FF7/PSX/Sound/Opcodes/0xa8aa

0xA8 & 0xAA (Channel Volume & Pan)

0xA8 has 8-bit parameter, which used in calculation of base channel volume.

0xAA has 8-bit parameter, which used in calculation of channel pan (difference between left and right channel volume).

Understanding of this two opcodes isn't easy, but here is what I have got:

Volume Calculation

// Compiler optimizer (at least I think so :)) generated following tables to speedup volume calculation for left & right volume.

const uint16_t m_AKAO_VOLUME_TABLE_L[256] = {

   0x7f80, 0x7e80, 0x7d80, 0x7c80, 0x7b80, 0x7a80, 0x7980, 0x7880,
   0x7780, 0x7680, 0x7580, 0x7480, 0x7380, 0x7280, 0x7180, 0x7080,
   0x6f80, 0x6e80, 0x6d80, 0x6c80, 0x6b80, 0x6a80, 0x6980, 0x6880,
   0x6780, 0x6680, 0x6580, 0x6480, 0x6380, 0x6280, 0x6180, 0x6080,
   0x5f80, 0x5e80, 0x5d80, 0x5c80, 0x5b80, 0x5a80, 0x5980, 0x5880,
   0x5780, 0x5680, 0x5580, 0x5480, 0x5380, 0x5280, 0x5180, 0x5080,
   0x4f80, 0x4e80, 0x4d80, 0x4c80, 0x4b80, 0x4a80, 0x4980, 0x4880,
   0x4780, 0x4680, 0x4580, 0x4480, 0x4380, 0x4280, 0x4180, 0x4080,
   0x3f80, 0x3e80, 0x3d80, 0x3c80, 0x3b80, 0x3a80, 0x3980, 0x3880,
   0x3780, 0x3680, 0x3580, 0x3480, 0x3380, 0x3280, 0x3180, 0x3080,
   0x2f80, 0x2e80, 0x2d80, 0x2c80, 0x2b80, 0x2a80, 0x2980, 0x2880,
   0x2780, 0x2680, 0x2580, 0x2480, 0x2380, 0x2280, 0x2180, 0x2080,
   0x1f80, 0x1e80, 0x1d80, 0x1c80, 0x1b80, 0x1a80, 0x1980, 0x1880,
   0x1780, 0x1680, 0x1580, 0x1480, 0x1380, 0x1280, 0x1180, 0x1080,
   0x0f80, 0x0e80, 0x0d80, 0x0c80, 0x0b80, 0x0a80, 0x0980, 0x0880,
   0x0780, 0x0680, 0x0580, 0x0480, 0x0380, 0x0280, 0x0180, 0x0080,
   0x0000, 0xffff, 0xfffc, 0xfff7, 0xfff0, 0xffe7, 0xffdc, 0xffcf,
   0xffc0, 0xffaf, 0xff9c, 0xff87, 0xff70, 0xff57, 0xff3c, 0xff1f,
   0xff00, 0xfedf, 0xfebc, 0xfe97, 0xfe70, 0xfe47, 0xfe1c, 0xfdef,
   0xfdc0, 0xfd8f, 0xfd5c, 0xfd27, 0xfcf0, 0xfcb7, 0xfc7c, 0xfc3f,
   0xfc00, 0xfbbf, 0xfb7c, 0xfb37, 0xfaf0, 0xfaa7, 0xfa5c, 0xfa0f,
   0xf9c0, 0xf96f, 0xf91c, 0xf8c7, 0xf870, 0xf817, 0xf7bc, 0xf75f,
   0xf700, 0xf69f, 0xf63c, 0xf5d7, 0xf570, 0xf507, 0xf49c, 0xf42f,
   0xf3c0, 0xf34f, 0xf2dc, 0xf267, 0xf1f0, 0xf177, 0xf0fc, 0xf07f,
   0x1000, 0x1081, 0x1104, 0x1189, 0x1210, 0x1299, 0x1324, 0x13b1,
   0x1440, 0x14d1, 0x1564, 0x15f9, 0x1690, 0x1729, 0x17c4, 0x1861,
   0x1900, 0x19a1, 0x1a44, 0x1ae9, 0x1b90, 0x1c39, 0x1ce4, 0x1d91,
   0x1e40, 0x1ef1, 0x1fa4, 0x2059, 0x2110, 0x21c9, 0x2284, 0x2341,
   0x2400, 0x24c1, 0x2584, 0x2649, 0x2710, 0x27d9, 0x28a4, 0x2971,
   0x2a40, 0x2b11, 0x2be4, 0x2cb9, 0x2d90, 0x2e69, 0x2f44, 0x3021,
   0x3100, 0x31e1, 0x32c4, 0x33a9, 0x3490, 0x3579, 0x3664, 0x3751,
   0x3840, 0x3931, 0x3a24, 0x3b19, 0x3c10, 0x3d09, 0x3e04, 0x3f01

};

const uint16_t m_AKAO_VOLUME_TABLE_R[256] = {

   0x0080, 0x0180, 0x0280, 0x0380, 0x0480, 0x0580, 0x0680, 0x0780,
   0x0880, 0x0980, 0x0a80, 0x0b80, 0x0c80, 0x0d80, 0x0e80, 0x0f80,
   0x1080, 0x1180, 0x1280, 0x1380, 0x1480, 0x1580, 0x1680, 0x1780,
   0x1880, 0x1980, 0x1a80, 0x1b80, 0x1c80, 0x1d80, 0x1e80, 0x1f80,
   0x2080, 0x2180, 0x2280, 0x2380, 0x2480, 0x2580, 0x2680, 0x2780,
   0x2880, 0x2980, 0x2a80, 0x2b80, 0x2c80, 0x2d80, 0x2e80, 0x2f80,
   0x3080, 0x3180, 0x3280, 0x3380, 0x3480, 0x3580, 0x3680, 0x3780,
   0x3880, 0x3980, 0x3a80, 0x3b80, 0x3c80, 0x3d80, 0x3e80, 0x3f80,
   0x4080, 0x4180, 0x4280, 0x4380, 0x4480, 0x4580, 0x4680, 0x4780,
   0x4880, 0x4980, 0x4a80, 0x4b80, 0x4c80, 0x4d80, 0x4e80, 0x4f80,
   0x5080, 0x5180, 0x5280, 0x5380, 0x5480, 0x5580, 0x5680, 0x5780,
   0x5880, 0x5980, 0x5a80, 0x5b80, 0x5c80, 0x5d80, 0x5e80, 0x5f80,
   0x6080, 0x6180, 0x6280, 0x6380, 0x6480, 0x6580, 0x6680, 0x6780,
   0x6880, 0x6980, 0x6a80, 0x6b80, 0x6c80, 0x6d80, 0x6e80, 0x6f80,
   0x7080, 0x7180, 0x7280, 0x7380, 0x7480, 0x7580, 0x7680, 0x7780,
   0x7880, 0x7980, 0x7a80, 0x7b80, 0x7c80, 0x7d80, 0x7e80, 0x7f80,
   0x3f01, 0x3e04, 0x3d09, 0x3c10, 0x3b19, 0x3a24, 0x3931, 0x3840,
   0x3751, 0x3664, 0x3579, 0x3490, 0x33a9, 0x32c4, 0x31e1, 0x3100,
   0x3021, 0x2f44, 0x2e69, 0x2d90, 0x2cb9, 0x2be4, 0x2b11, 0x2a40,
   0x2971, 0x28a4, 0x27d9, 0x2710, 0x2649, 0x2584, 0x24c1, 0x2400,
   0x2341, 0x2284, 0x21c9, 0x2110, 0x2059, 0x1fa4, 0x1ef1, 0x1e40,
   0x1d91, 0x1ce4, 0x1c39, 0x1b90, 0x1ae9, 0x1a44, 0x19a1, 0x1900,
   0x1861, 0x17c4, 0x1729, 0x1690, 0x15f9, 0x1564, 0x14d1, 0x1440,
   0x13dc, 0x1324, 0x1299, 0x1210, 0x1189, 0x1104, 0x1081, 0x1000,
   0xf07f, 0xf0fc, 0xf177, 0xf1f0, 0xf267, 0xf2dc, 0xf34f, 0xf3c0,
   0xf42f, 0xf49c, 0xf507, 0xf570, 0xf5d7, 0xf63c, 0xf69f, 0xf700,
   0xf75f, 0xf7bc, 0xf817, 0xf870, 0xf8c7, 0xf91c, 0xf843, 0xf9c0,
   0xfa0f, 0xfa5c, 0xfaa7, 0xfaf0, 0xfb37, 0xfb7c, 0xfbbf, 0xfc00,
   0xfc3f, 0xfc7c, 0xfcb7, 0xfcf0, 0xfd27, 0xfd5c, 0xfd8f, 0xfdc0,
   0xfdef, 0xfe1c, 0xfe47, 0xfe70, 0xfe97, 0xfebc, 0xfedf, 0xff00,
   0xff1f, 0xff3c, 0xff57, 0xff70, 0xff87, 0xff9c, 0xffaf, 0xffc0,
   0xffcf, 0xffdc, 0xffe7, 0xfff0, 0xfff7, 0xfffc, 0xffff, 0x0000

};

left_volume = m_AKAO_VOLUME_TABLE_L[aa_parameter] * ((a8_parameter * 127 * 127) / 128) / 256 / 128;

right_volume = m_AKAO_VOLUME_TABLE_R[aa_parameter] * ((a8_parameter * 127 * 127) / 128) / 256 / 128;

I'll remove these tables in future and add normal mathematical interpretation of volume calculation.