VLBIFileReaderBase

class baseband.vlbi_base.base.VLBIFileReaderBase(fh_raw)

Bases: baseband.vlbi_base.base.VLBIFileBase

VLBI wrapped file reader base class.

Typically, a subclass will define read_header, read_frame, and find_header methods. This baseclass includes a get_frame_rate method which determines the frame rate by scanning the file for headers, looking for the maximum frame number that occurs before the jump down for the next second. This method requires the subclass to define a read_header method and assumes headers have a ‘frame_nr’ item, and define a payload_nbytes property (as do all standard VLBI formats).

Parameters:

fh_raw : filehandle

Filehandle of the raw binary data file.

Attributes Summary

info	Standardized information on file readers.

Methods Summary

close()
get_frame_rate()	Determine the number of frames per second.

Attributes Documentation

info

Standardized information on file readers.

The info descriptor has a number of standard attributes, which are determined from arguments passed in opening the file, from the first header (info.header0) and from possibly scanning the file to determine the duration of frames.

Examples

The most common use is simply to print information:

>>> from baseband.data import SAMPLE_MARK5B
>>> from baseband import mark5b
>>> fh = mark5b.open(SAMPLE_MARK5B, 'rb')
>>> fh.info
File information:
format = mark5b
frame_rate = 6400.0 Hz
bps = 2
complex_data = False

missing:  nchan: needed to determine sample shape and rate.
          kday, ref_time: needed to infer full times.

>>> fh.close()

>>> fh = mark5b.open(SAMPLE_MARK5B, 'rb', kday=56000, nchan=8)
>>> fh.info
File information:
format = mark5b
frame_rate = 6400.0 Hz
sample_rate = 32.0 MHz
samples_per_frame = 5000
sample_shape = (8,)
bps = 2
complex_data = False
start_time = 2014-06-13T05:30:01.000000000
>>> fh.close()

Attributes

format	(str or None) File format, or None if the underlying file cannot be parsed.
frame_rate	(Quantity) Number of data frames per unit of time.
sample_rate	(Quantity) Complete samples per unit of time.
samples_per_frame	(int) Number of complete samples in each frame.
sample_shape	(tuple) Dimensions of each complete sample (e.g., (nchan,)).
bps	(int) Number of bits used to encode each elementary sample.
complex_data	(bool) Whether the data are complex.
start_time	(Time) Time of the first complete sample.
missing	(dict) Entries are keyed by names of arguments that should be passed to the file reader to obtain full information. The associated entries explain why these arguments are needed.

Methods Documentation

close()

get_frame_rate()

Determine the number of frames per second.

The method cycles through headers, starting from the start of the file, finding the largest frame number before it jumps back to 0 for a new second.

Returns:

frame_rate : Quantity

Frames per second.

Raises:

`EOFError`

If the file contains less than one second of data.