Struct Transport 

pub struct Transport {

    pub tempo: Option<f64>,
    pub time_sig_numerator: Option<i32>,
    pub time_sig_denominator: Option<i32>,
    pub project_time_samples: Option<i64>,
    pub project_time_beats: Option<f64>,
    pub bar_position_beats: Option<f64>,
    pub cycle_start_beats: Option<f64>,
    pub cycle_end_beats: Option<f64>,
    pub is_playing: bool,
    pub is_recording: bool,
    pub is_cycle_active: bool,
    pub system_time_ns: Option<i64>,
    pub continuous_time_samples: Option<i64>,
    pub samples_to_next_clock: Option<i32>,
    pub smpte_offset_subframes: Option<i32>,
    pub frame_rate: Option<FrameRate>,
}

Host transport and timing information.

Contains tempo, time signature, playback position, and transport state. All timing fields are Option<T> because not all hosts provide all data. Playback state fields (is_playing, etc.) are always valid.

Field Availability

Different DAWs provide different subsets of transport information:

• Tempo/time signature: Most DAWs provide these
• Musical position: Common but not universal
• SMPTE/timecode: Only in video-oriented DAWs
• System time: Rarely provided

Always check Option fields before use and provide sensible fallbacks.

Example

// Safe tempo access with fallback
let tempo = context.transport.tempo.unwrap_or(120.0);

// Check if we have valid musical position
if let Some(beats) = context.transport.project_time_beats {
    // Sync effect to beat position
}

// Transport state is always valid
if context.transport.is_playing {
    // Process audio
} else {
    // Maybe bypass or fade out
}

Fields

tempo: Option<f64>

Current tempo in BPM (beats per minute).

Typically 20-300, but can be any positive value.

time_sig_numerator: Option<i32>

Time signature numerator (e.g., 4 in 4/4, 3 in 3/4, 6 in 6/8).

time_sig_denominator: Option<i32>

Time signature denominator (e.g., 4 in 4/4, 4 in 3/4, 8 in 6/8).

project_time_samples: Option<i64>

Project time in samples from the start of the timeline.

This is the primary sample-accurate position. Always increments during playback, may jump on loop or locate.

project_time_beats: Option<f64>

Project time in quarter notes (musical time).

Takes tempo changes into account. 1.0 = one quarter note.

bar_position_beats: Option<f64>

Position of the last bar start in quarter notes.

Useful for bar-synchronized effects (e.g., 4-bar delay).

cycle_start_beats: Option<f64>

Loop/cycle start position in quarter notes.

cycle_end_beats: Option<f64>

Loop/cycle end position in quarter notes.

is_playing: bool

True if transport is currently playing.

This is always valid (not an Option) because VST3 always provides it.

is_recording: bool

True if recording is active.

is_cycle_active: bool

True if loop/cycle mode is enabled.

system_time_ns: Option<i64>

System time in nanoseconds.

Can be used to sync to wall-clock time. Rarely provided by hosts.

continuous_time_samples: Option<i64>

Continuous time in samples (doesn’t reset on loop).

Unlike project_time_samples, this never jumps during cycle playback - it always increments monotonically.

samples_to_next_clock: Option<i32>

Samples until next MIDI beat clock (24 ppqn).

Used for generating MIDI clock messages or syncing to external gear.

smpte_offset_subframes: Option<i32>

SMPTE offset in subframes (1/80th of a frame).

For video synchronization. Divide by 80 to get frame offset.

frame_rate: Option<FrameRate>

SMPTE frame rate.

Implementations

impl Transport

pub fn time_signature(&self) -> Option<(i32, i32)>

Returns the time signature as a tuple (numerator, denominator).

Returns None if either component is unavailable.

Example

if let Some((num, denom)) = transport.time_signature() {
    println!("Playing in {}/{} time", num, denom);
}

pub fn cycle_range(&self) -> Option<(f64, f64)>

Returns the loop/cycle range in quarter notes as (start, end).

Returns None if either endpoint is unavailable.

Example

if let Some((start, end)) = transport.cycle_range() {
    let loop_length_beats = end - start;
}

pub fn is_looping(&self) -> bool

Returns true if loop is active and has valid range.

pub fn has_timing_info(&self) -> bool

Returns true if any timing info is available.

pub fn has_time_signature(&self) -> bool

Returns true if time signature info is complete.

pub fn smpte_frames(&self) -> Option<(i32, i32)>

Converts SMPTE subframes to (frames, subframes) tuple.

Subframes are 0-79 within each frame. Uses Euclidean division to correctly handle negative offsets.

Trait Implementations

impl Clone for Transport

fn clone(&self) -> Transport

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Transport

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Transport

fn default() -> Transport

Returns the “default value” for a type.

impl Copy for Transport