Convolve

class baseband.tasks.Convolve(ih, response, *, offset=0, samples_per_frame=None)[source] [edit on github]

Bases: baseband_tasks.convolution.ConvolveSamples

Convolve a time stream with a response, in the Fourier domain.

The convolution is done via multiplication in the Fourier domain, which is faster than direct convolution for all but very simple responses.

Parameters
ihtask or baseband stream reader

Input data stream, with time as the first axis.

responsendarray

Response to convolce the time stream with. If one-dimensional, assumed to apply to the sample axis of ih.

offsetint, optional

Where samples should be considered to be taken from. For the default of 0, a given sample has the same time as the convolution of the filter with all preceding samples.

samples_per_frameint, optional

Number of convolved samples which should be produced in one go. The number of input samples used will be larger to avoid wrapping. If not given, as produced by the larger of the input samples per frame minus padding or the minimum power of 2 of input samples that yields at least 75% efficiency.

See also

ConvolveSamples

convolution in the time domain (for simple responses)

baseband_tasks.fourier.fft_maker

to select the FFT package used.

Attributes Summary

closed

complex_data

dtype

Data type of the output.

meta

ndim

Number of dimensions of the output.

offset

sample_rate

Number of complete samples per second.

sample_shape

Shape of a complete sample.

samples_per_frame

Number of samples per frame of data.

shape

Shape of the output.

size

Number of component samples in the output.

start_time

Start time of the output.

stop_time

Time at the end of the output, just after the last sample.

time

Time of the sample pointer's current offset in the output.

Methods Summary

close()

Close task.

read([count, out])

Read a number of complete samples.

seek(offset[, whence])

Change the sample pointer position.

task(data)

tell([unit])

Current offset in the file.

Attributes Documentation

closed = False
complex_data
dtype

Data type of the output.

meta
ndim

Number of dimensions of the output.

offset = 0
sample_rate

Number of complete samples per second.

sample_shape

Shape of a complete sample.

samples_per_frame

Number of samples per frame of data.

For compatibility with file readers, to help indicate what a nominal chunk of data is.

shape

Shape of the output.

size

Number of component samples in the output.

start_time

Start time of the output.

See also time and stop_time.

stop_time

Time at the end of the output, just after the last sample.

See also start_time and time.

time

Time of the sample pointer’s current offset in the output.

See also start_time and stop_time.

Methods Documentation

close()[source] [edit on github]

Close task.

Note that this does not explicitly close the underlying source; instead, it just deletes the reference to it.

read(count=None, out=None) [edit on github]

Read a number of complete samples.

Parameters
countint or None, optional

Number of complete samples to read. If None (default) or negative, the number of samples left. Ignored if out is given.

outNone or array, optional

Array to store the samples in. If given, count will be inferred from the first dimension; the remaining dimensions should equal sample_shape.

Returns
outndarray of float or complex

The first dimension is sample-time, and the remaining ones are as given by sample_shape.

seek(offset, whence=0) [edit on github]

Change the sample pointer position.

This works like a normal filehandle seek, but the offset is in samples (or a relative or absolute time).

Parameters
offsetint, Quantity, or Time

Offset to move to. Can be an (integer) number of samples, an offset in time units, or an absolute time. For the latter two, the pointer will be moved to the nearest integer sample.

whence{0, 1, 2, ‘start’, ‘current’, or ‘end’}, optional

Like regular seek, the offset is taken to be from the start if whence=0 (default), from the current position if 1, and from the end if 2. One can alternativey use ‘start’, ‘current’, or ‘end’ for 0, 1, or 2, respectively. Ignored if offset is a time.

task(data)[source] [edit on github]
tell(unit=None) [edit on github]

Current offset in the file.

Parameters
unitUnit or str, optional

Time unit the offset should be returned in. By default, no unit is used, i.e., an integer enumerating samples is returned. For the special string ‘time’, the absolute time is calculated.

Returns
offsetint, Quantity, or Time

Offset in current file (or time at current position).