What is format of DAXIQ data?

AB4EJ

When I activate DAXIQ data on a slice, I understand per the wiki that the DAXIQ data is sent via UDP port 4991. However, I have not been able to find a low-level description of the format of the IQ data. Specific questions:
- how many IQ samples are in each buffer sent?
- what format are the IQ samples?  I & Q values, each 32-bit floating point (such as IEEE 754 single precision, or what?
- what is the endianess of the data? Do I have to rotate the bits or something to work with it in fftw?
Sorry if this is answered elsewhere, I have not found it so far.

Dan-N7HQ

Bill,

It's streamed in VITA-49 format.  Please see http://wiki.flexradio.com/index.php?title=SmartSDR_Ethernet_API

Here is an excellent community discussion with FlexRadio engineering about the data within the VITA-49 envelope.
https://community.flexradio.com/flexradio/topics/iq_stream_from_6700_radio


73,
Dan

AB4EJ

Dan - I have looked at the wiki article you cited; it does not explain the VITA-49 format, nor does it include a link to an online specification.  I have done quite a bit of online searching for the spec, but all I have found so far is general discussions of it that don't get into the details; could anyone point me to the specification itself?

A second question: using SmartSDR, I activate a DAXIQ stream both in the panadapter slice and also in DAX; then I look for UDP traffic on port 4991. Is this right? Because (using tcpdump or windump) it looks like all the same traffic is on that port with or without a DAXIQ stream activated. Does DAX wait for a connect/bind command or something before it starts streaming on port 4991?

Geoff AB6BT

The protocol is in here (Page 9):
https://www.redrapids.com/images/documents/REF-004-002-R02.pdf

Does that help?

AB4EJ

Geoff:  Thanks, it does help!  Quick question: have you run across an already coded data structure (C, C++ or C#) for the Signal Data Packet?  I can code it, but this could save some time...

Geoff AB6BT

Hi Bill, no sorry I don't.

Dan-N7HQ

The full specification is available from the VSO (Vita Standards Org) 

https://www.vita.com/Standards