VDIF(VLBI Data Interchange Format) as a common data

format in e-VLBI era.

M. Sekido (NICT)M.Kettenis(ATNF), C.Phillips(JIVE),

A.Whitney(MIT/Haystack),Y.Koyama(NICT), H.Harai(NICT)

East-Asia VLBI Workshop 18 Mar. 2009 @ Korea

Compatibility between VLBI systems has been a headache issue for a long time.

K3,Mark3,VLBA

K4,VSOP

S2

Standard interface:VSI-H, VSI-S, VSI-E

Sam

ple

r

DIM DOM

VSI-H VSI-H

VSI-S

VSI-EVSI-E

Co

rrelator

E-VLBI

VSI-HVSI-H

RTP/RTCP

ADS1000

Mark5B

VOA-200 VOA-200

Network

eVLBI: Data transport media has replaced by HDD/network.

Mark5B

Correlation Agent(Cor_srv2.pl)Correlation Agent

(Cor_srv2.pl)Correlation Agent(Cor_srv2.pl)Correlation Agent

(Cor_srv2.pl)

Network

K5

Mk5

Correlators:Soft/Hard

Standard Data format (VDIF)

Discussion in eVLBI WS@Shanghai(2008)

Task Force member (A.Whitney, M.Kettenis, C.Phillips, M.Sekido) as regional representatives have discussed by E-mail.

Asia（ NICT)

Asia（ NICT)

Australia(ATNF)

Australia(ATNF)

USA(Haystack)

USA(Haystack)

Europe(JIVE)

Europe(JIVE)

VDIFTask Force

VDIFTask Force

VDIFVDIF

SHAO NAOJ KA 냐

NRAO

EVN

”standardized transport-independent VLBI data-interchange format that is suitable for all types of VLBI data transfer, including real-time and near-real-time e-VLBI, as well as disk-file storage.”

VDIF

Protocol （ TCP/IP,UDP/IP, etc…,data file) is not defined, this time. You can use any…

Data format (contents in frames) is defined

DAS Correlator

32b

it/word

Data

Header

Data

Header

Data

Header

Basic Structure = Frame format

VDIFVDIF

Possible Usage of VDIF:

File File

D H D H D H D H D H D H

FTP,HTTP,Tsunami,or any otherD H D H D H

single stream of Multi-channel data

VDIFVDIF

Multi (single-channel) streams to different destinations

D HD HD H

D HD HD H

D HD HD H

Header FormatInvalid flag Legacy

mode:16byte or 32byte header

Half Year Counter since 2000.0

Sequencial #Frame

Frame size

Complex flag

Version No.

Extended Version

Bit

Nch

ID for multi-stream

Station ID

User Defined header field

VDIFVDIF

Data format1bit/sample

2bit/sample

3bit/sample

4bit/sample

VDIFVDIF

Data format (Complex data)

1bit/sample

2bit/sample

3bit/sample

4bit/sample

VDIFVDIF

VDIF Data Stream Format Designator

1024-16-2-1 ⇒ 32Msps-2bit-16ch 1024-16-2-4 ⇒ 32Msps-2bit-16ch

via 4ch-4 streams

VDIFVDIF

threads#Bit/Samplech# TotalRate Data Total

2Designator1Designator

1024-16-2+64-8-8 ⇒ 32Msps-2bit-16ch stream + 1Msps-8bit-8ch

stream

Summary

VDIF has a scope of Transport Independent Standard VLBI

Data Format Wide Flexibility for VLBI Applications

(Geodesy, Astronomy, Spacecraft) Multi stream for distributed processing

Standard Transport Protocol may be discussed in the next.

VDIFVDIF