Garbled Audio on Sega CD Core via MiSTer Pi's Analog Audio Out [Solved]

[daryl_fb251]

Hello everyone, I posted the same message below in the Mister Discord but would love to get answers/feedback where I can

Hey there Just wanted to ask if mangled audio on the Sega CD core is a known issue?

I've got a Mister Pi and when I run certain Sega CD games, the audio via the headphone jack gets garbled. The same audio when running through the HDMI cable is clear and ungarbled, as you would expect.

Just wanted to ask here if this is known and if not, how should I report it?
example, Lords of Thunder, ran from SD or USB, whether compressed using CHD or as a raw bin/cue dump, delivers garbled audio through the Mister Pi's headphone jack (the one near the VGA out) but delivers perfect audio via HDMI. Same for Keio's Flying Squadron and Robo Aleste.

EDIT: SOLUTION! The garbled audio can be fixed by switching on the core's Composite Blend feature. This is found in the Audio/Video settings of the core.

2nd Edit: I removed a sentence that claimed that it is the MegaCD core being incompatible with the 9.2 AV board. This was based on Taki's response, but other users have reported that the MegaCD core works fine when not using other non-MisterPi boards with the 9.2 AV board.

[limi]

Possibly viewtopic.php?p=90780#p90780

[daryl_fb251]

Cheers Limi!

While it may be possible that Taki's IO board might be the issue, the headphone jack works perfectly on every other core I have tried.

It is only the SEGA CD core that has this issue.

Lords of Thunder on the TGFXCD core works perfectly too. I know they are different games for different systems etc but it shows that the issue is likely to be the MegaCD core itself.

1) If someone reading this has the Mister Pi triple stack, could they test the analog audio out using a MegaCD version of Lords of Thunder and report back?

2) If this issue was an issue with the core, who and where would I report it to?

[daryl_fb251]

I managed to find a similar report regarding the PSX core using the Mister PI:

https://www.reddit.com/r/MiSTerFPGA/com ... t/ls0x684/

The sound garbling present in the video on this thread is similar to the garbling I am experiencing. I'll test the Tony Hawks Pro Skater games tonight to see if that produces the same results on my build.

The PSX core has been fine on my build through Analog and a lot of the Sega CD games work without issues too, but Keio, Lords of Thunder, Robo Aleste create the issue.

A comment on this thread reports that the issue is present on PSX and SegaCD cores through the Mister Pi.

I'm assuming there are no issues regarding analog audio on regular, non-Taki IO boards as I can't find any posts or info about this issue.

[daryl_fb251]

Tony Hawks Pro Skater 2 (the PSX game with garbled audio from the Reddit post) works fine on my Mister Pi build, there is no garbled audio.

I tried using 5 older MegaCD versions of the cores but none of these actually booted on my Mister. Only the most recent version one boots, and the garbled audio remains.

I'm happy to live with this limitation (if I must play these games with non garbled sound I can use HDMI) but I'll try and get in touch with Taki to let him know my findings.

[daryl_fb251]

I spoke to Taki and he responded by saying that garbled audio is a known issue on the PSX and MegaCD cores because these cores are not compatible with the AV I/O 9.2 boards, meaning that this also occurs with DE10s etc when used with the 9.2 board. The reason being that cores were designed before the AV 9.2 board was created.

While this is nice to know, I actually found a solution to the MegaCD garbled audio issue: Switching the core's Composite Blend feature to On sorts out the audio. The audio is perfect, with the obvious caviat being that the visuals are being viewed through the composite blend feature.

I'll update the first post with the important info, but as far as I'm concerned, the problem is solved until the core is changed to work with the AV 9.2 board.

Happy gaming!

[aberu]

That explanation doesn't make any sense to me. The framework update that would have to do with compatibility with that board all happened over 6 months ago, and the MegaCD core is updated already.

https://www.reddit.com/r/MiSTerFPGA/com ... /?sort=new

Someone already RMA'd it because their capacitor values were wrong, which is the same thing that Ricardo mentioned in the thread linked by limi above.

[dickhardpill]

I don' recall any problems with the MegaCD or PSX core and I have been using the 9.2 analog IO

[daryl_fb251]

That explanation doesn't make any sense to me. The framework update that would have to do with compatibility with that board all happened over 6 months ago, and the MegaCD core is updated already.

If it's any consolation, Taki's explanation it didn't make sense to me either. Why switching to composite blend (a visual option!) fixes the issue is also a head scratcher, but it's a fix so I won't complain.

https://www.reddit.com/r/MiSTerFPGA/com ... /?sort=new

Someone already RMA'd it because their capacitor values were wrong, which is the same thing that Ricardo mentioned in the thread linked by limi above.

However, the issue I experienced is not the same as the one in the linked thread. The linked audio examples from the reddit post (Hydrocity stage from Sonic) demonstrates muffled audio as opposed to garbled, crackly audio which I was experiencing. Plus, this was only happening on the MegaCD core on my setup.

The point of this thread was to find a fix or other instances for the garbled audio produced by the Analog Audio out when using the MegaCD core. I let Taki know that this was an issue because he might have needed to know. I paraphrased his response but it is true to his original reply.

[daryl_fb251]

I don' recall any problems with the MegaCD or PSX core and I have been using the 9.2 analog IO

Legitimately curious, are you using a MisterPi?

Also, if you are interested in helping, could you try Popful Mail on the MegaCD? That has garbled audio from the opening cutscene.

[dickhardpill]

I don' recall any problems with the MegaCD or PSX core and I have been using the 9.2 analog IO

Legitimately curious, are you using a MisterPi?

Also, if you are interested in helping, could you try Popful Mail on the MegaCD? That has garbled audio from the opening cutscene.

No and I apologize for not specifying, I meant to do so in my original post.

[daryl_fb251]

I don' recall any problems with the MegaCD or PSX core and I have been using the 9.2 analog IO

Legitimately curious, are you using a MisterPi?

Also, if you are interested in helping, could you try Popful Mail on the MegaCD? That has garbled audio from the opening cutscene.

No and I apologize for not specifying, I meant to do so in my original post.

No worries! It does appear to be MisterPi issue then, or at least my MisterPi

[dammodayu]

I managed to find a similar report regarding the PSX core using the Mister PI:

https://www.reddit.com/r/MiSTerFPGA/com ... t/ls0x684/

The sound garbling present in the video on this thread is similar to the garbling I am experiencing. I'll test the Tony Hawks Pro Skater games tonight to see if that produces the same results on my build.

The PSX core has been fine on my build through Analog and a lot of the Sega CD games work without issues too, but Keio, Lords of Thunder, Robo Aleste create the issue.

A comment on this thread reports that the issue is present on PSX and SegaCD cores through the Mister Pi.

I'm assuming there are no issues regarding analog audio on regular, non-Taki IO boards as I can't find any posts or info about this issue.

I was the OP of this thread on Reddit
I ended up using a DAC, which solved my audio problems.