Trim MJPEG

How to Trim MJPEG Files Online

1. Upload Your MJPEG File: Drag and drop the clip onto the page or click "+ Add Files" to browse. Files stay in your browser session — no account, no upload to a third-party host.
2. Set the Time Range: Under "Trim," pick "Time Range" and enter a start time and duration in HH:MM:SS.ms. Because every MJPEG frame is a complete JPEG, cuts are frame-accurate without re-encoding ripple.
3. Adjust Compression and Resolution (Optional): Under "File Compression," choose Quality Preset (Highest to Lowest), Target file size (%), Specific file size, Constant Bitrate, Variable Bitrate, Constant Quality (CRF), or Constraint Quality. Under "Video resolution," keep original, pick a preset (4K, 1440p, 1080p, 720p, 480p), set width/height, or scale by percentage.
4. Trim and Download: Click "Trim." The output file downloads when processing finishes. Re-run with new times to extract additional segments.

Why Trim MJPEG Footage?

Motion JPEG stores every frame as an independent JPEG with no inter-frame prediction, so it remains the working format for IP security cameras, USB webcams, machine-vision rigs, scientific microscopes, and older flash-card camcorders. Recordings tend to be long, repetitive, and large — a 1080p MJPEG stream can run 5-20x the size of equivalent H.264 footage at the same resolution, per IPVM and surveillance-industry comparisons. Trimming is how you isolate the part that matters before review, sharing, or archival.

• Surveillance incident clips — extract a 30-second window around a doorbell trigger or motion event from an hours-long IP-camera recording, keeping it in MJPEG so your DVR/NVR review software still opens it.
• Lab and microscopy captures — pull the seconds where a reaction, cell division, or particle event occurs out of a continuous capture without re-encoding artifacts that obscure measurement frames.
• Webcam and screen recording cleanup — drop the first few seconds of fumbling and any tail of dead air from a Logitech, Razer, or generic UVC capture saved as MJPEG-in-AVI.
• Industrial machine-vision review — isolate the inspection pass that flagged a defect from a high-frame-rate line capture, preserving each frame's full quality for visual QA.
• Legacy camcorder footage — older Nikon, Canon, and Casio still cameras saved video as MJPEG-in-AVI or MJPEG-in-MOV; trim before transcoding to H.264 for easier sharing.
• Frame-accurate edit prep — because MJPEG is intra-only, each cut lands exactly on the chosen frame, useful when you'll later export individual frames as JPEG stills.

MJPEG vs H.264 — Why MJPEG Files Are So Large

Property	MJPEG	H.264 (AVC)
Compression type	Intra-frame only (every frame self-contained)	Intra + inter-frame (I, P, B frames)
Typical compression ratio	~1:20	~1:50 or better
1080p IP-camera bitrate	~25-50 Mbit/s	~2-8 Mbit/s
Frame-accurate cut without re-encoding	Yes (every frame is a key frame)	Only at I-frames; otherwise requires re-encode
Decoder complexity	Low (any JPEG decoder)	Higher (motion-vector reconstruction)
Latency in live streams	Very low	Low to moderate (GOP-dependent)
Common containers	AVI, MOV, MKV, raw .mjpeg, RTP	MP4, MKV, MOV, TS

Trim Output Quality Modes

Mode	What it does	When to use it
Stream copy (no re-encode)	Keeps original JPEG frames as-is	Default for surveillance/evidence — preserves exact pixels
Quality Preset (Highest to Lowest)	Re-encodes JPEG frames at preset quality	Quick size reduction with predictable visual quality
Target file size (%)	Scales output to a percentage of input size	Hitting a quota for upload or storage
Constant Quality (CRF)	Fixed per-frame quality target	Mixed-content footage where some scenes are busier than others
Constant Bitrate	Locks the bitrate ceiling	Streaming pipelines that need predictable bandwidth

Frequently Asked Questions

Will trimming an MJPEG file lose any image quality?

If you keep the same MJPEG output and don't change compression or resolution, the trim is a stream copy — the surviving JPEG frames are byte-identical to the source. Quality only changes when you switch on a compression mode (Quality Preset, CRF, target size) or change the resolution, which forces a re-encode.

Why is my MJPEG so much larger than equivalent MP4 video?

MJPEG has no inter-frame compression — each frame is a full JPEG with no reference to its neighbors. H.264 and H.265 reuse pixels across frames and only encode the differences, which Wikipedia notes lets them reach roughly 1:50 compression versus MJPEG's ~1:20. For static surveillance scenes the gap widens further because most pixels barely change. If size matters more than per-frame independence, convert MJPEG to MP4 after trimming.

Can I cut on any frame, or only at keyframes like with H.264?

Any frame. Because MJPEG has no P-frames or B-frames, every frame is effectively a keyframe. That's why intra-only formats like MJPEG, ProRes, and DNxHD are favored for editing timelines — slice points fall exactly where you specify, no GOP boundary rounding.

My security camera saves footage as .avi or .mov — is that still MJPEG?

Often yes. MJPEG is a codec, not a container. IP cameras and DVRs commonly wrap MJPEG inside AVI or MOV files; some store raw .mjpeg streams. The trimmer accepts the .mjpeg extension; if your camera writes .avi or .mov but uses MJPEG inside, use the matching tool (Trim AVI or Trim MOV) — the same trim controls apply.

Can I extract individual frames as JPEG stills after trimming?

Yes — that's where MJPEG shines for evidence and lab work. After trimming to the segment you want, run Convert MJPEG to JPG to export every frame as a separate JPEG file. Because each frame was already a JPEG inside the MJPEG stream, the export is essentially repackaging, not re-encoding.

How long can the source MJPEG file be?

The trimmer processes hours-long captures, but very large uploads (multi-GB surveillance footage) take longer to upload and process. If your file is over a couple of GB, consider trimming on the camera/DVR first to a rough window, then using this tool to refine the cut and apply compression.

Will trimming preserve the timestamp overlay burned into my surveillance footage?

Yes. Surveillance timestamp overlays are baked into each frame's pixel data — they're part of the JPEG itself, not a separate metadata track. Trimming and even re-encoding will keep them visible. What you may lose is the container-level timestamp metadata some DVRs add; that's separate from the visible burn-in.

Should I trim as MJPEG or convert to a smaller format first?

If the footage will stay in a system that requires MJPEG (some legacy NVRs, scientific capture software, evidence chains that mandate the original codec), trim as MJPEG. If you're trimming to share, archive, or upload, save bandwidth by trimming first, then convert MJPEG to MP4 or convert MJPEG to MKV — going through trim-then-convert keeps the working file small at every step.

Does trimming work for MJPEG inside Matroska (.mkv) or QuickTime (.mov)?

This page is tuned for the .mjpeg extension. For MJPEG wrapped in other containers, the matching trimmer (Trim MKV, Trim MOV, Trim AVI) handles the same codec without you having to remux first.