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Atari 5200 sound issues in Atari Flashback Classics 3

Posted: Tue Jan 08, 2019 12:09 am
by Justin42
Hi-- just wanted to report about sounds issues in the Atari 5200 games. First off, I'm thrilled that the 5200 is finally represented in these collections-- it was my first game system (bought in 1982) and I'll have a soft spot for it. So I really hope I can help get things 100% right because they're SOOO close! Final Legacy's theme music is entirely off-key, and various little sound effects in some games are just off (like the crowd noise between innings sounds totally weird, I remember it being a pretty good white noise approximation of a crowd-- listen to ). I never played Countermeasure enough to know what it sounds like for sure. Centipede's shooting sound is SLIGHTLY wrong-- it's really close but not quite right. Little things like that.

(I first got it on the Switch but also picked up the PS4 version this weekend to compare and it's doing the same thing-- I assume the emulators you're using are the same on each platform, basically)

I've been trying to search for authoritative documentation about this issue but I've been drawing mostly a blank, so I might not have the details 100% right. But basically, the Atari 5200 (and its ROM) was based on the Atari 400 computer, which used Atari "OS A". When you'd play *some* 5200 games on Atari XL/XE systems (which used "OS B" or "OS C") the sound would be off-key -- in much the same way your games are. I believe the memory location for some of POKEY's data was moved between the OS revisions so it's not getting the right channels in the right places, but I don't know the specifics. It's sort of like you're using the Atari XE or XEGS ROM in your 5200 emulator, although I am unable to reproduce exactly the same off-key sounds. But for example, this video shows how the Final Legacy theme should sound:

As an example of what the Atari 400/800 and XL/XE discrepancy sounds like on a game, please listen to this video of the Atari 5200 Gremlins game intro: . Then, listen to it played on an Atari XL/XE system: -- the "bom - bom- bom - bombombombom - bom - booooom - bom -bom" sound is totally wrong and sounds like chains rattling or something. This is VERY similar to how the 5200 games sound in Flashback Classics 3-- there's like a POKEY effect that doesn't work right with the wrong OS. They're not off-key in the same way that the XL/XEs were off key, so I'm not entirely sure what's going on, but there's SOMETHING sending the POKEY bad data. I'm wondering if perhaps there were 2 5200 BIOSes for the 4-joystick (original) and 2-joystick (updated) models, or something?

All that said, these specific issues on these games with the XL/XE having sound issues and needing OS A so maybe I'm overthinking this and it's just an emulation glitch in general with POKEY. I'd just really like to hear this perfectly! It's so close I understand if it's too minor to fix but I'm really hoping it might be an easy fix-- like the distortion bits in POKEY are being handled slightly wrong or something?

If I can help with this any more or you need more examples or anything, please let me know. Again, I really love the Flashback collections (especially the Switch one to have everything on one cart!!) and just want to see them absolutely perfect!

Re: Atari 5200 sound issues in Atari Flashback Classics 3

Posted: Fri Feb 01, 2019 2:37 pm
by CodeMystics
The discrepancy was unrelated to the BIOS but we were able to track it down. It's our hope to have the patch released soon.

Thanks for the detailed feedback. It was a great help!

Re: Atari 5200 sound issues in Atari Flashback Classics 3

Posted: Tue Feb 05, 2019 2:04 pm
by Justin42
Wow, fantastic! I'm really looking forward to hearing it! Thanks for looking into this :)