def _build_network(
self,
input_specs: tf.keras.layers.InputSpec,
state_specs: Optional[Mapping[str, tf.keras.layers.InputSpec]] = None,
) -> Tuple[TensorMap, Union[TensorMap, Tuple[TensorMap, TensorMap]]]:
"""Builds the model network.
Args:
input_specs: the model input spec to use.
state_specs: a dict mapping a state name to the corresponding state spec.
State names should match with the `state` input/output dict.
Returns:
Inputs and outputs as a tuple. Inputs are expected to be a dict with
base input and states. Outputs are expected to be a dict of endpoints
and (optional) output states.
"""
state_specs = state_specs if state_specs is not None else {}
image_input = tf.keras.Input(shape=input_specs.shape[1:],
name='inputs')
states = {
name: tf.keras.Input(shape=spec.shape[1:],
dtype=spec.dtype,
name=name)
for name, spec in state_specs.items()
}
inputs = {**states, 'image': image_input}
endpoints = {}
x = image_input
num_layers = sum(
len(block.expand_filters) for block in self._block_specs
if isinstance(block, MovinetBlockSpec))
stochastic_depth_idx = 1
for block_idx, block in enumerate(self._block_specs):
if isinstance(block, StemSpec):
layer_obj = movinet_layers.Stem(
block.filters,
block.kernel_size,
block.strides,
conv_type=self._conv_type,
causal=self._causal,
activation=self._activation,
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
batch_norm_layer=self._norm,
batch_norm_momentum=self._norm_momentum,
batch_norm_epsilon=self._norm_epsilon,
state_prefix='state_stem',
name='stem')
x, states = layer_obj(x, states=states)
endpoints['stem'] = x
elif isinstance(block, MovinetBlockSpec):
if not (len(block.expand_filters) == len(block.kernel_sizes) ==
len(block.strides)):
raise ValueError(
'Lengths of block parameters differ: {}, {}, {}'.
format(len(block.expand_filters),
len(block.kernel_sizes), len(block.strides)))
params = list(
zip(block.expand_filters, block.kernel_sizes,
block.strides))
for layer_idx, layer in enumerate(params):
stochastic_depth_drop_rate = (
self._stochastic_depth_drop_rate *
stochastic_depth_idx / num_layers)
expand_filters, kernel_size, strides = layer
name = f'block{block_idx-1}_layer{layer_idx}'
layer_obj = movinet_layers.MovinetBlock(
block.base_filters,
expand_filters,
kernel_size=kernel_size,
strides=strides,
causal=self._causal,
activation=self._activation,
gating_activation=self._gating_activation,
stochastic_depth_drop_rate=stochastic_depth_drop_rate,
conv_type=self._conv_type,
se_type=self._se_type,
use_positional_encoding=self._use_positional_encoding
and self._causal,
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
batch_norm_layer=self._norm,
batch_norm_momentum=self._norm_momentum,
batch_norm_epsilon=self._norm_epsilon,
state_prefix=f'state_{name}',
name=name)
x, states = layer_obj(x, states=states)
endpoints[name] = x
stochastic_depth_idx += 1
elif isinstance(block, HeadSpec):
layer_obj = movinet_layers.Head(
project_filters=block.project_filters,
conv_type=self._conv_type,
activation=self._activation,
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
batch_norm_layer=self._norm,
batch_norm_momentum=self._norm_momentum,
batch_norm_epsilon=self._norm_epsilon,
state_prefix='state_head',
name='head')
x, states = layer_obj(x, states=states)
endpoints['head'] = x
else:
raise ValueError('Unknown block type {}'.format(block))
outputs = (endpoints, states) if self._output_states else endpoints
return inputs, outputs
def __init__(self,
model_id: str = 'a0',
causal: bool = False,
use_positional_encoding: bool = False,
conv_type: str = '3d',
input_specs: Optional[tf.keras.layers.InputSpec] = None,
activation: str = 'swish',
use_sync_bn: bool = True,
norm_momentum: float = 0.99,
norm_epsilon: float = 0.001,
kernel_initializer: str = 'HeNormal',
kernel_regularizer: Optional[str] = None,
bias_regularizer: Optional[str] = None,
stochastic_depth_drop_rate: float = 0.,
**kwargs):
"""MoViNet initialization function.
Args:
model_id: name of MoViNet backbone model.
causal: use causal mode, with CausalConv and CausalSE operations.
use_positional_encoding: if True, adds a positional encoding before
temporal convolutions and the cumulative global average pooling
layers.
conv_type: '3d', '2plus1d', or '3d_2plus1d'. '3d' configures the network
to use the default 3D convolution. '2plus1d' uses (2+1)D convolution
with Conv2D operations and 2D reshaping (e.g., a 5x3x3 kernel becomes
3x3 followed by 5x1 conv). '3d_2plus1d' uses (2+1)D convolution with
Conv3D and no 2D reshaping (e.g., a 5x3x3 kernel becomes 1x3x3 followed
by 5x1x1 conv).
input_specs: the model input spec to use.
activation: name of the activation function.
use_sync_bn: if True, use synchronized batch normalization.
norm_momentum: normalization momentum for the moving average.
norm_epsilon: small float added to variance to avoid dividing by
zero.
kernel_initializer: kernel_initializer for convolutional layers.
kernel_regularizer: tf.keras.regularizers.Regularizer object for Conv2D.
Defaults to None.
bias_regularizer: tf.keras.regularizers.Regularizer object for Conv2d.
Defaults to None.
stochastic_depth_drop_rate: the base rate for stochastic depth.
**kwargs: keyword arguments to be passed.
"""
block_specs = BLOCK_SPECS[model_id]
if input_specs is None:
input_specs = tf.keras.layers.InputSpec(shape=[None, None, None, None, 3])
if conv_type not in ('3d', '2plus1d', '3d_2plus1d'):
raise ValueError('Unknown conv type: {}'.format(conv_type))
self._model_id = model_id
self._block_specs = block_specs
self._causal = causal
self._use_positional_encoding = use_positional_encoding
self._conv_type = conv_type
self._input_specs = input_specs
self._use_sync_bn = use_sync_bn
self._activation = activation
self._norm_momentum = norm_momentum
self._norm_epsilon = norm_epsilon
if use_sync_bn:
self._norm = tf.keras.layers.experimental.SyncBatchNormalization
else:
self._norm = tf.keras.layers.BatchNormalization
self._kernel_initializer = kernel_initializer
self._kernel_regularizer = kernel_regularizer
self._bias_regularizer = bias_regularizer
self._stochastic_depth_drop_rate = stochastic_depth_drop_rate
if not isinstance(block_specs[0], StemSpec):
raise ValueError(
'Expected first spec to be StemSpec, got {}'.format(block_specs[0]))
if not isinstance(block_specs[-1], HeadSpec):
raise ValueError(
'Expected final spec to be HeadSpec, got {}'.format(block_specs[-1]))
self._head_filters = block_specs[-1].head_filters
if tf.keras.backend.image_data_format() == 'channels_last':
bn_axis = -1
else:
bn_axis = 1
# Build MoViNet backbone.
inputs = tf.keras.Input(shape=input_specs.shape[1:], name='inputs')
x = inputs
states = {}
endpoints = {}
num_layers = sum(len(block.expand_filters) for block in block_specs
if isinstance(block, MovinetBlockSpec))
stochastic_depth_idx = 1
for block_idx, block in enumerate(block_specs):
if isinstance(block, StemSpec):
x, states = movinet_layers.Stem(
block.filters,
block.kernel_size,
block.strides,
conv_type=self._conv_type,
causal=self._causal,
activation=self._activation,
kernel_initializer=kernel_initializer,
kernel_regularizer=kernel_regularizer,
batch_norm_layer=self._norm,
batch_norm_momentum=self._norm_momentum,
batch_norm_epsilon=self._norm_epsilon,
name='stem')(x, states=states)
endpoints['stem'] = x
elif isinstance(block, MovinetBlockSpec):
if not (len(block.expand_filters) == len(block.kernel_sizes) ==
len(block.strides)):
raise ValueError(
'Lenths of block parameters differ: {}, {}, {}'.format(
len(block.expand_filters),
len(block.kernel_sizes),
len(block.strides)))
params = list(zip(block.expand_filters,
block.kernel_sizes,
block.strides))
for layer_idx, layer in enumerate(params):
stochastic_depth_drop_rate = (
self._stochastic_depth_drop_rate * stochastic_depth_idx /
num_layers)
expand_filters, kernel_size, strides = layer
name = f'b{block_idx-1}/l{layer_idx}'
x, states = movinet_layers.MovinetBlock(
block.base_filters,
expand_filters,
kernel_size=kernel_size,
strides=strides,
causal=self._causal,
activation=self._activation,
stochastic_depth_drop_rate=stochastic_depth_drop_rate,
conv_type=self._conv_type,
use_positional_encoding=
self._use_positional_encoding and self._causal,
kernel_initializer=kernel_initializer,
kernel_regularizer=kernel_regularizer,
batch_norm_layer=self._norm,
batch_norm_momentum=self._norm_momentum,
batch_norm_epsilon=self._norm_epsilon,
name=name)(x, states=states)
endpoints[name] = x
stochastic_depth_idx += 1
elif isinstance(block, HeadSpec):
x, states = movinet_layers.Head(
project_filters=block.project_filters,
conv_type=self._conv_type,
activation=self._activation,
kernel_initializer=kernel_initializer,
kernel_regularizer=kernel_regularizer,
batch_norm_layer=self._norm,
batch_norm_momentum=self._norm_momentum,
batch_norm_epsilon=self._norm_epsilon)(x, states=states)
endpoints['head'] = x
else:
raise ValueError('Unknown block type {}'.format(block))
self._output_specs = {l: endpoints[l].get_shape() for l in endpoints}
inputs = {
'image': inputs,
'states': {
name: tf.keras.Input(shape=state.shape[1:], name=f'states/{name}')
for name, state in states.items()
},
}
outputs = (endpoints, states)
super(Movinet, self).__init__(inputs=inputs, outputs=outputs, **kwargs)