3DS PDN

For Developer Only

People for the longest time have wanted to play mp3(s) while games are running. Up until now, it was unknown whether this was possible, but as it turns out it is possible to do this.As anyone who has developed for 3ds before, should know that 3ds has two ways of playing audios, one through CSND and one through DSP. Apparently, it is possible to use CSND with modules to play music.

Attached is a functional POC of the music player, it just plays a mp3 off your sd card. You need to put a mp3 file named as 'sound.mp3' on the root of your sd card and then enable game patching. I rewrote the PDN sysmodule, so now it spawns a thread in appcore for mp3 decoding and playing.

The POC works (atleast on n3ds, for o3ds you might need to change appcore to syscore or change the prio) but not smoothly, every time the system/game spawns a new thread there is a small break in audio due to the audio thread freezing and there are constant "pop" sounds. My guess is the audio decoding and playing code will need soft-tuning(do note I'm not the best when it comes to audio stuff).

Notes:

• Please remove patches for any other sysmodule before trying this as they can cause issues.
• It might be better if we do not use PDN for our purposes but create a entirely new sysmodule which will be launched by the homebrew audio player app.
• 3ds sleep mode will be broken by this, you'll need to restart your console.
• On a n3ds, enabling "Clock + L2C" seems to make the code run a bit more smoother.

I hope the scene will be able to work its magic and fix the issues my POC has and then incorporate the code in other homebrew audio players!

Also if you test this and if this works/does not work for you, please let me know!