VDIFStreamReader

class baseband.vdif.base.VDIFStreamReader(fh_raw, sample_rate=None, squeeze=True, subset=(), fill_value=0.0, verify='fix')

Bases: baseband.vdif.base.VDIFStreamBase, baseband.vlbi_base.base.VLBIStreamReaderBase

VLBI VDIF format reader.

Allows access to a VDIF file as a continuous series of samples.

Parameters

fh_rawfilehandle

Filehandle of the raw VDIF stream.

sample_rateQuantity, optional

Number of complete samples per second, i.e. the rate at which each channel in each thread is sampled. If None (default), will be inferred from the header or by scanning one second of the file.

squeezebool, optional

If True (default), remove any dimensions of length unity from decoded data.

subsetindexing object or tuple of objects, optional

Specific components of the complete sample to decode (after possible squeezing). If a single indexing object is passed, it selects threads. If a tuple is passed, the first selects threads and the second selects channels. If the tuple is empty (default), all components are read.

fill_valuefloat or complex, optional

Value to use for invalid or missing data. Default: 0.

verifybool, optional

Whether to do basic checks of frame integrity when reading. The first frameset of the stream is always checked. Default: True.

Attributes Summary

bps	Bits per elementary sample.
complex_data	Whether the data are complex.
dtype
fill_value	Value to use for invalid or missing data.
header0	First header of the file.
info()	Standardized information on stream readers.
ndim	Number of dimensions of the (squeezed/subset) stream data.
sample_rate	Number of complete samples per second.
sample_shape	Shape of a complete sample (possibly subset or squeezed).
samples_per_frame	Number of complete samples per frame.
shape	Shape of the (squeezed/subset) stream data.
size	Total number of component samples in the (squeezed/subset) stream data.
squeeze	Whether data arrays have dimensions with length unity removed.
start_time	Start time of the file.
stop_time	Time at the end of the file, just after the last sample.
subset	Specific components of the complete sample to decode.
time	Time of the sample pointer’s current offset in file.
verify	Whether to do consistency checks on frames being read.

Methods Summary

close(self)
read(self[, count, out])	Read a number of complete (or subset) samples.
readable(self)	Whether the file can be read and decoded.
seek(self, offset[, whence])	Change the stream position.
tell(self[, unit])	Current offset in the file.

Attributes Documentation

bps

Bits per elementary sample.

complex_data

Whether the data are complex.

dtype

fill_value

Value to use for invalid or missing data. Default: 0.

header0

First header of the file.

info

Standardized information on stream readers.

The info descriptor provides a few standard attributes, most of which can also be accessed directly on the stream filehandle, and tests basic readability of the stream. More detailed information on the underlying file is stored in its info, accessible via info.file_info (and shown by __repr__).

Attributes

start_timeTime

Time of the first complete sample.

stop_timeTime

Time of the complete sample just beyond the end of the file.

sample_rateQuantity

Complete samples per unit of time.

shapetuple

Equivalent shape of the whole file, i.e., combining the number of complete samples and the shape of those samples.

bpsint

Number of bits used to encode each elementary sample.

complex_databool

Whether the data are complex.

verifybool or str

The type of verification done by the stream reader.

readablebool

Whether the first and last samples could be read and decoded.

checksdict

Checks that were done to determine whether the file was readable (normally ‘continuous’ and ‘decodable’).

errorsdict

Any exceptions raised while trying to determine attributes or doing checks. Keyed by the attributes/checks.

warningsdict

Any warnings about the attributes or about the checks. Keyed by the attributes/checks.

ndim

Number of dimensions of the (squeezed/subset) stream data.

sample_rate

Number of complete samples per second.

sample_shape

Shape of a complete sample (possibly subset or squeezed).

samples_per_frame

Number of complete samples per frame.

shape

Shape of the (squeezed/subset) stream data.

size

Total number of component samples in the (squeezed/subset) stream data.

squeeze

Whether data arrays have dimensions with length unity removed.

If True, data read out has such dimensions removed, and data passed in for writing has them inserted.

start_time

Start time of the file.

See also time for the time of the sample pointer’s current offset, and (if available) stop_time for the time at the end of the file.

stop_time

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

See also start_time for the start time of the file, and time for the time of the sample pointer’s current offset.

subset

Specific components of the complete sample to decode.

The order of dimensions is the same as for sample_shape. Set by the class initializer.

time

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

See also start_time for the start time, and (if available) stop_time for the end time, of the file.

verify

Whether to do consistency checks on frames being read.

Methods Documentation

close(self)

read(self, count=None, out=None)

Read a number of complete (or subset) samples.

The range retrieved can span multiple frames.

Parameters

countint or None, optional

Number of complete/subset samples to read. If None (default) or negative, the whole file is read. Ignored if out is given.

outNone or array, optional

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

Returns

outndarray of float or complex

The first dimension is sample-time, and the remainder given by sample_shape.

readable(self)

Whether the file can be read and decoded.

seek(self, offset, whence=0)

Change the stream 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.

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.

tell(self, unit=None)

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).