OK rharv,

Apparently this MP3 rendering situation in RB has been around for a while! I found an old discussion from 2016, and you and Larry Kehl were going back and forth about it. Larry found a link to a Windows registry edit that enables the Fraunhofer codec!

Here is that previous thread ---- https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=352908&page=1

On page 2, he posted the link to a CMD file that you Run as Administrator ---- I just tried it, and it worked solidly! I'm on Windows 10 - 64bit, version 1809, and it worked like a charm, even though this patch was devised 5 years ago.

To recap my own situation, I had the LAME encoder installed a couple years ago, used with Audacity at first, then with Reaper. I installed BIAB just recently, and BIAB-64 worked fine, was able to save MP3. But not in BIAB-32 or RealBand 32. So I tried jford's suggestion of installing LAME ACM version, and then BIAB-32 worked fine(!) --- but still not in RealBand! I kept getting the error about the Stream Size. So I tried the CMD batch file, and now RealBand is also working fine for MP3. It allows me now to choose EITHER the LAME version, or the Layer-3 version (Fraunhofer which is already installed in Windows 10).

I didn't know about this being builtin, the 2 files are no doubt on every Windows 10 computer, they just need to have the registry settings enabled. Nice easy solution!

Jerry
2019 BiaB Megapack (634), RB 2019 (Build 4)
Reaper 5.983 x64, Audient id14 USB interface, Voicemeeter Potato 3.0.0.8, Nektar LX49+, Roland E20
i7-6700K Skylake desktop, 64bit Win10 Pro(1903), 32GB ram, 512GB system SSD + 2TB data SSD