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\\ SEGA 3D Classics interview – 3D Afterbunner II

PostPosted: Thu Jan 15, 2015 6:39 pm
by stalepie
Nice interview with M2 on the conversion of After Burner II (Arcade)'s music to 3DS: ... rn-part-2/

(Part 1 is

They talk about Mega Drive sound emulation as well, check it out:

MN: There’s one more point from the sound team about 3D After Burner II I want all the users out there to know about. We’ve implemented a low-pass filter for the first time in the “physical experience” game series in the 3D Remaster Project.

A “low-pass filter” is something we actually put into the Giga Drive* titles about halfway through. On 3D Altered Beast, we were working on the Mega Drive’s rather unique “DA,” a component of the PCM that sounds really rough and scratchy. When we got that working on the 3DS, though, it didn’t sound the way we were expecting.

* For more information about the Giga Drive, please refer to our previous blog posts: ... eloper-m2/

YO: We touched on it a bit during the 3D Altered Beast interview. For the first game, 3D Sonic the Hedgehog, it didn’t sound particularly off when we played it straight, but for 3D Altered Beast, Namiki-san said, “This won’t cut it.”

MN: Yeah. So I was thinking about how to go in and adjust that. For the FM sound source as well, I noticed that the emulated sound and sound that I recorded straight off an actual Mega Drive sound quite different.
Eventually, I implemented a low-pass filter. Simply put, it’s a filter that cuts out the high frequencies, and lets the low ones through. The audiophiles out there will understand, but by putting this in, it’s sort of like taking the “Tone” knob on a cassette player or an amp and adjusting the treble. As a result, I think we got closer to how the Mega Drive actually sounds.

NH: It made it much better.

MN: Only people on the development team heard what it was like before we put the filter in, so let me try to explain what the differences are to the users out there. When it wasn’t in, the treble was pretty strong and it sounded like things were almost too clear. Some people might feel that’s OK, but when you play the sound off a board and compare it to a recording off the 3DS, there’s a difference. By putting a filter on After Burner II, I feel like it’s much closer to the actual machine itself.

With the sampling frequency used on arcade boards from the After Burner II era, the ROMS back then weren’t all that large, so for things like distorted guitars, percussion sounds, or sound effects, they had to think about what level of sound quality they wanted. And while I think Hiro-shishou* probably put a lot of work into it, the sound quality possible on the original hardware, and the quality we can currently get through software simulation is quite different. So I think this is a worthwhile point of pursuit.

There is a soundtrack released by Wavemaster called AFTER BURNER 20th Anniversary Box. I think we’ve got the 3D After Burner II sound to a point where if you take the arcade version sound off that soundtrack and compare with sound from the headphone jack on a 3DS, you’ll think it was pretty close. I think it’s very close to the sound we recorded straight off the arcade board. I’m pretty happy with what we were able to do. The low-pass filter has some constraints on it, so we can’t use it everywhere we might want to, but it still makes a big difference.
* Hiroshi Kawaguchi, After Burner II’s original composer. ‘Shishou’ is a term similar to ‘sensei’ and denotes reverence.

SEGA 3D Classics - 3D After Burner II

- What exactly causes the output to change if you are faithfully emulating the FM sound source and bringing in the PCM data from the original chipset?

MN: The sounds are always converted to analog through the board’s circuitry, but the digital-to-analog converter and the wiring after that can have a pretty big differentiating effect on the sound. It can be a challenge to do this through software where you are replicating the analog circuitry due to CPU power restraints, even with the know-how we’ve built up. If you want to get very detailed, you’d have to emulate all the various components of the circuitry, such as the condensers and the individual resistors. We’re talking about silicon-level emulation here. So instead of all that, we tried 3DS’s pre-equipped low-pass filter instead.

- And you found that to be pretty effective, it seems. Not only where you able to achieve the sound quality you were looking for, but it sounds like you were able to revive two songs that had melodies through the internal sound source?

MN: Well, that story started with our director, Matsuoka, telling us that we were going to be emulating the music this time for After Burner II.

NH: It’s always better when a game’s file size is small*! This is something that our main programmer, Saito, worked himself to death over. If the file is really big, it eats up time during our own functionality checks. Saito exploded at one point saying, “That’s just unacceptable!” and demonstrated his prowess with a lot of optimization work, which ultimately saved us a lot of time overall.
*Streamed music results in a larger file size.

- It’s also nice for the consumers because it doesn’t eat up a lot of space on their SD cards.

NH: It certainly took more time to download 3D Galaxy Force II from the eShop compared to the other games in the series, so that was another reason Saito attacked this problem with a vengeance.