Wavecom PXGF streaming format (GEW) V1.24 - Manual (Page 11)

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GSY-0D8-SE RESTRICTED Interface Requirement Specification for PXGF Streaming and File Format
Before processing data chunks it is necessary to obtain sufficient state information, like the
sample rate, by processing the necessary chunks in the data stream.
The use of an index file has been proposed as a possible solution to the problem of playback
control. By reading an index file an application could determine over what period the recording
was made and determine where to start processing the stream to play back a particular
section.
7. C++ and Java libraries have been developed for the writing and reading of PXGF streams.
The libraries take care of synchronisation and formatting issues; they do not provide or dictate
the communication medium.
8. The PXGF streaming format does not provide any mechanism for communication between the
source of the data stream and the application receiving the data stream. The PXGF stream
therefore represents a unidirectional flow of information from the source to the sink of the
stream.
9. Applications that process PXGF input streams should not make assumptions about the data.
For example, if the sample data were being sent using the SSIQ chunk the application should
wait for a SIQP chunk to determine the packing of the data rather than assuming a particular
packing.
3.4 DEFINITION OF CHUNKS
3.4.1 Single channel Short IQ time data – SSIQ chunk
Data is assumed to be continuous when using this data format, if the data is blocky, an IQDC chunk
must be sent after every block of continuous data.
Element Type Description
lTimestamp int64 The timestamp is stored as a 64 bit signed number,
representative of the time of capture of the first sample in the
chunk block, in microsecond resolution. It is stored as the
number of microseconds since beginning of the epoch (i.e. 1st
January 1970 midnight).
awIQData int16[length of IQ
data
array]
IQ pairs of signed int16 short numbers. Note that regardless of
the number of valid bits, the most significant bits in each short
should be used. This allows us to specify the full-scale level
without needing to specify the number of bits.
Table 3.2: The SSIQ chunk
3.4.2 Single channel IQ Packing – SIQP chunk
The information in this chunk is required to parse the data in the SSIQ chunk.
Element Type Description
iIsIQPacked int32 Value 1 for IQ ordering and
value 0 for QI ordering. For
example: a value of 1 will
indicate that the first sample in
the element awIQData of a SSIQ
chunk is an “I” sample.
Table 3.3: The SIQP chunk
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2009-01-13 RESTRICTED Page 10
Issue 1.24