Struct MultiTrackComposer 

pub struct MultiTrackComposer { /* private fields */ }

Composes multiple video layers onto a solid-colour canvas.

Layers are composited in the order they are added (first at the bottom). The resulting FilterGraph is source-only — call FilterGraph::pull_video in a loop to extract the output frames. The graph terminates when the last (top) layer finishes.

Examples

use ff_filter::{AnimatedValue, LayerSource, MultiTrackComposer, VideoLayer};

let mut graph = MultiTrackComposer::new(1920, 1080)
    .add_layer(VideoLayer {
        source: LayerSource::File("clip.mp4".into()),
        proxy: None,
        x: AnimatedValue::Static(0.0),
        y: AnimatedValue::Static(0.0),
        scale_x: AnimatedValue::Static(1.0),
        scale_y: AnimatedValue::Static(1.0),
        rotation: AnimatedValue::Static(0.0),
        opacity: AnimatedValue::Static(1.0),
        blend_mode: BlendMode::Normal,
        composite_op: CompositeOp::Over,
        effects: vec![],
    })
    .build()?;

while let Some(frame) = graph.pull_video()? {
    // encode or display `frame`
}

Implementations

impl MultiTrackComposer

pub fn new(canvas_width: u32, canvas_height: u32) -> Self

Creates a new composer with a black canvas and no layers.

pub fn background(self, rgb: Rgb) -> Self

Sets the canvas background colour and returns the updated composer.

pub fn frame_rate(self, fps: f64) -> Self

Sets the output frame rate (frames per second) of the composition.

The background canvas and the per-layer fps conform are generated at this rate, so it MUST match the rate the caller encodes/muxes at — otherwise the composited video is stretched or compressed by this_rate / encode_rate while the audio stays correct, desyncing A/V. Defaults to 30.0.

pub fn add_layer(self, layer: VideoLayer) -> Self

Appends a video layer and returns the updated composer.

A layer that cross-fades from its predecessor carries a FilterStep::XFade in its effects; the compositor wires the transition’s second input from the preceding layer at build time.

pub fn build(self) -> Result<FilterGraph, FilterError>

Builds a source-only FilterGraph that composites all layers.

Errors

• FilterError::CompositionFailed — canvas width or height is zero, no layers were added, or an underlying FFmpeg graph-construction call failed.