Wavecom PXGF streaming format (GEW) V1.24 - Manual (Page 10)

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GSY-0D8-SE RESTRICTED Interface Requirement Specification for PXGF Streaming and File Format
use other chunks. The only constraint here is that files must start with a “SOFH chunk”. Due to
the sequential nature of parsing and the inability to nest chunks, a separate global chunk is
needed to identify the end of the file header, namely the "EOFH" chunk.
3.3 APPLICATION NOTES
Above is a graphical illustration showing how PXGF chunks of different type are ordered in a
stream/file. Below are some notes to the developer to keep in mind when using the PXGF format in an
application.
1. The PXGF framework for streaming and storage is designed to be extensible. Different
applications require different information and if this information is not available in a stream,
then that application will not be able to process that stream successfully. Just because an
application uses the PXGF format doesn't mean that it will be able to process all PXGF
streams or files. For a particular project care should be taken to ensure that all necessary
chunks are included.
2. It is recommended that meta data like the sample rate and packing description be sent every
second. This allows state information to be recovered if synchronisation is lost and makes it
possible to process large files from the middle of the file.
3. Only data from one data source and of one format must be included in each stream or file.
Current formats include "SSIQ" for single channel data and "GSIQ" for multi-channel data. The
format used in files should be indicated using the SOFH chunk. The format name may also be
used for the file extension to allow visual discrimination of different files.
4. State information is accumulated by an application by reading different chunks sequentially. If
synchronisation is lost, state information needs to be reset. This is why it is essential to
resend meta data every second.
5. It is necessary to be able to distinguish between continuous data and block data where only
part of the time data is available. Data chunks contain timestamps to enable detection of
discontinuities. A chunk has also been defined to indicate discontinuities in the time data,
namely the "IQDC" chunk.
6. Playback control is essential for the off-line analysis of files, however due to the stream based
design of the PXGF format, playback control is not easily supported. The PXGF format uses
data chunks supported by a number of meta chunks that describe the state of the data stream.
Products
2009-01-13 RESTRICTED Page 9
Issue 1.24
Figure 1: Example chunk usage in a PXGF stream