Difference between revisions of "APU"
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== Global Processor (GP) == | == Global Processor (GP) == | ||
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| + | The GP runs all enabled sound effects on the voice bins. DirectSound allows to load custom DSP code for these effects. | ||
* GPS = GP Scratch (?) | * GPS = GP Scratch (?) | ||
Revision as of 10:51, 26 June 2017
The MCPX contains an APU (Audio Processing Unit).
- SSL = Stream Segment List
- SGE = Scatter Gather Entry
- PRD = Physical Resource Descriptor (Same thing as SGE?!)
Contents
Global Processor (GP)
The GP runs all enabled sound effects on the voice bins. DirectSound allows to load custom DSP code for these effects.
- 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.
- EPS = EP Scratch (?)
- EPF = EP FIFO
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:
- Head-related transfer function
- Low-frequency oscillation
- Pitch
- Input type (8bit, 16bit, 24bit, ADPCM)
- Volume envelope
- 8 target bins, each with a custom volume for this voice
There are 32 bins which these voices will be mixed into.
Memory sections
- 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
