Problem when setting buffer time (alsa backend) #391
Description
Continuing from #247, I'm still getting the problem (the story is I removed the set_buffer call but it was re-introduced as it created unacceptable latency). I've implemented dumping the HwParams (code below) and to be honest it looks like a bug in the ALSA driver for my sound card. I have an idea to make it work on my setup - that is to try to set the buffer time, and just to leave it unconstrained if there is an error setting it. I'll knock up a PR with the idea in it.
Code to implement `Debug` for `HwParams`
impl fmt::Debug for HwParams {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
unsafe {
match dump_alsa(|outputp| alsa::snd_pcm_hw_params_dump(self.0, outputp) == 0) {
Some(msg) => write!(f, "HwParams({})", msg),
None => f.write_str("HwParams")
}
}
}
}
/// output of dump_fn should be whether the function ran successfully (false means an error)
unsafe fn dump_alsa(dump_fn: impl FnOnce(*mut alsa::snd_output_t) -> bool) -> Option<String> {
let mut outputp: *mut alsa::snd_output_t = ptr::null_mut();
if let Err(e) = check_errors(alsa::snd_output_buffer_open(&mut outputp)) {
return None;
}
if ! dump_fn(outputp) {
return None;
}
let mut output_cstr: *mut libc::c_char = ptr::null_mut();
let len = alsa::snd_output_buffer_string(outputp, &mut output_cstr);
// be careful to drop this before any mutating calls to outputp
let output_cstr: &[u8] = std::slice::from_raw_parts(output_cstr as *const u8, len);
Some(String::from_utf8_lossy(output_cstr).into_owned())
}