[Difx-users] Multi-thread 4-bit VDIF fails with 'vdifmux() failed with return code -2014' {External}

[Jacob Brooks]

Hi all,

We're currently trying to get DiFX working with the following setup: 4-bit, 2 channel (L + R pols), 2 threads (2 subbands), delivered in real time via UDP. It has been working fine up until the point where we tried adding a second thread - single-thread VDIF has been working for us.

When running in multi-threaded mode, the datastream processes crash with the following message:

'vdifmux() failed with return code -2014, likely input buffer is too small!'

I have managed to trace the problem to a check in 'getLowestFrameNumber' in vdifio/src/vdifmux.c. The inequality check in that function:

'getVDIFNumChannels(vh) != vm->inputChannelsPerThread'

succeeds as the function returns a value of 2 while 'inputChannelsPerThread' has a value of 1. This happens for every iteration so vdifmux() fails and returns a -2014 error code.

I'm not sure where to go from here and was hoping someone more familiar with DiFX could help out. Hopefully I'm not missing something obvious! If you need any more information I haven't provided please do ask.

Cheers,
Jake
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