MikuVideo is a modern video tool designed for MikuMikuDance users. It solves MMD's biggest pain point: the massive uncompressed AVI files the software produces.

Key features: convert AVI/UtVideo renders to compressed MP4 using GPU acceleration (example: a 4 GB 4K AVI becomes ~40 MB as MP4), synchronize audio tracks with frame-offset adjustment, extract audio as WAV at 44,100 Hz for MMD compatibility.

The built-in player supports frame-by-frame review with up to 2000% zoom, slow-motion (4 fps) and fast playback (60 fps), and displays both MMD frame numbers and timecodes.

Built with C# and FFmpeg (LGPL), no MMD installation required.

Complete tutorial in video for beginners

What this tutorial covers

This step-by-step guide shows how to install MikuVideo, convert MMD AVI renders to MP4, and prepare background videos for MMD stage screens and motion trace — from setup to a finished MMD scene.

Installation▶ 0:00

Download MikuVideo from the MmdFr.fr menu. Windows SmartScreen may show a warning — choose Keep / Keep anyway, then open the installer and select Install for me only. If your system needs it, the installer also sets up .NET 8 automatically.

Loading and navigating videos▶ 1:04

Open a video with the Video AVI button, browse for any file type, pick from recent files, or drag and drop from File Explorer. MikuVideo has two slots — AVI video and audio WAV — each with its own play button.

Playback controls: Space toggles play/pause, the purple ball scrubs forward and backward, and the scroll wheel adjusts either playback speed or switches to frame-by-frame mode depending on which zone you're hovering.

Click once on the video screen to switch to on-screen controls: arrow keys step frame by frame, the scroll wheel zooms in/out, click-and-drag pans the image, and right-click resets zoom and pan.

Converting AVI to MP4▶ 2:02

Put the video in the first slot. Because of an MMD bug, AVI renders that don't start at frame 0 have no audio — so add the matching WAV file to the second slot and set its start offset. The Convert button merges video and audio and compresses to MP4 using your graphics card (GPU), which makes the conversion fast. Once done, the result plays automatically in the third slot.

Converting to a background video for MMD screens▶ 2:41

Rename the downloaded video to something short and recognizable, then load it into slot one and choose Convert to AVI for background/screen. This conversion runs on the CPU (slower than GPU), keeps the original resolution, and encodes at 30 fps.

Two MMD limitations to know: the AVI background format looks pixelated at high resolution, and the resulting file must stay under 1,000 MB or MMD will freeze — in 4K that's roughly under 60 seconds of footage. The same AVI also works in MikuMikuMoving (MMM) with no size limit, though MMM decodes more slowly, so a lower resolution is recommended there.

In MMD: open the Background menu and load the AVI file. On a stage, the background sits behind the walls by default — to project it onto an in-scene screen instead, disable "show background AVI file", load a 16:9 accessory, send the video to it via the background menu (mode 03), scale it (e.g. scale 5), and position it behind elements like neon lights but in front of walls. Switch the accessory from local to global, register it at frame 0, and save.

Converting a background video for motion trace▶ 5:13

Rename the file short, open it, and select the exact segment you want to trace. Convert that segment to AVI, and separately convert the matching audio track — using slot one, since only slot one supports cutting/trimming. The conversion is fast, and the result is ready to load directly into MMD.

In MMD: position the model in camera mode and register it, then position the reference video using Shift + zoom icon and the move icon. Switching back to camera mode repositions both the model and the background video together; switch to model mode to pose the bones.

Full video transcript

[0:00] Installation. Go to MmdFr.fr menu > MikuVideo and click the download button.

Choose Keep, Keep anyway, and Open. Install for me only. If your computer requires it, it will install Microsoft .NET 8.

Open the video file using the Video AVI button. Choose a video file. You can also search for all files. A list of recent files is displayed under the arrow, or drag and drop from a file explorer. There are two slots, AVI video and audio WAV. The small round button with the arrow allows you to play the slot.

[1:04] Petit tour — the space bar toggles between play and pause. The purple ball allows for fast movement; you can play forward or backward. You can adjust the playback speed using the scroll wheel in the speed zone. With the scroll wheel in the position zone, you switch to frame-by-frame mode and can move forward or backward.

Quick tour on screen — to switch to on-screen control, click once on the screen; otherwise you remain in control of the purple ball. On the screen, use the right or left arrows to switch to frame-by-frame mode. The scroll wheel on the screen zooms in and out. Click and drag to pan the video. Right-click resets zoom and pan. There are other shortcuts — see the help file.

[2:02] Convert to MP4. The video must be in the first slot. If it doesn't start at frame zero, it has no sound — this is an MMD bug. Therefore you need to add the WAV file to the second slot, and you also need to specify the start offset of the WAV file. The Convert button will merge the video and audio tracks and compress them to MP4. This is done using the graphics card, so it's relatively fast. The button then changes to "Stop convert." Once the video is converted, the third slot will play automatically.

[2:41] Convert to background video screen. You just downloaded the video — it has a long name with spaces and strange characters. To keep the reference, create a folder with that name (using Ctrl+V), then change the name to "video background." Put the source video in slot one (Video AVI) and select "Convert to AVI for background/screen."

The conversion is done by the CPU, which is much slower. It doesn't change the resolution, but it encodes at 30 frames per second. Zooming in shows the detail of a 4K video. Once the conversion is finished, the video plays with the same zoom and pan. The AVI MMD format is pixelated — feel free to use 4K with MikuMikuDance, but note that the resulting video file must be less than 1,000 megabytes, otherwise it will freeze in MMD (this is an MMD bug); in 4K that's less than 60 seconds. This format also works for MikuMikuMoving (MMM) without any size restrictions; however, decoding in MMM is slower, so you need to use a lower resolution.

With MMD, go to the Background menu and load the background AVI file. With the stage, the background is behind the walls.

To put it on the screen instead, disable "Show background AVI file." Load an accessory — the horizontal format 16 by 9 — and send the video to it via the Background menu, mode 03. Set the scale to 5, then position the screen behind the neon lights and in front of the wall. Double-click from local to global to get to the accessory. Remember to register the accessory at frame zero and save.

[5:13] Convert to background video for motion trace. The name is long, so create a folder with this name to have a trace, and rename the files with a short name. Open the video file to select the correct segment to trace, then convert this segment to AVI. Also convert the audio track — put it in slot one to cut it like the video, since only slot one allows cutting. The conversion is very fast. Everything is ready to be loaded into MMD.

Position the model in camera mode and register it. Then position the video using Shift + zoom icon and the move icon. Switching to camera mode repositions the model and the background video; to move the bones, switch back to model mode.

If you liked it, give it a thumbs up. If you want additional features or want to report a bug, you can do so on the MikuVideo page or on Discord. Have fun with MMD and MikuVideo — see you soon on MmdFr!