Mark5BFileReader

class baseband.mark5b.base.Mark5BFileReader(fh_raw, kday=None, ref_time=None, nchan=None, bps=2)

Bases: baseband.vlbi_base.base.VLBIFileReaderBase

Simple reader for Mark 5B files.

Wraps a binary filehandle, providing methods to help interpret the data, such as read_frame and get_frame_rate.

Parameters

fh_rawfilehandle

Filehandle of the raw binary data file.

kdayint or None

Explicit thousands of MJD of the observation time. Can instead pass an approximate ref_time.

ref_timeTime or None

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

nchanint, optional

Number of channels. Default: 1.

bpsint, optional

Bits per elementary sample. Default: 2.

Attributes Summary

info()

Methods Summary

close(self)
find_header(self[, forward, maximum])	Find the nearest header from the current position.
get_frame_rate(self)	Determine the number of frames per second.
read_frame(self[, verify])	Read a single frame (header plus payload).
read_header(self)	Read a single header from the file.
temporary_offset(self)	Context manager for temporarily seeking to another file position.

Attributes Documentation

info

Methods Documentation

close(self)

find_header(self, forward=True, maximum=None)

Find the nearest header from the current position.

If successful, the file pointer is left at the start of the header.

Parameters

forwardbool, optional

Seek forward if True (default), backward if False.

maximumint, optional

Maximum number of bytes to search through. Default: twice the frame size of 10016 bytes.

Returns

headerMark5BHeader or None

Retrieved Mark 5B header, or None if nothing found.

get_frame_rate(self)

Determine the number of frames per second.

This method first tries to determine the frame rate by looking for the highest frame number in the first second of data. If that fails, it uses the time difference between two consecutive frames. This can fail if the headers do not store fractional seconds, or if the data rate is above 512 Mbps.

Returns

frame_rateQuantity

Frames per second.

read_frame(self, verify=True)

Read a single frame (header plus payload).

Returns

frameMark5BFrame

With header and data properties that return the Mark5BHeader and data encoded in the frame, respectively.

verifybool, optional

Whether to do basic checks of frame integrity. Default: True.

read_header(self)

Read a single header from the file.

Returns

headerMark5BHeader

temporary_offset(self)

Context manager for temporarily seeking to another file position.

To be used as part of a with statement:

with fh_raw.temporary_offset() [as fh_raw]:
    with-block

On exiting the with-block, the file pointer is moved back to its original position.