Crate rustyn64_audio 

rustyn64-audio — the Audio Interface (AI) DAC + sample-DMA path.

The RSP’s audio microcode mixes samples into an RDRAM buffer; the AI then DMAs that buffer out to the DAC at a programmable sample rate (set via the AI_DACRATE divider off the video clock) and raises an AI interrupt when a buffer starts playing (not when it drains — see Audio::write_reg). This crate models the AI side; the actual mixing is RSP microcode (in rustyn64-rsp), so under LLE the audio “falls out free” (ADR 0002).

The model follows the hardware description in n64brew_wiki/markdown/Audio Interface.md and the reference behavior in ares (ISC) ref-proj/ares/ares/n64/ai/: a two-deep DMA FIFO, the delayed-carry address bug reproduced as a 13-bit/11-bit split with a one-sample-deferred carry, the AI_LENGTH mirror on every write-only register, and a DAC that decays toward silence on underrun.

Part of the one-directional chip-crate graph (see docs/architecture.md): this crate does NOT depend on any other chip crate; it reaches RDRAM and the interrupt line through the AudioBus trait. #![no_std] + alloc.

Structs

Audio

Audio Interface state: the two-deep DMA FIFO, the DAC rate divider, and the derived-timing sample emission.

NeedsBus

Proof that a step needs the bus, produced only by Audio::tick_without_bus and consumed only by Audio::tick_with_bus.

StereoSample

One stereo output frame (interleaved signed 16-bit L, R).

Enums

AiIrq

The result an AI register write hands back to the Bus, which owns the MI interrupt lines the AI itself cannot name.

Region

The emulated console region, selecting the AI video clock.

Constants

MASTER_HZ

The canonical master clock (MASTER_HZ, ADR 0006), duplicated here because the chip-crate graph forbids rustyn64-audio depending on rustyn64-core.

VIDEO_CLOCK_NTSC

Video clock feeding the AI DAC divider on NTSC consoles (Hz).

VIDEO_CLOCK_PAL

Video clock feeding the AI DAC divider on PAL consoles (Hz).

Traits

AudioBus

The narrow bus the AI sees (RustyNES’s ApuBus analog): fetch a DMA sample word from RDRAM and raise the AI interrupt when a buffer starts.

Functions

version

Returns the crate version string.