APU

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Revision as of 16:18, 26 June 2017 by JayFoxRox (talk | contribs) (Voice Processor (VP))
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The MCPX contains an APU (Audio Processing Unit).

  • SSL = Stream Segment List
  • SGE = Scatter Gather Entry
  • PRD = Physical Resource Descriptor (Same thing as SGE?!)

Voice Processor (VP)

A powerful voice processor. There can be up to 256 voices[citation needed] and 64[citation needed] of those can be 3D.

Per-voice settings:

There are 32 bins which these voices will be mixed into.

Related APU memory

  • VPV = VP Voices
  • VPHT = VP HRTF Target
  • VPHC = VP HRTF Current
  • VPSGE = VP SGEs
  • VPSSL = VP SSLs

Voice lists

The voices are kept in a single-linked list. There are 3 voice lists:

  • 2D
  • 3D
  • MP (Multipass?)

Voice structure

This is 0x80 bytes

Pitch calculation

The 16 bit signed pitch value (p) can be converted to and from a unsigned frequency in Hz (f) using the following formulas:

p = 4096 * log2(f / 48000)
f = pow2(p / 4096) * 48000

Global Processor (GP)

The GP runs all enabled sound effects on the voice bins. DirectSound allows to load custom DSP code for these effects.

The GP DSP seems to run at 160 MHz

Memory map

Related APU memory

  • GPS = GP Scratch (?)
  • GPF = GP FIFO

Encode Processor (EP)

The EP encodes the final AC3 stream for SPDIF. [FIXME] It is not used during the Boot Animation.

Memory map

Related APU memory

  • EPS = EP Scratch (?)
  • EPF = EP FIFO

Related