MiSTer FPGA Forum

There appears to be some confusion by some people in the community why unfiltered Mega CD redbook audio was implemented, so I hope to clear up any confusion.

Its pretty simple, a real Mega CD unit could output redbook audio either filtered through the Genesis/Megadrive headphone out, or unfiltered through the Mega CDs RCA jacks with the patch cable, so this change is technically still accurate representation of how Mega CD audio was heard as long as you used the patch cable and Mega CDs RCA Jacks.

To be clear, you can still filter the FM audio in the core, its only the actual CD redbook audio that will be unfiltered. I do believe that an option to filter CD audio should be implemented as well, but that can always come later.

Hope this helps with any questions about this commit.

Did the RCA jacks only output CD Audio, or did they handle the Mega CD's PCM too?

FoxbatStargazer wrote: ↑Sun Jan 31, 2021 2:43 pm Did the RCA jacks only output CD Audio, or did they handle the Mega CD's PCM too?

Both I believe. Basically the the patch cable grounds the pins on the Sega CD's expansion connector that would feed audio to the Genesis. So instead the Sega CD's own audio gets fed straight to the audio jacks without any filtering and the actual FM audio from the Genesis comes through the jacks as is.

Also, another cool thing about using the patch cable is you can balance the FM audio to your liking using the Volume Slider on the Genesis. So if you wanted less FM and more CD audio you could just lower it.

Also, anyone who says this change is a regression, wrong or broken is misinformed.

A real Mega CD came with both the patch cable and RCA cables. This is how Sega intended for people to hook up their Genesis to a Mega CD. Those who didn't use the patch cable and just ran all audio out from the headphone jack were simply not taking full advantage of Mega CD CDDA audio, it was never meant to be so heavily filtered, just the FM side was. All this change does is make Mega CD audio sound the way it was intended.

I do believe a filter toggle should be provided for those who want degraded CDDA audio, but kinda getting annoyed of people telling me my feature request that Sorg implemented was wrong. The only reason Sega even allowed CDDA audio to passthrough the headphone jack was simple, so you can hear the CD audio while wearing headphones.

Edit: Found this scanned page of the official Sega CD manual proving this is how Sega intended people to hook up their Sega CDs to a stereo TV.

Thank you for getting this pushed thru. I was one of those kids that saved up my Summer working money for a stereo system and I used the AV cable

Great news if you didn't see it, Sorg updated the Mega CD Core with a separate filter toggle for CD audio, so now you can have redbook audio either filtered or unfiltered, so everyone should be happy now.

This is the way. Thank You Sorgelig.

I found a bug that might be related to this change? I thought this was working before but isn't now anyway.

In Sonic CD (US), certain soundfx are not playing no matter the audio settings. For example, running and then pressing down to spin on the ground is silent, as is the sound when you lose a shield from getting hit. There's also something missing from the time travel sfx. Most other sfx and music are still working though.

FoxbatStargazer wrote: ↑Thu Feb 04, 2021 4:48 pm I found a bug that might be related to this change? I thought this was working before but isn't now anyway.

In Sonic CD (US), certain soundfx are not playing no matter the audio settings. For example, running and then pressing down to spin on the ground is silent, as is the sound when you lose a shield from getting hit. There's also something missing from the time travel sfx. Most other sfx and music are still working though.

Can you test a prior build. See if this is a new bug. I'll test the recent build.

I'm gonna put the last 4 official builds on my SD card and see when this bug started.

FoxbatStargazer wrote: ↑Thu Feb 04, 2021 4:48 pm I found a bug that might be related to this change? I thought this was working before but isn't now anyway.

In Sonic CD (US), certain soundfx are not playing no matter the audio settings. For example, running and then pressing down to spin on the ground is silent, as is the sound when you lose a shield from getting hit. There's also something missing from the time travel sfx. Most other sfx and music are still working though.

I think this is normal behavior. Time Stamped from the 360 port.

https://youtu.be/qQwZFLwjeUw?t=278

There is no rolling sound.. it is meant to be... .

It is normal.

Ugh, sorry for the false alarm. I even owned this game back in the day alongside the genesis ones, and never recall noticing a difference! Too taken in by that redbook audio I guess...