Hello there.
I know that GG's video player only supports WMV file formats.

Well, I got a Full HD MP4 video that I can't play in it. And in any way I convert the video to a .WMV it loses A LOT of quality and becomes ugly.

Any suggestion about keeping the quality?

This link list a few of the aps that can do this for you.

https://en.wikipedia.org/wiki/Windows_Media_Video

Hum... I'm asking how to keep the video quality and you link the Wikipedia page about WMV?
I already converted the video, but the quality in GG is so poor.

And I must keep the FHD.

I guess the point would have been to find a program that will make a high quality WMV file in the newest format they have. That should keep the quality. So they say.

Inside Game Guru the video will attempt to go to your full screen resolution.
As far as I know, if the video is not trying to stretch to a size bigger then it was compressed at, it should be close.

WMV is not my favorite format and I usually have to try a few time to find a happy medium. I have not tried to make a full HD size video in WMV format. I have tried with the screen size shown below in my sig.

Give Lee an email lee@thegamecreators.com and see if he has any suggestions for why you are losing quality in your video when displayed in Game Guru.

Yep, the real question was: is there a way to play a different format in GG, or a free way to convert without quality loss?
I only found commercial apps that do it.
I guess it's the only way for now.

Sorry. WMV format is the only one in Game Guru right now. Hopefully one day we may have other formats.

The only free encoder they listed was this one.
VSDC Free Video Editor

EDIT:
For 1080P size they suggest 10mbits/second data rate.

That is a lot of data to play.

Did you tried this one?

3com

Yes, I tried many apps. But mostly commercial, for FHD conversion.