DFPlayer Mini - PCB Schematics - Decode MP3

Using Arduino Audio
1

Does anyone have a schematic of the DFPlayer Mini with its components on it?

How do they decode mp3s?

I would like to modify the PCB or create something similar, but I cannot find how they are decoding mp3s and from what I have been looking at any IC to decode MP3's seems to be far more expensive than the DFPlayer to begin with.

If I wanted to design a sound player shield that read from an SD card not on board, where / what should I be looking for?

I am super happy with the quality of sound coming from the DFPlayer Mini and even its interface other than the SD card is inaccessible.

Thank you for your help.

2

The chip on the DF Miniplayer does the decoding, under license from the MP3 folks.

https://www.aliexpress.com/item/32860342792.html?src=google&albslr=221442105&src=google&albch=shopping&acnt=494-037-6276&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&&albagn=888888&albcp=2069223045&albag=83200626464&trgt=743612850714&crea=en32860342792&netw=u&device=c&gclid=EAIaIQobChMI89Czqtf74wIVGODICh2v-QAbEAQYAyABEgLi8fD_BwE&gclsrc=aw.ds

I can't see how they make money selling these for $0.98 each, shipping for $0.13, less than the price of sending a postcard.

3

under license from the MP3 folks.

The MP3 patents expired in 2017 so they no longer have to a pay royalties.