def frame(signal, frame_length, frame_step, pad_end=False, pad_value=0, axis=-1,
name=None):
"""Expands `signal`'s `axis` dimension into frames of `frame_length`.
Slides a window of size `frame_length` over `signal`s `axis` dimension
with a stride of `frame_step`, replacing the `axis` dimension with
`[frames, frame_length]` frames.
If `pad_end` is True, window positions that are past the end of the `axis`
dimension are padded with `pad_value` until the window moves fully past the
end of the dimension. Otherwise, only window positions that fully overlap the
`axis` dimension are produced.
For example:
```python
pcm = tf.placeholder(tf.float32, [None, 9152])
frames = tf.contrib.signal.frame(pcm, 512, 180)
magspec = tf.abs(tf.spectral.rfft(frames, [512]))
image = tf.expand_dims(magspec, 3)
```
Args:
signal: A `[..., samples, ...]` `Tensor`. The rank and dimensions
may be unknown. Rank must be at least 1.
frame_length: The frame length in samples. An integer or scalar `Tensor`.
frame_step: The frame hop size in samples. An integer or scalar `Tensor`.
pad_end: Whether to pad the end of `signal` with `pad_value`.
pad_value: An optional scalar `Tensor` to use where the input signal
does not exist when `pad_end` is True.
axis: A scalar integer `Tensor` indicating the axis to frame. Defaults to
the last axis. Supports negative values for indexing from the end.
name: An optional name for the operation.
Returns:
A `Tensor` of frames with shape `[..., frames, frame_length, ...]`.
Raises:
ValueError: If `frame_length`, `frame_step`, or `pad_value` are not scalar.
"""
with ops.name_scope(name, "frame", [signal, frame_length, frame_step,
pad_value]):
signal = ops.convert_to_tensor(signal, name="signal")
frame_length = ops.convert_to_tensor(frame_length, name="frame_length")
frame_step = ops.convert_to_tensor(frame_step, name="frame_step")
axis = ops.convert_to_tensor(axis, name="axis")
signal.shape.with_rank_at_least(1)
frame_length.shape.assert_has_rank(0)
frame_step.shape.assert_has_rank(0)
axis.shape.assert_has_rank(0)
result_shape = _infer_frame_shape(signal, frame_length, frame_step, pad_end,
axis)
# Axis can be negative. Convert it to positive.
signal_rank = array_ops.rank(signal)
axis = math_ops.range(signal_rank)[axis]
signal_shape = array_ops.shape(signal)
outer_dimensions, length_samples, inner_dimensions = array_ops.split(
signal_shape, [axis, 1, signal_rank - 1 - axis])
length_samples = array_ops.reshape(length_samples, [])
num_outer_dimensions = array_ops.size(outer_dimensions)
num_inner_dimensions = array_ops.size(inner_dimensions)
# If padding is requested, pad the input signal tensor with pad_value.
if pad_end:
pad_value = ops.convert_to_tensor(pad_value, signal.dtype)
pad_value.shape.assert_has_rank(0)
# Calculate number of frames, using double negatives to round up.
num_frames = -(-length_samples // frame_step)
# Pad the signal by up to frame_length samples based on how many samples
# are remaining starting from last_frame_position.
pad_samples = math_ops.maximum(
0, frame_length + frame_step * (num_frames - 1) - length_samples)
# Pad the inner dimension of signal by pad_samples.
paddings = array_ops.concat(
[array_ops.zeros([num_outer_dimensions, 2], dtype=pad_samples.dtype),
[[0, pad_samples]],
array_ops.zeros([num_inner_dimensions, 2], dtype=pad_samples.dtype)],
0)
signal = array_ops.pad(signal, paddings, constant_values=pad_value)
signal_shape = array_ops.shape(signal)
length_samples = signal_shape[axis]
else:
num_frames = math_ops.maximum(
0, 1 + (length_samples - frame_length) // frame_step)
subframe_length = util_ops.gcd(frame_length, frame_step)
subframes_per_frame = frame_length // subframe_length
subframes_per_hop = frame_step // subframe_length
num_subframes = length_samples // subframe_length
slice_shape = array_ops.concat([outer_dimensions,
[num_subframes * subframe_length],
inner_dimensions], 0)
subframe_shape = array_ops.concat([outer_dimensions,
[num_subframes, subframe_length],
inner_dimensions], 0)
subframes = array_ops.reshape(array_ops.strided_slice(
signal, array_ops.zeros_like(signal_shape),
slice_shape), subframe_shape)
# frame_selector is a [num_frames, subframes_per_frame] tensor
# that indexes into the appropriate frame in subframes. For example:
# [[0, 0, 0, 0], [2, 2, 2, 2], [4, 4, 4, 4]]
frame_selector = array_ops.reshape(
math_ops.range(num_frames) * subframes_per_hop, [num_frames, 1])
# subframe_selector is a [num_frames, subframes_per_frame] tensor
# that indexes into the appropriate subframe within a frame. For example:
# [[0, 1, 2, 3], [0, 1, 2, 3], [0, 1, 2, 3]]
subframe_selector = array_ops.reshape(
math_ops.range(subframes_per_frame), [1, subframes_per_frame])
# Adding the 2 selector tensors together produces a [num_frames,
# subframes_per_frame] tensor of indices to use with tf.gather to select
# subframes from subframes. We then reshape the inner-most
# subframes_per_frame dimension to stitch the subframes together into
# frames. For example: [[0, 1, 2, 3], [2, 3, 4, 5], [4, 5, 6, 7]].
selector = frame_selector + subframe_selector
frames = array_ops.reshape(
array_ops.gather(subframes, selector, axis=axis),
array_ops.concat([outer_dimensions, [num_frames, frame_length],
inner_dimensions], 0))
if result_shape:
frames.set_shape(result_shape)
return frames
def overlap_and_add(signal, frame_step, name=None):
"""Reconstructs a signal from a framed representation.
Adds potentially overlapping frames of a signal with shape
`[..., frames, frame_length]`, offsetting subsequent frames by `frame_step`.
The resulting tensor has shape `[..., output_size]` where
output_size = (frames - 1) * frame_step + frame_length
Args:
signal: A [..., frames, frame_length] `Tensor`. All dimensions may be
unknown, and rank must be at least 2.
frame_step: An integer or scalar `Tensor` denoting overlap offsets. Must be
less than or equal to `frame_length`.
name: An optional name for the operation.
Returns:
A `Tensor` with shape `[..., output_size]` containing the overlap-added
frames of `signal`'s inner-most two dimensions.
Raises:
ValueError: If `signal`'s rank is less than 2, `frame_step` is not a scalar
integer or `frame_step` is greater than `frame_length`.
"""
with ops.name_scope(name, "overlap_and_add", [signal, frame_step]):
signal = ops.convert_to_tensor(signal, name="signal")
signal.shape.with_rank_at_least(2)
frame_step = ops.convert_to_tensor(frame_step, name="frame_step")
frame_step.shape.assert_has_rank(0)
if not frame_step.dtype.is_integer:
raise ValueError("frame_step must be an integer. Got %s" %
frame_step.dtype)
signal_shape = array_ops.shape(signal)
# All dimensions that are not part of the overlap-and-add. Can be empty for
# rank 2 inputs.
outer_dimensions = signal_shape[:-2]
# If frame_length and frame_step are known at graph construction time, check
# frame_step is less than or equal to frame_length.
frame_step_static = tensor_util.constant_value(frame_step)
if (frame_step_static is not None and signal.shape.ndims is not None and
signal.shape.dims[-1].value is not None):
if frame_step_static > signal.shape.dims[-1].value:
raise ValueError(
"frame_step (%d) must be less than or equal to "
"frame_length (%d)" % (
frame_step_static, signal.shape.dims[-1].value))
# If frame_length is equal to frame_step, there's no overlap so just
# reshape the tensor.
if frame_step_static == signal.shape.dims[-1].value:
return array_ops.reshape(signal, array_ops.concat(
[outer_dimensions, [-1]], 0))
signal_rank = array_ops.rank(signal)
frames = signal_shape[-2]
frame_length = signal_shape[-1]
subframe_length = util_ops.gcd(frame_length, frame_step)
subframe_step = frame_step // subframe_length
subframes_per_frame = frame_length // subframe_length
output_size = frame_step * (frames - 1) + frame_length
output_subframes = output_size // subframe_length
# To avoid overlap-adding sample-by-sample, we overlap-add at the "subframe"
# level, where a subframe is gcd(frame_length, frame_step). Reshape signal
# from [..., frames, frame_length] into [..., subframes, subframe_length].
subframe_shape = array_ops.concat(
[outer_dimensions, [-1, subframe_length]], 0)
subframe_signal = array_ops.reshape(signal, subframe_shape)
# Now we shuffle the last [subframes, subframe_length] dimensions to the
# front.
# TODO(rjryan): Add an axis argument to unsorted_segment_sum so we can
# avoid this pair of transposes.
subframe_signal = _shuffle_to_front(subframe_signal, 2)
# Use unsorted_segment_sum to add overlapping subframes together.
segment_ids = array_ops.reshape(shape_ops.frame(
math_ops.range(output_subframes), subframes_per_frame, subframe_step,
pad_end=False), [-1])
result = math_ops.unsorted_segment_sum(subframe_signal, segment_ids,
num_segments=output_subframes)
# result is a [subframes, subframe_length, ...outer_dimensions] tensor. We
# return a [...outer_dimensions, output_size] tensor with a transpose and
# reshape.
result_shape = array_ops.concat([outer_dimensions, [output_size]], 0)
return array_ops.reshape(_shuffle_to_front(result, signal_rank - 2),
result_shape)
def frame(signal, frame_length, frame_step, pad_end=False, pad_value=0, axis=-1,
name=None):
"""Expands `signal`'s `axis` dimension into frames of `frame_length`.
Slides a window of size `frame_length` over `signal`'s `axis` dimension
with a stride of `frame_step`, replacing the `axis` dimension with
`[frames, frame_length]` frames.
If `pad_end` is True, window positions that are past the end of the `axis`
dimension are padded with `pad_value` until the window moves fully past the
end of the dimension. Otherwise, only window positions that fully overlap the
`axis` dimension are produced.
For example:
```python
pcm = tf.placeholder(tf.float32, [None, 9152])
frames = tf.contrib.signal.frame(pcm, 512, 180)
magspec = tf.abs(tf.spectral.rfft(frames, [512]))
image = tf.expand_dims(magspec, 3)
```
Args:
signal: A `[..., samples, ...]` `Tensor`. The rank and dimensions
may be unknown. Rank must be at least 1.
frame_length: The frame length in samples. An integer or scalar `Tensor`.
frame_step: The frame hop size in samples. An integer or scalar `Tensor`.
pad_end: Whether to pad the end of `signal` with `pad_value`.
pad_value: An optional scalar `Tensor` to use where the input signal
does not exist when `pad_end` is True.
axis: A scalar integer `Tensor` indicating the axis to frame. Defaults to
the last axis. Supports negative values for indexing from the end.
name: An optional name for the operation.
Returns:
A `Tensor` of frames with shape `[..., frames, frame_length, ...]`.
Raises:
ValueError: If `frame_length`, `frame_step`, `pad_value`, or `axis` are not
scalar.
"""
with ops.name_scope(name, "frame", [signal, frame_length, frame_step,
pad_value]):
signal = ops.convert_to_tensor(signal, name="signal")
frame_length = ops.convert_to_tensor(frame_length, name="frame_length")
frame_step = ops.convert_to_tensor(frame_step, name="frame_step")
axis = ops.convert_to_tensor(axis, name="axis")
signal.shape.with_rank_at_least(1)
frame_length.shape.assert_has_rank(0)
frame_step.shape.assert_has_rank(0)
axis.shape.assert_has_rank(0)
result_shape = _infer_frame_shape(signal, frame_length, frame_step, pad_end,
axis)
# Axis can be negative. Convert it to positive.
signal_rank = array_ops.rank(signal)
axis = math_ops.range(signal_rank)[axis]
signal_shape = array_ops.shape(signal)
outer_dimensions, length_samples, inner_dimensions = array_ops.split(
signal_shape, [axis, 1, signal_rank - 1 - axis])
length_samples = array_ops.reshape(length_samples, [])
num_outer_dimensions = array_ops.size(outer_dimensions)
num_inner_dimensions = array_ops.size(inner_dimensions)
# If padding is requested, pad the input signal tensor with pad_value.
if pad_end:
pad_value = ops.convert_to_tensor(pad_value, signal.dtype)
pad_value.shape.assert_has_rank(0)
# Calculate number of frames, using double negatives to round up.
num_frames = -(-length_samples // frame_step)
# Pad the signal by up to frame_length samples based on how many samples
# are remaining starting from last_frame_position.
pad_samples = math_ops.maximum(
0, frame_length + frame_step * (num_frames - 1) - length_samples)
# Pad the inner dimension of signal by pad_samples.
paddings = array_ops.concat(
[array_ops.zeros([num_outer_dimensions, 2], dtype=pad_samples.dtype),
[[0, pad_samples]],
array_ops.zeros([num_inner_dimensions, 2], dtype=pad_samples.dtype)],
0)
signal = array_ops.pad(signal, paddings, constant_values=pad_value)
signal_shape = array_ops.shape(signal)
length_samples = signal_shape[axis]
else:
num_frames = math_ops.maximum(
0, 1 + (length_samples - frame_length) // frame_step)
subframe_length = util_ops.gcd(frame_length, frame_step)
subframes_per_frame = frame_length // subframe_length
subframes_per_hop = frame_step // subframe_length
num_subframes = length_samples // subframe_length
slice_shape = array_ops.concat([outer_dimensions,
[num_subframes * subframe_length],
inner_dimensions], 0)
subframe_shape = array_ops.concat([outer_dimensions,
[num_subframes, subframe_length],
inner_dimensions], 0)
subframes = array_ops.reshape(array_ops.strided_slice(
signal, array_ops.zeros_like(signal_shape),
slice_shape), subframe_shape)
# frame_selector is a [num_frames, subframes_per_frame] tensor
# that indexes into the appropriate frame in subframes. For example:
# [[0, 0, 0, 0], [2, 2, 2, 2], [4, 4, 4, 4]]
frame_selector = array_ops.reshape(
math_ops.range(num_frames) * subframes_per_hop, [num_frames, 1])
# subframe_selector is a [num_frames, subframes_per_frame] tensor
# that indexes into the appropriate subframe within a frame. For example:
# [[0, 1, 2, 3], [0, 1, 2, 3], [0, 1, 2, 3]]
subframe_selector = array_ops.reshape(
math_ops.range(subframes_per_frame), [1, subframes_per_frame])
# Adding the 2 selector tensors together produces a [num_frames,
# subframes_per_frame] tensor of indices to use with tf.gather to select
# subframes from subframes. We then reshape the inner-most
# subframes_per_frame dimension to stitch the subframes together into
# frames. For example: [[0, 1, 2, 3], [2, 3, 4, 5], [4, 5, 6, 7]].
selector = frame_selector + subframe_selector
frames = array_ops.reshape(
array_ops.gather(subframes, selector, axis=axis),
array_ops.concat([outer_dimensions, [num_frames, frame_length],
inner_dimensions], 0))
if result_shape:
frames.set_shape(result_shape)
return frames