Is it possible to change GMOD Voice codecs?

Is it possible to change GMOD Voice codecs? GMOD Uses some outdated codecs to send/decode voice resulting in a terrible voice quality.

I have seen so much youtubers making some videos which didn't work at all.

Unfortunately, no. The voice codecs are hard-coded into the engine itself. In order to change it, you would need full engine license access (which costs several thousands of dollars), and even so, it's very difficult to replace it in the code.

There were convars for that (both gmod and tf2), but after the steampipe update it disappeared.