nolibgs_hello_worlds/hello_spu_readback

This example is adapted from PsyQ's sample : psyq/psx/sample/sound/CDVOL, main.c,v 1.14 1997/05/02 13:05:21 by ayako. It was edited to fix typos, have a hopefully better code organization with hopefully more usefull variable names.

What it does is demonstrate how to transfer data from the PSX 's SPU to main memory in order to analyze / process the audio signal and dostuff accordingly.
In this instance, it's used to determine the coordinates of a few primitives to display a VU-meter.

This technique is known to be used in certain games for lipsynching or audio visualization ( Crash team racing, Hercules, Vib Ribbon ...).

pcsx-redux : no animation

Pcsx-redux does not yet support these specific SPU buffers nor triggerring IRQ from them so as of 11-2021 this example doesn't work in this particular emulator.
If looking for an alternative, check duckstation out.

PsyQ's SpuReadDecodedData() doc errata

The main function for transferring data from the SPU to the RAM is SpuReadDecodedData(), and is documented in LibRef47.pdf, p1054.
The table on this page (Table 15-2) contains erroneous data and should read :

The correct address ranges for the SPU buffer is :

Map (bytes)	Data contents
0x000 - 0x3ff	CD Left channel
0x400 - 0x7ff	CD Right channel
0x800 - 0xbff	Voice 1
0xC00 - 0xfff	Voice 3

Compiling

You need mkpsxiso in your $PATH to generate a PSX disk image. Typing

make

in a terminal will compile and generate the bin/cue files.

Typing

make cleansub

will clean the current directory

More on CDDA

See the hello_cdda example in this repo.

Docs and links

Original psyq example : psyq/psx/sample/sound/CDVOL, main.c,v 1.14 1997/05/02 13:05:21 by ayako

Music credits

Track 1 : Beach Party by Kevin MacLeod Link: https://incompetech.filmmusic.io/song/3429-beach-party License: https://filmmusic.io/standard-license

Track 2: Funk Game Loop by Kevin MacLeod Link: https://incompetech.filmmusic.io/song/3787-funk-game-loop License: https://filmmusic.io/standard-license