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Dramatically Decrease AVI File size before uploading YouTube videos

A Feature Article by Reggie Dentmore on LearnMMD.comHow can I decrease AVI file size when I Render to AVI in MMD? How can I make my MMD .avi file size smaller? Where can i get Prism video converting software?

Dramatically Decrease AVI File size
before uploading YouTube videos


Before I start this article…

Experienced MMD animators have let me know…
Do NOT reduce that AVI file size using the method I describe in this article. The original, large AVI file MMD produces yields the best quality of video you can upload to YouTube. Our Trackdancer2015 explains this in his article:
DO NOT reduce AVI file sizes that go up to YouTube.

For MY use of MMD, for the resolutions I use, I find the quality loss to be negligible and, with my slow internet connection, the upload speed I gain, with a smaller AVI file to upload, is a “plus!”

I have been using the “UtVideo YUV420 BT.709 VCM” codec for my video compression tool when doing a Render to AVI in MikuMikuDance. The resulting video is excellent… and the final AVI file-size is pretty large! … but TRY this Codec… you will like it.

Download Ut Video Codec Suite 17

Download the install.exe, install it… and when you are running MMD, see the UTVideo option as a compressor choice as you render to AVI. … You will see several UTVideo codecs in the list, I always use the topmost choice, the .709 version.

I just made a twenty-two second animation with the resulting video being almost 80 megabytes!

For several months, now, I have been using Prism® video conversion software to reprocess my MMD AVI’s into much smaller final file-sizes. After running THIS 80Mb video file through Prism, my final file size is not-quite THREE megabytes…


and, with the settings I have used, I can see and hear no difference in the quality of that final video. …

… Okay, THIS exact video has no soundtrack… no sound. … but look at that image… My original ARROW video (the one named Weds PM.avi) was over 400Mb, and with the soundtrack and the beautiful video images, it was reduced to only 20Mb.

Download Prism®


Download and install Prism. It’s easy and it’s free.  Each time you USE Prism, a little pop-up asks if you are using it for personal use (no charge) or for commercial purposes (need to pay for the use). For our hobby of MMD, just check “personal use”.

Setup Prism


On the Prism GUI, set the output to AVI. … and then setup your Encoder options.


For my latest little Hologram video, I just went with the defaults (as shown in that image). For my Arrow animation, my original video was so huge, that I set the encoder for some of what I thought would yield a minimum file size, maximum compression. … and I chose the “UtVideo YUV420 BT.709 VCM” option rather than the default  “H264 (native)”… output Mp3 audio at only “22050 Hz, 128 kbps, stereo” as I tried to get that smaller file size.

As I said, “Arrow” went from nearly 800Mb (my actual final, finished AVI size) to only about 20Mb… and I feel the final video has all of the quality that it needed after it got through the YouTube processing-mill.

Enjoy Prism…

So… download Prism video converting software and try out the various options. I have found that, even on my slow DSL connection, I can upload a video to YouTube in the time it takes me to write the video’s description!


Visit the LearnMMD.com Homepage! Plenty of Mikumikudance instruction and info!


  1. Jade Houston Jade Houston
    October 20, 2017    

    I have started using prism like you said, but now that I have been using it for a while, Prism will no longer allow me to convert mmd renders. I receive a pop up that I have to pay to complete the action. What do I do? I have been using prism all this time (about a week) and i have enjoyed using it.

    • Reggie_Dentmore Reggie_Dentmore
      October 21, 2017    

      hmmm.. I am still using Prism 2.25… and whenever I open the program I do get a pop-up that asks if I am going commercial or just for my own non-commercial home use… I always click home use… and it lets me use it, no charge… it’s version 2.25 that I downloaded in 2014. I have no problems with it.

      • Jade Houston Jade Houston
        November 30, 2017    

        I will download that version then. I guess when I downloaded it I got an updated version.

        • Jade Houston Jade Houston
          November 30, 2017    

          When I download Prism, I automatically get version 3.05….I’m not sure how to get version 2.25 :/

          • Jade Houston Jade Houston
            December 10, 2017    

            I cannot seem to find your version anywhere! I’m not sure what to do. I have stopped rendering my motions because they lag if I try to play the file when the file is too large. Is there anything else I can do? Are you still answering questions?

            • December 10, 2017    

              What codec do you use to render your videos in the first place?

              • Jade Houston Jade Houston
                December 16, 2017    

                I use ffdshow to render my videos. It gives good quality but the file sizes are a bit on the large size. When i would convert with Prism, it would shrink the file without hurting the quality.

                • December 17, 2017    

                  I see. Well, in such case googling “prism old version download” should eventually give you something you can use.

                • Reggie_Dentmore Reggie_Dentmore
                  December 18, 2017    

                  Thank you, Jade… that’s my experience, as well… the final AVI file is much smaller but the quality seems to match the original. The smaller file size might come from the audio being shrunk into an Mp3 during conversion.

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