Running through headphones causing out of sync frames

[petar-dambovaliev]

Hi, i am making an application that would allow people to compose music via a script.
I am in early development stage and i am having some issues.
When i increase and decrease the song tempo, all instruments slow down and speed up in sync.
However, when i plug in my headphones and i change the tempo, all instruments go out of sync.
I have debugged the way i calculate note duration and seems to be correct.
So i don't know what else to do but post my problem here.

const SEC_PER_MIN: f32 = 60.0;

pub struct Rates<'a> {
    pub(crate) sample_rate: Hz,
    pub(crate) beat_per_min: f32,
    pub(crate) duration: &'a Duration,
}

pub fn calc_duration(rates: Rates) -> Hz {
    // example rate per beat =  (44100 samples per second * 60) / 60 beats per minute
    let rate_per_beat: f32 = (rates.sample_rate * SEC_PER_MIN) / rates.beat_per_min;
    rate_per_beat * rates.duration.to_beats()
}

#[derive(Debug, Clone)]
pub enum Duration {
    Whole,
    HalfDotted,
    Half,
    QuarterDotted,
    Quarter,
    EightDotted,
    Eight,
    SixteenthDotted,
    Sixteenth,
    ThirtySecondDotted,
    ThirtySecond,
}

impl Duration {
    pub fn to_beats(&self) -> f32 {
        match self {
            Self::Whole => 4.0,
            Self::HalfDotted => 3.0,
            Self::Half => 2.0,
            Self::QuarterDotted => 1.5,
            Self::Quarter => 1.0,
            Self::EightDotted => 0.75,
            Self::Eight => 0.5,
            Self::SixteenthDotted => 0.375,
            Self::Sixteenth => 0.25,
            Self::ThirtySecondDotted => 0.1875,
            Self::ThirtySecond => 0.125,
        }
    }
}

[LastExceed]

Streams are semantically independent of each other, even if they are on the same device. They have no obligation to stay synchronized. I recommend mixing all your instruments together yourself, and piping the result into a single output stream, so you're in control of synchronization.