GSBStreamWriter

class baseband.gsb.base.GSBStreamWriter(fh_ts, fh_raw, header0=None, sample_rate=None, samples_per_frame=None, payload_nbytes=None, nchan=None, bps=None, complex_data=None, squeeze=True, **kwargs)

Bases: baseband.gsb.base.GSBStreamBase, baseband.vlbi_base.base.VLBIStreamWriterBase

GSB format writer.

Encodes and writes sequences of samples to file.

Parameters:

fh_ts : GSBTimeStampIO

For writing headers to storage.

fh_raw : filehandle, or nested tuple of filehandles

For writing raw binary data to storage. A single file is needed for rawdump, and a tuple for phased. For a nested tuple, the outer tuple determines the number of polarizations, and the inner tuple(s) the number of streams per polarization. E.g., ((polL1, polL2), (polR1, polR2)) for two streams per polarization. A single tuple is interpreted as streams of a single polarization.

header0 : GSBHeader

Header for the first frame, holding time information, etc. Can instead give keyword arguments to construct a header (see **kwargs).

sample_rate : Quantity, optional

Number of complete samples per second, i.e. the rate at which each channel of each polarization is sampled. If not given, will be inferred assuming the frame rate is exactly 0.25165824 s.

samples_per_frame : int, optional

Number of complete samples per frame. Can give payload_nbytes instead.

payload_nbytes : int, optional

Number of bytes per payload, divided by the number of raw files. If both samples_per_frame and payload_nbytes are None, payload_nbytes is set to 2**22 (4 MB) for rawdump, and 2**23 (8 MB) divided by the number of streams per polarization for phased.

nchan : int, optional

Number of channels. Default: 1 for rawdump, 512 for phased.

bps : int, optional

Bits per elementary sample, i.e. per real or imaginary component for complex data. Default: 4 for rawdump, 8 for phased.

complex_data : bool, optional

Whether data are complex. Default: False for rawdump, True for phased.

squeeze : bool, optional

If True (default), write accepts squeezed arrays as input, and adds any dimensions of length unity.

**kwargs

If no header is given, an attempt is made to construct one from these. For a standard header, this would include the following.

— Header keywords : (see fromvalues())

time : Time

Start time of the file.

header_mode : ‘rawdump’ or ‘phased’, optional

Used to explicitly set the mode of the GSB stream. Default: ‘rawdump’ if only a single raw file is present, or ‘phased’ otherwise.

seq_nr : int, optional

Frame number, only used for phased (default: 0).

Attributes Summary

bps	Bits per elementary sample.
complex_data	Whether the data are complex.
header0	First header of the file.
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.
squeeze	Whether data arrays have dimensions with length unity removed.
start_time	Start time of the file.
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()
flush()
tell([unit])	Current offset in the file.
write(data[, valid])	Write data, buffering by frames as needed.

Attributes Documentation

bps

Bits per elementary sample.

complex_data

Whether the data are complex.

header0

First header of the file.

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.

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.

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()

flush()

tell(unit=None)

Current offset in the file.

Parameters:

unit : Unit 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:

offset : int, Quantity, or Time

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

write(data, valid=True)

Write data, buffering by frames as needed.

Parameters:

data : ndarray

Piece of data to be written, with sample dimensions as given by sample_shape. This should be properly scaled to make best use of the dynamic range delivered by the encoding.

valid : bool, optional

Whether the current data are valid. Default: True.