MegaCD Redbook Audio Pop Issue
MegaCD Redbook Audio Pop Issue
My initial thought was that my game dump was corrupt, so i checked all the tracks checksum on redump.org (http://redump.org/disc/4104/) and all of the tracks matched the correct dump checksums. Just to be sure i also tried the dump with Kega Fusion and there was no audio popping there.
Then i tried the PAL version of the game, and still i was hearing the audio popping. So i went back to the original USA dump and tried playing the tracks with the BIOS audio CD player, still the same issue there.
But i did notice something weird, if i would rewind the track a few seconds the audio popping would go away. Below you can listen to a recording of what i was hearing when i would rewind the track a few seconds:
This is a list of the things i tried to find the source of this issue, some of them totally not making sense or related to the issue but just trying all of the options, without success and with the same result:
-Tried the analogue 3,5 mm output on IO board
-Tried the mini TOSlink output on IO board
-Removed the IO board and tried the HDMI audio output (48kHz and 96kHz)
-Enabled CD Audio filter in the core
-Switched between Model 1, Model 2 and Minimal Audio filters in the core
-Switched between YM2612 and YM3438 FM Chip in the core
-Enabled HiFi PCM in the core
-Loaded game from USB instead of SD card
-Tried another dump of the same game
-Tried another dump from another region of the same game
-Asked a friend to try the game on his MiSTer setup (he also experienced the same issue)
-Tried another PSU
-Tried another SD card
-Tried different BIOS versions of the MegaCD
-Minimal amount of USB devices connected to the USB board (1 controller only)
-Tried another DAC converter
-Tried another amplifier
-Played the same dump on Kega Fusion (no audio popping there)
-Converted BIN tracks to WAV and played it back on PC (no audio popping)
-Checked the checksums of the BIN files on redump.org (my dump matched verified correct dump values)
I googled and also read through all the MegaCD posts here but i couldn't find anyone else experiencing this. So i'm kind of lost why the audio popping occurs, something on my side or maybe something in the core. The audio popping only occurs with Redbook audio, all the other audio plays just fine.
The fact that by rewinding the tracks a bit the popping would go away makes me think that maybe it's a buffering issue but i might be totally wrong.
Does someone have some suggestions that i could try? maybe i'm overlooking something, thanks in advance.
EDIT: i've found some footage of somebody else with the same issue:
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Re: MegaCD Redbook Audio Pop Issue
Re: MegaCD Redbook Audio Pop Issue
Hey Fuzzy, thanks for confirming that the issue is not a local issue. I think i'll report this issue on the github repo of the MegaCD core, maybe the devs take a look at it.Fuzzy_Dunlop wrote: ↑Sat Mar 06, 2021 9:07 pm I've experienced the same issue with Ecco with the Mega CD core. Like you I tried switching audio output from HDMI, to analog to toslink and it was the same on all three sources. Unfortunately I don't have anything else to add, other than confirm your issue.
BTW, nice Wire reference with the nickname
![Laughing :lol:](./images/smilies/icon_lol.gif)
Re: MegaCD Redbook Audio Pop Issue
Obviously that doesn't help with your problem but I'll leave this here in case others have a similar setup to mine and wonder why MegaCD hitches like that... Doesn't cause problems with TGFXCD though which is strange.
Edit. The problem manifested just like yours though where rewinding or replaying a track would make the problem go away.
Re: MegaCD Redbook Audio Pop Issue
Could this be a new issue in the more recent cores, I've ran out of time today so can't test older ones.
Re: MegaCD Redbook Audio Pop Issue
I did try out some older versions of the core, the problem was still there. I could do a test run with all the versions released for the core when i've the time. In the meanwhile, i've reported the issue to the devs: https://github.com/MiSTer-devel/MegaCD_MiSTer/issues/80Blitzwing wrote: ↑Tue Mar 16, 2021 2:39 pm Well that's interesting. I've got two MiSTers one with the USB storage the other just the SD, they both have that exact hitching that you have, which is definitely different to the issue I worked around that I mentioned in my other post. I swear it wasn't there before.
Could this be a new issue in the more recent cores, I've ran out of time today so can't test older ones.
If more people chime in maybe they take a look at it.
Re: MegaCD Redbook Audio Pop Issue
Re: MegaCD Redbook Audio Pop Issue
One thing to try: does it persist if you convert the bin/cue to CHD? The chd library reads from disk in hunks so there's a bit of a memory buffer there. Wondering if that makes a difference.
I'll see if I can reproduce it myself.
edit: one other question. does it still happen if you just play redbook audio tracks from the bios cd player?
Re: MegaCD Redbook Audio Pop Issue
Thnx for your tips, tried some of it.zakk4223 wrote: ↑Wed Mar 17, 2021 10:31 pm Try different versions of Main too. Although from the video linked in the original post it predates any of the chd work. I never noticed it in all the testing I did during the chd work, but I wasn't really listening for it either. I wonder if it might be related to SD card speed?
One thing to try: does it persist if you convert the bin/cue to CHD? The chd library reads from disk in hunks so there's a bit of a memory buffer there. Wondering if that makes a difference.
I'll see if I can reproduce it myself.
edit: one other question. does it still happen if you just play redbook audio tracks from the bios cd player?
If I'm not mistaken CHD support was added since the 20210103 release right? Tried the releases from then on with my dump converted to CHD format (with the chdman tool from MAME, if you've another suggestion for converting tool let me know!) and the matching Main versions, the issue was still there.
Checked also some older versions of Main before CHD implementation, made sure the core was from the same period. Still the issue was there.
All of the above tested in bios cd player and in-game, with just one game tho (Ecco the Dolphin USA version). I'll try tomorrow with some other games, since previous tests with different core versions all had the most recent Main at the time of posting.
But good thinking on the SD card speed, right now I'm using a Sandisk SDXC Ultra 128GB Class10 UHS-1 card...do you think I should upgrade the card or is the reading speed (100 MB/s) sufficient?
Thnx again for your reply.
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Re: MegaCD Redbook Audio Pop Issue
Re: MegaCD Redbook Audio Pop Issue
MDFourier did a paper on the topic
http://junkerhq.net/MDFourier/notes/MDF ... Card-3.pdf
Here a more easier to read breakdown for people
https://www.retrorgb.com/mdfourier-sd-card-testing.html
Re: MegaCD Redbook Audio Pop Issue
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Re: MegaCD Redbook Audio Pop Issue
I thought it might be the SD card, but I've tried others, and have also tried loading the games from a USB hard drive. I usually use the optical audio out on the analog I/O board, and I tried using different DACs, but that didn't fix the problem. It also occurs over HDMI audio. I thought turning down the core or global volume down in the OSD might help, if the volume was too high and causing clipping, but that didn't seem to help. Within the Mega CD core, I have tried every setting possible, and I can still hear the cracks in the audio. I also upgraded to a 4 amp power supply, but that didn't help.
The problem only occurs with Redbook audio, and it's only with the Mega CD core. I don't have the same problem with other CD-based cores, such as TG-16 CD. After watching a lot of Youtube footage of this core running, it's hard to tell if everyone experiences this issue or not. I'm really not sure if its a core issue, or something with my setup.
There is also the possibility that original hardware is just supposed to sound like that. Maybe I couldn't hear the pops and cracks over the loud signal noise on original hardware, when I played Lunar 15 years ago. Maybe it's possible to hear the flaws with the clean audio signal that the MiSTer provides.
I was also reading a post on the Sega 16 forums, where some people noticed similar issues with real Sega CD hardware. There are some potentiometers that can be adjusted inside the unit, which apparently helped get cleaner audio streaming without cracks or pops. I have no idea if that same circuitry exists on the FPGA side of things, or if such a thing could be adjusted in a future core release.
Hopefully more attention is brought to this issue, and maybe the devs will take a look at it.
Re: MegaCD Redbook Audio Pop Issue
Speaking of which, how do I get to the BIOS CD player? Probably I need a different BIOS, I think I'm using a multiregion that starts the game with no chance to input anything, I wasn't able to make it open a player. I considered ripping a commercial CD to bin/cue to see what would happen. But I need to find my CD drive...
It sounds to me like a sync issue. In terms of audio, without knowing much under the hood of the original hardware or FPGAs, there seems to be potential for sync issues because Red Book audio is 44.1 while MiSTer's output and perhaps (probably?) the console's sound hardware run at a different sample rate.
If I understand correctly, with the original hardware the audio outputs of the Sega CD and Genesis hardware were combined as analog signals, which could have bypassed such a sync issue.
But this is speculation...
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Re: MegaCD Redbook Audio Pop Issue
The noise is measurable, that doesn't mean it's necessarily that perceptible however. The access noise is perceptible over analog audio on the analog IO board, but not perceptible over hdmi or optical audio. I remember hearing the SD access over analog audio when I had the Analog IO board, it is what it is. That's what I stopped using itdarksakul wrote: ↑Fri Mar 19, 2021 8:31 am I also think certain SD cards can cause noise on its own.
MDFourier did a paper on the topic
http://junkerhq.net/MDFourier/notes/MDF ... Card-3.pdf
Here a more easier to read breakdown for people
https://www.retrorgb.com/mdfourier-sd-card-testing.html
![Razz :P](./images/smilies/icon_razz.gif)
If the redbook audio popping by the OP is experienced over HDMI and optical, then this is probably unrelated to the thing in the MDFourier article.
I could potentially test to see if the issue is present on the mega everdrive on my original hardware with it's CD emulation as well. If it is I would assume it happens on OG hardware, but maybe not. Then I could see if I could burn a CD of ecco the dolphin to test on my jvc x'eye. I think I'm out of good CDs though.
Re: MegaCD Redbook Audio Pop Issue
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Re: MegaCD Redbook Audio Pop Issue
Re: MegaCD Redbook Audio Pop Issue
OP here, the audio popping is noticable on all outputs. Like described in the (long and messy) first post:aberu wrote: ↑Tue Jul 13, 2021 3:02 pmIf the redbook audio popping by the OP is experienced over HDMI and optical, then this is probably unrelated to the thing in the MDFourier article.darksakul wrote: ↑Fri Mar 19, 2021 8:31 am I also think certain SD cards can cause noise on its own.
MDFourier did a paper on the topic
http://junkerhq.net/MDFourier/notes/MDF ... Card-3.pdf
Here a more easier to read breakdown for people
https://www.retrorgb.com/mdfourier-sd-card-testing.html
It might be an OG hardware issue if the volume is above certain level, for example the manual of Terraonion's MegaSD cartridge says the following:-Tried the analogue 3,5 mm output on IO board
-Tried the mini TOSlink output on IO board
-Removed the IO board and tried the HDMI audio output (48kHz and 96kHz)
maybe in the core the levels are above 80%, and changing the volume on the Mister wont change this behaviour since it's tapping from the same (distorted and above 80%) signal.• CDDA audio volume: (default 80%) Allows setting the CD audio volume in the final mix.
• RF5c164 PCM audio volume: (default 80%) Allows setting the CD hardware PCM chip volume in the final mix. Both CDDA and PCM audio at 80% mimics the same audio volume levels as found on an actual Sega CD/Mega-CD unit. Setting them above 80% may lead to audio distortion.
If you are able to test it on your everdrive, or jvc unit, could you be so kind to test if rewinding the track for a seconds will make the issue go away for that track specifically?
Re: MegaCD Redbook Audio Pop Issue
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Re: MegaCD Redbook Audio Pop Issue
I usually use the optical audio out on the analog I/O board, and I tried using different DACs, but that didn't fix the problem. It also occurs over HDMI audio.
I thought turning down the core or global volume down in the OSD might help, if the volume was too high and causing clipping, but that didn't seem to help. Within the Mega CD core, I have tried every setting possible, and I can still hear the cracks in the audio.I also upgraded to a 4 amp power supply, but that didn't help.
The problem only occurs with Redbook audio, and it's only with the Mega CD core. I don't have the same problem with other CD-based cores, such as TG-16 CD. After watching a lot of Youtube footage of this core running, it's hard to tell if everyone experiences this issue or not.
I'm really not sure if its a core issue, or something with my setup.
There is also the possibility that original hardware is just supposed to sound like that.
Maybe I couldn't hear the pops and cracks over the loud signal noise on original hardware, when I played Lunar 15 years ago.
Maybe it's possible to hear the flaws with the clean audio signal that the MiSTer provides.
I was also reading a post on the Sega 16 forums where some people noticed similar issues with real Sega CD hardware.
There are some potentiometers that can be adjusted inside the unit, which apparently helped get cleaner audio streaming without cracks or pops.
I have no idea if that same circuitry exists on the FPGA side of things, or if such a thing could be adjusted in a future core release.
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Re: MegaCD Redbook Audio Pop Issue
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Re: MegaCD Redbook Audio Pop Issue
I just tried it. Exactly the same popping issues. Very noticeable on the Keio Flying Squadron title screen and the "zoom into town" intro in Lunar. I really hope this gets fixed someday. Thank you very much for trying.
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Re: MegaCD Redbook Audio Pop Issue
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Re: MegaCD Redbook Audio Pop Issue
Thanks for following up with them. I just hope it's something that isn't difficult to fix.aberu wrote: ↑Sun Jul 10, 2022 3:18 pm After discussion with Zakk and Kitrinx it appears the buffer could be the cause of this, there is a mismatch in the timing of the fill of the buffer and the dump of the buffer, leading to occasional gaps. At least, that's likely what is happening, but we don't know for sure.
Re: MegaCD Redbook Audio Pop Issue
Was there any development on this issue? Just tried Ecco and indeed, the popping is there. Compared to some examples posted above, the popping seems to be less frequent and not as loud, although definitely still there. Tried the BIOS CD player, same deal.
Re: MegaCD Redbook Audio Pop Issue
Yes, but the sound effects make it harder to notice. Going into the gameplay and staying still while only the music plays or playing the music trough the bios CD player is the best way to tell, listening with headphones at a decent volume will make it more noticeable. It is not as loud or as frequent as some of the old examples posted above, at least for me. The longer the music plays, the popping becomes less frequent until it seems like it stops. The same behavior happens both ingame and BIOS cd player. The first 10-15 seconds of any track seem to be the worst.