Raspberry Pi Pico compilation error in mp3d_scale_pcm

[MrJake222]

Error: selected processor does not support ssat r0,#16,r0 in Thumb mode.

How much slower is the no-assembler version? Is this a real issue?

[akeamc]

I'm trying to compile the Rust bindings (viriw/rmp3) for my RP2040, but am facing the same issue as you. Did you find a solution?

[MrJake222]

I've abandoned this library as it's not feasible to decode MP3 on such a small processor (no floating point math).

BUT I've managed to get mp3 to decode using HelixMP3. Here is a link to my fork where I've already implemented some extension to it: namely the default implementation and cmake support. Feel free to take a look.

[akeamc]

Thanks for the speedy reply, to a thread this old! I'll give HelixMP3 a shot.

[RocksoC-Prime]

This PR from 2022 addresses the issue.

I'm using the same library as @akeamc, and I can confirm that after manually patching out the inline assembly it works as intended, albeit too slowly to practically use on the RP2040, at least with my relatively naïve approach.

I suppose it's kind of silly to ask for a patch to support a µC that for most intents and purposes isn't fast enough to use this library, but eh. Considering it's just an extra check at build-time why not.

[MrJake222]

Helixmp3 can decode full 320kbps mp3 files without issues on rp2040. I've built a whole radio around it. https://mrwski.eu/projects/#picoradio