Mark5BStreamReader

class baseband.mark5b.base.Mark5BStreamReader(fh_raw, sample_rate=None, kday=None, ref_time=None, nchan=None, bps=2, squeeze=True, subset=(), fill_value=0.0, verify='fix')[source] [edit on github]

Bases: baseband.mark5b.base.Mark5BStreamBase, baseband.base.base.VLBIStreamReaderBase

VLBI Mark 5B format reader.

Allows access a Mark 5B file as a continues series of samples.

Parameters
fh_rawfilehandle

Filehandle of the raw Mark 5B stream.

sample_rateQuantity, optional

Number of complete samples per second, i.e. the rate at which each channel is sampled. If None (default), will be inferred from scanning one second of the file or, failing that, using the time difference between two consecutive frames.

kdayint or None

Explicit thousands of MJD of the observation start time (eg. 57000 for MJD 57999), used to infer the full MJD from the header’s time information. Can instead pass an approximate ref_time.

ref_timeTime or None

Reference time within 500 days of the observation start time, used to infer the full MJD. Only used if kday is not given.

nchanint

Number of channels. Needs to be explicitly passed in.

bpsint, optional

Bits per elementary sample. Default: 2.

squeezebool, optional

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

subsetindexing object, optional

Specific channels of the complete sample to decode (after possible squeezing). If an empty tuple (default), all channels are read.

fill_valuefloat or complex

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

verifybool or ‘fix’, optional

Whether to do basic checks of frame integrity when reading. Default: ‘fix’, which implies basic verification and replacement of gaps with zeros.

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()

read([count, out])

Read a number of complete samples.

readable()

Whether the file can be read and decoded.

seek(offset[, whence])

Change the sample pointer position.

tell([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__).

ndim

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

sample_rate
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() [edit on github]
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.

readable() [edit on github]

Whether the file can be read and decoded.

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.

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).