Dear PDL-List,
I have a binary file that I need to extract information. Before
coming to
PDL::IO::FlexRaw I had been trying (w/o success) to get this file
read with
Perl functions read/unpack. This was proving tedious -- like picking up
freshly caught sardines on stainless steel with your elbows. Possibly
that
was foreseeable, nonetheless, I scooped the Perl monks with a query
and they
pointed out the obvious, ``why not use PDL::IO::FlexRaw''. Alas, this
module
seems rife with possibility for slurping what I need into piddles and
then
doing what I want with the piddles. Unfortunately I cannot make out the
format of the header file. Does it take signed and unsigned integers
(16,32,64 bit) ? How about IEEE compliant floats?
More directly, can someone that knows FlexRaw have a look below at the
outline of the format for the binary files that I have and suggest a
header
template?
I have tried the following, but this is not exactly right, and I'm a
little
in the dark on how to proceed given the documentation (FlexRaw) doesn't
outline a general case for the header file, rather just an example for
Fortran 77, which my binary files are not ... my attempt:
my $header = [
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 1, Dims => [ 4 ] },
{ Type => 'byte', NDims => 80, Dims => [ 512 ] },
{ Type => 'byte', NDims => 80, Dims => [ 512 ] },
{ Type => 'byte', NDims => 80, Dims => [ 512 ] },
{ Type => 'byte', NDims => 80, Dims => [ 512 ] },
{ Type => 'byte', NDims => 80, Dims => [ 512 ] },
{ Type => 'byte', NDims => 80, Dims => [ 512 ] },
{ Type => 'byte', NDims => 80, Dims => [ 512 ] }
];
my @dat = readflex($file,$header);
And now the complete description of the file:
# HEADER:
# Each File has two major sections. A Header section and a Data
section.
The Header section is as follows:
# - The header is expandable. Each newer version also contains the
information used the by older version.
# - When reading a CrossSpectra file that is a newer version
than you
expect then use the Extent field to skip to the beginning of the cross
spectra data.
# - The following Header description is a set of data fields in
order
where each field description is a value type with implied size,
followed by
the field name, and followed by the fieldʼs description.
# * Note. If version is 3 or less, then nRangeCells=31,
nDopplerCells=512, nFirstRangeCell=1
#
# Version 1:
# * SInt16 -> nCsaFileVersion -> File Version 1 to latest. (If
greater
than 32, itʼs probably not a spectra file.)
# * UInt32 -> nDateTime -> TimeStamp. Seconds from Jan 1,1904
local
computer time at site. The timestamp for CSQ files represents the
start time
of the data (nCsaKind = 1). The timestamp for CSS and CSA files is the
center time of the data (nCsaKind = 2).
# * SInt32 -> nV1Extent -> Header Bytes extension (Version 4
is +62
Bytes Till Data)
#
# Version 2:
# * SInt16 -> nCsKind -> Type of CrossSpectra Data. 1 is self
spectra
for all used channels, followed by cross spectra. Timestamp is start
time of
data. 2 is self spectra for all used channels, followed by cross
spectra,
followed by quality data. Timestamp is center time of data.
# * SInt32 -> nV2Extent -> Header Bytes extension (Version 4
is +56
Bytes Till Data)
#
# Version 3:
# * Char4 -> nSiteCodeName -> Four character site code 'site'
# * SInt32 -> nV3Extent -> Header Bytes extension (Version 4
is +48
Bytes Till Data)
#
# Version 4:
# * SInt32 -> nCoverageMinutes -> Coverage Time in minutes for
the
data. ʻCSQ' is normally 5minutes (4.5 rounded). 'CSS' is normally
15minutes
average. 'CSA' is normally 60minutes average.
# * SInt32 -> bDeletedSource -> Was the ʻCSQ' deleted by CSPro
after
reading.
# * SInt32 -> bOverrideSourceInfo -> If not zero, CSPro used
its own
preferences to override the source ʻCSQʼ spectra sweep settings.
# * Float -> fStartFreqMHz -> Transmit Start Freq in MHz
# * Float -> fRepFreqHz -> Transmit Sweep Rate in Hz
# * Float -> fBandwidthKHz -> Transmit Sweep bandwidth in kHz
# * SInt32 -> bSweepUp -> Transmit Sweep Freq direction is up
if non
zero, else down. NOTE: CenterFreq is fStartFreqMHz + fBandwidthKHz/2 *
-2^(bSweepUp==0)
# * SInt32 -> nDopplerCells -> Number of Doppler Cells
(nominally 512)
# * SInt32 -> nRangeCells -> Number of RangeCells (nominally
32 for
ʻCSQ', 31 for 'CSS'& 'CSA')
# * SInt32 -> nFirstRangeCell -> Index of First Range Cell in
data from
zero at the receiver. ʻCSQ' files nominally use zero. 'CSS' or 'CSA'
files
nominally use one because CSPro cuts off the first range cell as
meaningless.
# * Float -> fRangeCellDistKm -> Distance between range cells in
kilometers.
# * SInt32 -> nV4Extent -> Header Bytes extension (Version 4
is +0
Bytes Till Data)
#
# Version 5:
# * SInt32 -> nOutputInterval -> The Output Interval in Minutes.
# * Char4 -> nCreatorTypeCode -> The creator application type
code.
# * Char4 -> nCreatorVersion -> The creator application version.
# * SInt32 -> nActiveChannels -> Number of active antennas
# * SInt32 -> nSpectraChannels -> Number antenna used in cross
spectra
# * UInt32 -> nActiveChannelBits -> Bit indicator of which
antennas are
in use msb is ant#1 to lsb #32
# * SInt32 -> nV5Extent -> Header Bytes extension (Version 5
is +0
Bytes Till Data) If zero then cross spectra data follows, but if this
file
were version 6 or greater then the nV5Extent would tell you how many
more
bytes the version 6 and greater uses until the data.
#
# DATA:
# The data section is a multi-dimensional array of self and cross
spectra
data.
# Repeat For 1 to nRangeCells:
# * Float[nDopplerCells] Antenna1 voltage squared amplitude self
spectra.
# * Float[nDopplerCells] Antenna2 voltage squared amplitude self
spectra.
# * Float[nDopplerCells] Antenna3 voltage squared amplitude self
spectra.
# (Warning: Some Antenna3 amplitude values may be negative to
indicate noise or interference at those doppler bins. These negative
values
should be absoluted before use.)
# * Complex[nDopplerCells] Antenna 1 to Antenna 2 cross spectra.
# * Complex[nDopplerCells] Antenna 1 to Antenna 3 cross spectra.
# * Complex[nDopplerCells] Antenna 2 to Antenna 3 cross spectra.
# if nCsaKind is 2 then also read or skip
# * Float[nDopplerCells] Quality array from zero to one in value.
# End Repeat
#
# Note: To convert self spectra to dBm use:
# 10*log10(abs(voltagesquared)) - (-40. + 5.8)
* *
# The -40. is conversion loss in the receiver and +5.8 is
processing
computational gain.
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