The Famicom allows cartridges to modify the console’s audio signal between the APU (audio processor) and the TV. Most games don’t do anything with this capability, but some games included expansion audio chips on the cartridge board to enable enhanced audio beyond what the console is normally capable of.
This is the second of two followups to my post on the Sega CD PCM chip. Where the last post described a way to improve audio quality by applying an audio filter to final mixed PCM chip output, this post will describe an audio enhancement that improves audio quality by changing how the emulated chip itself generates samples.
This is a followup to the previous post on the Sega CD’s PCM sound chip. This post will start by going into more detail on why this chip’s audio output sounds pretty crummy by default, followed by one of two possible solutions that I know of to that problem.
In my last post I described an enhancement that an SNES or PS1 emulator can implement to improve audio quality in some games. Since then, I noticed that Sega CD games that use its PCM sound chip have pretty poor audio quality in my emulator - the audio output sounds very noisy and aliased.
It’s been a minute, and I haven’t done a whole lot of emulation work recently, but this is a topic I’ve wanted to do a short post about for a while: a really simple audio enhancement for SNES and PlayStation emulation that works surprisingly well with some games.
I recently added 32X support to my Sega Genesis emulator. While I’d say it was definitely easier than Sega CD overall, it wasn’t without difficulty, and much like Sega CD there’s very little public documentation aside from Sega’s poorly translated official docs from the 90s.
Sega released two hardware add-ons for the Genesis in an attempt to expand its hardware capabilities to enable more advanced gaming experiences. The first of these was the Sega CD, obviously a response to the PC Engine CD (which was fairly successful in Japan despite very poor sales in the rest of the world).
This is the fourth and final post in a series on the PlayStation SPU which will cover the remaining major features that were not covered in previous posts. This includes the noise generator (pseudorandom white noise), pitch modulation (dynamic pitch adjustment using another voice’s output), SPU IRQs (trigger IRQ when a specific sound RAM address is accessed), and the capture buffers (record recent samples from CD audio and two specific voices).
This is the third part in a series of posts on the PlayStation SPU (Sound Processing Unit). This post will focus on the SPU’s reverb feature, which can simulate echoes or reverberations. In short, it’s a much more advanced version of the SNES APU’s echo filter.
EDIT(2025-02-13): Much of this post is outdated, based on public documentation that has been updated since I wrote it. The envelope update algorithm in particular is inaccurate to actual hardware. Rather than delete the post, I’ll leave it up as-is and add another note up here if I ever get around to updating it.