world4utau update


Teto's Territory
Defender of Defoko
It's out!
I've updated world4utau with the latest software.

Feel free to download it here:

There are a few things you need to take note of when using this version of world4utau (w4u).

First, w4u will rely partially on .frq files. So please ensure they have been generated beforehand.
A personal tip from me:
Please do not use SpeedWagon to create .frq files if your voicebank is a power-scale one.
Use fresamp or resampler10 instead.

Next, w4u will produce three files, ".dio", ".ctspec" and ".d4c" when rendering.
This is similar to the original w4u but is slightly different since the ".ctspec" and ".d4c" files are the replacement for ".star" and ".platinum" respectively.

These files are generated automatically the first time you use w4u as a resampler. They work similar to moresampler's .llsm to speed up the rendering. You may delete them but it will slow down the rendering significantly since re-generating the files take a long time.

The ".dio" files, however, are still the same and are still compatible with nmasao1's frqeditor plugin.

I also ported a few flags from other resamplers.
· R flag
Use this flag to regenerate .dio, .ctspec and .d4c files
Advisable to use after editing .frq files.
Works similar to TIPS R flag.

· B flag (0~100 def50)
Breathiness flag ported from other resamplers.
Will function similar to WARP's B flag for values below 50.
Retains tn_fnds's B flag for values above 50.

· O flag (-100~100 def0)
One-to-one port of tn_fnds's O flag
Change the voice "brightness". Specifying + values suppresses lower frequencies and amplifies higher ones.

This next part is quite important.
The default method of lengthening notes in w4u is stretching. I.e. world4utau is a stretching resampler

However, I implemented a loop system into w4u which you can activate using the e flag.

· e flag
Changes the rendering method from stretching to looping.
This is the opposite of tn_fnds.
By using the e flag, long notes may sound smoother.

Take note that, although I took reference from tn_fnds and EFB-GT when creating the loop based system, it was made with w4u's code in mind so the loops may not be as smooth since it is not a direct port.

The output of world4utau is similar to EFB-GT but the rendering time is around 10 times longer (averaging first time use and subsequent uses).
Then you may ask, why use world4utau?
Here are some reasons:
1) Better noise reduction. EFB-GT has engine noise while world4utau barely has any.
2) Slightly more accurate frequency estimation, comparable to moresampler's. It is also editable using nmasao's frqeditor.
3) The flags, especially the g flag. The one in EFB-GT does not do formant conversion (gender change)
4) It is a stretching resampler which makes it a good resampler for other language VBs that aren't Japanese. I also believe that world4utau's stretching is better than tn_fnds's.

I am also releasing another world4utau edit.
I call this creation worldend4utau AKA wn4u

Dl link here:

I am releasing this resampler as a proof of theory type of thing. In general, most suggestions to make a resampler is to port the latest WORLD one-to-one as a resampler. In theory, it seems good but I believe otherwise.

wn4u has a way longer rendering time than w4u since it uses HARVEST for its F0 estimation.
So take note that it produces ".harvest" files instead of ".dio".

HARVEST is a good F0 estimator but it is not suited to be used in a UTAU resampler (in my opinion) due to how long it takes to estimate F0. There are also a few other flaws as well which I noticed when creating young3.

But hey, that's just my opinion! Feel free to try out wn4u.
In general, wn4u will produce slightly more realistic vocals than the w4u update above due to the fact it uses the latest d4c algorithm. (I used conventional d4c for w4u because I felt it was more robust)

Due to this reason, I added an additional flag, n (case sensitive)

· n flag
Use only if synthesized output sounds bad.
Will convert aperiodicity approximation back to conventional one.
Take note that this will automatically activate the R flag.
Use only on specific notes.

Other than that, wn4u is identical to w4u.

Warning, using worldend4utau (wn4u) will overwrite world4utau (w4u)'s .d4c and .ctspec files, vice versa.
That is why I am releasing wn4u with a password. The password is young3

That's that. Thank you for reading this long post. Have fun!
Last edited:


Ruko's Ruffians
Defender of Defoko
You can't understand how happy I am that you've released an update to W4U. I've been looking forward to this for a very long time. Thank you!
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Teto's Territory
Defender of Defoko
Thread starter
You can't understand how happy I am that you've released an update to W4U. I've been looking forward to this for a very long time. Thank you!
Likewise, I am really grateful that you commented on this post! I was rather doubtful of releasing this update so if it made you happy, then I too am happy as well! Thank you!


Teto's Territory
Defender of Defoko
Thread starter
Adjusted world4utau to rectify a bug. There was an error where w4u will cause end notes to go off tune.
Please redownload and use R flag on those notes.


(This is the same link as above)

Feel free to contact me at my twitter @UtauZany for any other queries.
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Teto's Territory
Defender of Defoko
This version only compiles on Windows, on other systems you get world.h:17:10: fatal error: windows.h


Teto's Territory
Defender of Defoko
Thread starter
I've been trying to remove the windows.h dependencies but the results are unsatisfactory (likely to be a bug on my end). I am just a hobbyist coder so I am sorry if I can't meet anyone's cross-platforming needs.

TLDR: Until I find the time and knowledge, this version of w4u will remain windows only.
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Teto's Territory
Defender of Defoko
Hello! I know I am months late to the party but I really love the sound of this resampler!

I'm curious to know whether any plans to implement other flags are in place (mostly thinking of the A flag which is amplitude modulation; translates pitch to amplitude which is good for dynamic vibratos)

If not I may eventually fork this but I don't even know what programming language this is in yet (haven't checked) and C/C++ scares me (though i worked in it before for university so i'm sure it's not something i'd find too hard to pick up?)

I love this though, honestly. Great work! One of my best friends swore by Young3 and I feel like this one sounds even better?

Edit: I'm not a fan of how this resampler sounds on my own vb; it's more buzzy and grainy than young3 and other resamplers and i'm hearing a lot of artifacting. Though, with that being said, it sounds nothing like any other resampler thus far so I'm excited to hear about any updates to this! As you're just a hobbyist programmer I won't throw a bunch of ideas at you, but i will send you best of luck hoping that this resampler can keep moving forward! it seems awesome!
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