measured it: converting a test .rm with an MP3 audio codec explicitly requested produced a file the muxer reported as video: 4057KiB, audio: 0KiB, and reading the result back showed a single MJPEG video stream and no audio stream. The RealAudio track is dropped. Treat the Audio Codec group on this page as inert.

If you need the sound, you need a container. RM to AVI will carry Motion JPEG video and an audio track in the same file, which is what most people asking for "MJPEG" actually want — AVI was the classic MJPEG wrapper. RM to MP4 is the choice if you want something small and playable rather than frame-independent.

What the Output Looks Like, and How Big It Gets

We converted a ten-second 640 × 480 test clip and inspected the result:

That five-fold growth is not a settings mistake, it is the format. RealVideo spends most of its bits on the first frame of a scene and stores subsequent frames as differences; MJPEG re-encodes the entire picture 25 or 30 times a second. Expect the same order of increase on your own files, and expect it to scale with resolution and duration rather than with the source file size.

Three things actually reduce it: raise the Constant Quality number towards 31 (coarser JPEG), reduce the frame size under Video resolution, or cut the clip down with Trim → Time Range. Trimming first is usually the highest-leverage move, because MJPEG's cost is strictly proportional to how many frames you ask for.

RM as a Source

Most .rm files date from an era when bandwidth was the binding constraint, so the source picture is usually small and heavily compressed. Converting to MJPEG cannot improve it — the JPEG pass reproduces the artefacts already present, at considerable expense in bytes. Keep the Quality Preset high enough that you are not adding a second visible generation of damage, but do not expect a high number to do anything for the source's own limitations.

Frequently Asked Questions

Why is there no audio in my .mjpeg file?

Because the format cannot hold any. A .mjpeg file is a sequence of complete JPEG images with no container wrapped around them, so there is no stream table and no interleaving — nothing to put a soundtrack in. The Audio Codec dropdown on this page renders a full list with MP3 preselected, but none of those settings affect the output. We measured a conversion with MP3 explicitly requested: the muxer reported audio: 0KiB and the result contained a video stream only. Use RM to AVI if you want Motion JPEG video with sound.

Why is the output five times larger than the RM I uploaded?

Because MJPEG has no interframe compression. Every frame is stored as a complete, independent JPEG, so a static shot costs exactly as much as a fast pan. RealVideo, like every modern codec, stores most frames as differences from their neighbours and is therefore dramatically more efficient. Our ten-second test grew from 821,853 bytes to 4,153,870 bytes. Cutting the duration with Trim, lowering the frame size, or raising the Constant Quality value towards 31 are the ways to bring that down.

What is the 2–31 slider under Constant Quality?

It is the JPEG quantiser scale that the MJPEG encoder uses, not a constant-rate-factor scale. It opens at 5. Lower means finer quantisation and better quality, so 2 is the best the encoder offers and 31 the coarsest. Because every frame is quantised independently, moving this slider changes the size of every frame proportionally — it is the most direct size control on this page, and unlike Quality Preset it has an exact meaning.

Why can't I set a target file size or a bitrate here?

Because those modes do not render on an MJPEG target. With the codec resolved to MJPEG, the File Compression group offers Quality Preset and Constant Quality only; Specific file size, Constant Bitrate, Variable Bitrate and Constraint Quality are all hidden. That reflects how the codec works — MJPEG has no rate-control loop looking across frames, so a bitrate target has nothing to steer. Control the size through quality, resolution and duration instead.

What actually opens a .mjpeg file?

VLC, mpv and other FFmpeg-based players read it. Video editors and machine-vision tools that ask for Motion JPEG generally accept it, and many will also happily take it as a sequence of stills. What will not open it: browsers, phone galleries, and most operating-system default players, because there is no container to describe what the file is. If you need something a person can double-click, convert to MP4 instead.

Is MJPEG the same as an animated GIF or a folder of JPEGs?

Conceptually it is very close to a folder of JPEGs — the frames really are complete, independent JPEG images concatenated into one file. The differences are that a .mjpeg has no per-frame filenames or timing information stored in the stream, and that it carries full 24-bit colour, where a GIF is limited to a 256-colour palette per frame. If you want individual image files rather than one stream, a frame-extraction conversion to JPG gives you that.

Will converting to MJPEG make an old RealMedia clip look sharper?

No. The .rm was encoded at streaming-era bitrates, and everything RealVideo discarded is gone before this conversion begins. What MJPEG adds is frame independence — every frame becomes a keyframe, which is genuinely useful for scrubbing and frame-accurate editing — but not detail. Keep the quality high so the JPEG pass does not compound the existing artefacts, and set expectations from the source rather than the target.

Does this remove interlacing from an old broadcast-sourced RM?

No. There is no deinterlacing step anywhere in this pipeline, so if the source frames contain combing — the horizontal teeth along moving edges that come from interlaced capture — every JPEG in the output will contain it too. Because MJPEG stores each frame in full, the comb is if anything more visible than in the original. Deinterlace in a video editor before converting if the footage has significant motion.

What happens to the file I upload?

It is uploaded over an encrypted connection, decoded and re-encoded on our servers, and both the upload and the resulting .mjpeg are deleted automatically after a few hours. Nothing is shared or made public, no watermark is added, and no account is required. Bear in mind that MJPEG output is large, so allow time for the download as well as the upload.