FiLM API

class FiLM

Feature-wise Linear Modulation (FiLM)

Given an input (input_dim x num_frames) and a condition (condition_dim x num_frames), compute: scale, shift = Conv1x1(condition) split across channels (top/bottom half, respectively) output = input * scale + shift (elementwise)

FiLM applies per-channel scaling and optional shifting based on conditioning input, allowing the model to adapt its behavior based on external signals.

Public Functions

inline FiLM(const int condition_dim, const int input_dim, const bool shift, const int groups = 1)

Constructor.

Parameters:

• condition_dim – Size of the conditioning input

• input_dim – Size of the input to be modulated

• shift – Whether to apply both scale and shift (true) or only scale (false)

• groups – Number of groups for grouped convolution in the condition-to-scale-shift submodule (default: 1)

inline Eigen::MatrixXf &GetOutput()

Get the entire internal output buffer.

This is intended for internal wiring between layers; callers should treat the buffer as pre-allocated storage and only consider the first num_frames columns valid for a given processing call. Slice with .leftCols(num_frames) as needed.

Returns:

Reference to the output buffer

inline const Eigen::MatrixXf &GetOutput() const

Get the entire internal output buffer (const version)

Returns:

Const reference to the output buffer

inline void SetMaxBufferSize(const int maxBufferSize)

Resize buffers to handle maxBufferSize frames.

Parameters:

maxBufferSize – Maximum number of frames to process in a single call

inline void set_weights_(std::vector<float>::iterator &weights)

Set the parameters (weights) of this module.

Parameters:

weights – Iterator to the weights vector. Will be advanced as weights are consumed.

inline long get_condition_dim() const

Get the condition dimension.

Returns:

Size of the conditioning input

inline long get_input_dim() const

Get the input dimension.

Returns:

Size of the input to be modulated

inline void Process(const Eigen::Ref<const Eigen::MatrixXf> &input, const Eigen::Ref<const Eigen::MatrixXf> &condition, const int num_frames)

Process input with conditioning.

Writes (input_dim x num_frames) into internal output buffer; access via GetOutput(). Uses Eigen::Ref to accept matrices and block expressions without creating temporaries (real-time safe).

Parameters:

• input – Input matrix (input_dim x num_frames)

• condition – Conditioning matrix (condition_dim x num_frames)

• num_frames – Number of frames to process

inline void Process_(Eigen::Ref<Eigen::MatrixXf> input, const Eigen::Ref<const Eigen::MatrixXf> &condition, const int num_frames)

Process input with conditioning (in-place)

Uses Eigen::Ref to accept matrices and block expressions without creating temporaries (real-time safe). Modifies the input matrix directly.

Parameters:

• input – Input matrix (input_dim x num_frames), will be modified in-place

• condition – Conditioning matrix (condition_dim x num_frames)

• num_frames – Number of frames to process