APU

The MCPX contains an APU (Audio Processing Unit).

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

Global Processor (GP)

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

Encode Processor (EP)

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

Voice Processor (VP)

• VPV = VP Voices
• VPSGE = VP SGEs
• VPSSL = VP SSLs

Voice lists

• 2D
• 3D
• MP

Voice structure

This is 0x80 bytes

Pitch calculation

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

Related

• ACI
• DSP
• Xbox ADPCM
• Script to inspect APU registers and voice buffers (See master revision for updates)