VioEstimator API

VioEstimator<T, Backend = MsckfBackend<T>> (sdk/include/branes/sdk/vio_estimator.hpp, #45) is the public façade the daemons drive. It owns the visual front end and the selected estimator backend, and exposes a small, lifecycle-gated API.

The API

void configure(const VioConfig&);              // fix parameters, init the backend
void activate();   void deactivate();          // managed lifecycle
void teardown();
void feed_imu(std::span<const ImuMeasurement<T>>);     // inputs by view
void feed_image(double t, cv::Image<const std::uint8_t>);
Pose      current_pose()  const;               // SE3 T_world_imu
NavState  current_state() const;
void      reset();

Inputs are non-owning views — an Image view for frames, a span for IMU batches; the estimator copies nothing it doesn’t need to retain.

Lifecycle — mirroring the Rust RM

The estimator’s states mirror the Resource Manager’s managed lifecycle (Resource Manager):

Unconfigured ──configure──▶ Inactive ──activate──▶ Active
                              ▲                       │
                              └────deactivate/reset───┘   teardown ─▶ (terminal)

Measurements are consumed only while Active — feed_imu/feed_image are no-ops otherwise. This honors the “no dynamic reconfiguration on the hot path” rule: parameters are fixed at configure, and configure is ignored while Active. To change them, deactivate() then configure() (which also clears runtime state) and activate() again. After teardown() the estimator is spent; construct a new one.

What feed_image does

It runs the front-end loop (pyramid → KLT-track existing features → re-detect FAST corners, suppressing near existing tracks → assign stable ids), producing one FrontendObservation per surviving track, and hands them to the backend’s process_camera. A telemetry accessor, num_tracked_features(), exposes the current track count.

Backend substitutability

Because Backend is a template parameter constrained only by the VioBackend interface, the estimator can be instantiated on MsckfBackend<T> (the default) or on the SlidingWindowBackend<T> skeleton — the front end and the public API are identical either way.

Validated

Tests cover the lifecycle gating (feeds ignored unless Active; correct transitions; reset/teardown) and a full front-end → backend run on translating synthetic frames that detects and persistently tracks features, keeps the covariance PSD and the clone window bounded, and produces a finite pose. The runnable EuRoC replay example lives in the dataset harness (#46).