Genesis Plus GX, Where is the Audio Lowpass Filter?

[jnsl]

You were right, @hunterk… I had no idea that an absolute core path (not relative) was stored in the playlist. Thanks for the heads-up! All is fine now.

[butanebob]

Audio filter enables the low pass filter. Low pass filter % tunes the amount of filtering. A real megadrive console had a low pass filter on the audio so without it the audio is not correct but it does use up extra resources.

[Cyber]

@James-F

The values that matches the JAP Model 1 VA1 console is still 40 .

@James-F

A value of 45 will give you spot-on curve of Model1 up to 12kHz, from there the down slope begins. The default value of 60 is slightly more filtered than a Model2 would be, but a value of 55 is a better match, although the cuvres do NOT sit perfectly one on top of each other like the Model1 curves because GenPlusGX emulates 1st-order filter while Model2 has 2nd-order filter.

@lfan

What is the best setting to have the Model 1 sound?

Thanks!

@James-F

YM2612, Stereo, Low-pass, 55.

Which is correct to match the Model 1 Genesis, Low-Pass at 40%, 45% or 55%? It seems as if at one point you said 40%, then 45%, then at another time you said 55%.

@MarcoForce

The lowpass filter affects the CDDA audio of Sega CD in the real console?

@James-F

No.

I just noticed that this still occurs in the latest Genesis Plus GX core. The Sega CD PCM Chip’s output is also filtered leading to really muffled Red Book audio if the low pass filtering is enabled.

Of course disabling Low Pass Filtering will cause all FM Sound to be harsh and inaccurate so that’s not a solution.

Any chance of a fix for this?

Update:

I reported this behavior as a bug on the Genesis Plus Gx core GitHub and this is what ekeeke had to say,

" CD audio (CDDA + PCM) is indeed first mixed to MD audio (FM + PSG) then low-pass filtering is applied on the mixed stream, just like it is done on real MD hardware when you get the audio from the console A/V ouput.

You could however also get the audio from the CD unit L/R stereo outputs (using a cable connected to MD mini-jack output), in which case MD low-pass filtering only applies to MD audio, which is then mixed to CD audio in the CD unit.

Note that there is still low-pass filtering applied in the CD unit, just less stronger (there is a first low-pass filter on PCM and a second one at ~20KHz on the mixed audio stream before it goes out from L/R outputs).

Anyway, this is currently not emulated because it is more complex (the emulator and the library it uses for resampling is not really designed to apply mixing and filtering at different stages) and less optimized regarding CPU processing.

I left this issue open though as it would indeed be nice to have this option."