SDL support for floating point audio

[joncampbell123]

Describe the bug

Apparently recent versions of SDL2 and SDL3 are only able to provide floating point audio (something to do with Pipewire?).

If you ask for 16-bit PCM, it will still return float. Previous versions of DOSBox-X don't check if it changed.

Fortunately the mixer callback in DOSBox-X is a simple function and could be copies to make a 32-bit float version easily enough.

Steps to reproduce the behaviour

Run DOSBox-X in an environment that doesn't provide 16-bit PCM, observe loud distorted noise.

Expected behavior

No response

What operating system(s) this bug have occurred on?

Linux, with Pipewire

What version(s) of DOSBox-X have this bug?

All previous and current versions.

Used configuration

Output log

Additional information

No response

Have you checked that no similar bug report(s) exist?

• I have searched and didn't find any similar bug report.

Code of Conduct & Contributing Guidelines

• I agree to follow the code of conduct and the contributing guidelines.

[joncampbell123]

While we're at it, the mixer code should probably also validate that SDL chose the number of channels requested (stereo) as well.

[Jookia]

SDL will automatically convert your requested audio to the host's audio, so you can ask for any rate/frequency/format and it will do the conversion. But you can also ask it to give you a rate/frequency/format and it will give you the best option available within your constraints. As of 75aa320 the DOSBox-X code requests 16-bit PCM with any frequency/sample rate and gets back a stream that's converted by SDL to 32-bit float internally.

DOSBox-X was previously asking for ANY format, not just 16-bit PCM. So it got float instead.