fix missing support for other sample formats than F32 in cpal output

[emuell]

fixes #2

[leofidus]

That was fast. This definitely feels like the correct way to handle it.

Testing it, it almost works. By which I mean it initially failed because device.default_output_config() in preferred_output_config returns an unsupported output config. As a test I changed the function like this for manually select a fallback

fn preferred_output_config(
        device: &cpal::Device,
    ) -> Result<cpal::SupportedStreamConfig, Error> {
        for s in device.supported_output_configs()? {
            dbg!(&s);
            let rates = s.min_sample_rate()..=s.max_sample_rate();
            if s.channels() == PREFERRED_CHANNELS
                && s.sample_format() == PREFERRED_SAMPLE_FORMAT
                && rates.contains(&PREFERRED_SAMPLE_RATE)
            {
                return Ok(s.with_sample_rate(PREFERRED_SAMPLE_RATE));
            }
        }

        let fallback_config =
            device
                .supported_output_configs()?
                .next()
                .ok_or(Error::OutputDeviceError(Box::new(
                    cpal::DefaultStreamConfigError::DeviceNotAvailable,
                )))?;
        let rates = fallback_config.min_sample_rate()..=fallback_config.max_sample_rate();
        if rates.contains(&PREFERRED_SAMPLE_RATE) {
            return Ok(fallback_config.with_sample_rate(PREFERRED_SAMPLE_RATE));
        }
        return Ok(fallback_config.with_sample_rate(fallback_config.max_sample_rate()));
    }

And now it works.

Which confirms that the handling of non-f32 sample formats now works. I will file an issue with cpal about what looks like a bug in default_output_config(), as that is really a separate though related issue. Not sure if you want to work around that bug or just wait for it to be fixed by cpal

[emuell]

Quicky looking at this, both supported_output_configs and default_output_config get the format from IAudioClient::GetMixFormat(), so both should result into a valid format. However, I can't replicate this on my machines, so I think it's better if you report this issue to the CPAL team.

We're currently using cpal 0.15, but according to https://github.com/RustAudio/cpal/blob/master/CHANGELOG.md this wasn't fixed there. I'll update to 0.16 anyway after merging this as there are other nice improvements.

Thanks for the feedback!