I was upmixing some stuff today and my own guide wasn't working.

Here are somethings I ran into:

AC3 file wouldn't load. I have no idea why, it might be that I need AC3.ACM updated or something, but GraphStudio threw an error.

The older version of the program GraphEdit had no issues. I opted to decode the 2.0 DD to WAV via BeLight (BeSweet). GraphStudio was fine with .wav audio.

The outputted AC3 file was unplayable. I finally checked the file with DelayCut (an AC3 file fixer) and pretty much the entire thing was frame errors. Once corrected the file played just fine.

The reason: newer versions of ffdshow encode improperly. The last "stable version", Beta7, while fairly old does produce errorless output.

So you may have to downgrade your ffdshow to make this work. I'll see if I can let the authors of the software know.