[Difx-users] VEX $TRACK fanout_def for 8-bit data? {External}

[Phillips, Chris (S&A, Marsfield)]

Hi Jan,

I believe DIFX basically ignores this anyhow and certainly has no way to handle arbitrary  “track” mapping, (ie all 8 bit have to be contagious). I may have forgotten the details, but I am pretty sure “CH01” is assumed to be the first channel, so I don’t think it matters much. Certainly I never create a proper track mapping and definitely not with all 8 bits defined.

Cheers
Chris


On 3 Nov 2023, at 21:43, Jan Wagner via Difx-users <difx-users at listmgr.nrao.edu> wrote:

Hi list,

vex2difx has gotten pickier about VEX syntax, when a VDIF station is missing fanout_def's from $TRACK the station is dropped from correlation.

With 1-bit or 2-bit VDIF recordings the $TRACK fanout_def's work. For 8-bit VDIF data, however, vex2difx complains "Note: getBits: Mode=... differing number of bits: 8,2" and that "some metadata may be incorrect".

v2d:
format=VDIF/8224/8

VEX:
def VDIF.1Ch8bit1to1;
     track_frame_format = VDIF8224;
     fanout_def =   : &CH01 : sign : 1:  1;
     fanout_def =   : &CH01 :  mag : 1:  2;
     fanout_def =   : &CH01 :  mag : 1:  3;
     fanout_def =   : &CH01 :  mag : 1:  4;
     fanout_def =   : &CH01 :  mag : 1:  5;
     fanout_def =   : &CH01 :  mag : 1:  6;
     fanout_def =   : &CH01 :  mag : 1:  7;
     fanout_def =   : &CH01 :  mag : 1:  8;
enddef;

Is there a correct way to declare it?

I didn't find any mention of 8-bit (or 4-bit, or 2-bit Complex) or generic cases under https://safe.nrao.edu/wiki/bin/view/VLBA/Vex2doc

regards,
Jan
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