1. 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

2. Compatibility between VLBI systems has been a headache issue for a long time. K3,Mark3,VLBA K4,VSOP S2

3. Standard interface: VSI-H, VSI-S, VSI-E Sampler DIMDOM VSI-H VSI-S VSI-E Correlator E-VLBI VSI-H RTP/RTCP ADS1000 Mark5B VOA-200

4. 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

5. 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. VDIF SHAO NAOJ KA 냐 NRAO EVN

6. ”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 32bit/word Data Header Data Header Data Header Basic Structure = Frame format VDIF

7. Possible Usage of VDIF: File D H D H D H D H D H D H FTP,HTTP,Tsunami,or any other D H D H D H single stream of Multi-channel data VDIF Multi (single-channel) streams to different destinations D H D H D H D H D H D H D H D H D H

8. Header Format Invalid 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 VDIF

9. Data format 1bit/sample 2bit/sample 3bit/sample 4bit/sample VDIF

10. Data format (Complex data) 1bit/sample 2bit/sample 3bit/sample 4bit/sample VDIF

11. VDIF Data Stream Format Designator 1024-16-2-1 ⇒ 32Msps-2bit-16ch 1024-16-2-4 ⇒ 32Msps-2bit-16ch via 4ch-4 streams VDIF 1024-16-2+64-8-8 ⇒ 32Msps-2bit-16ch stream + 1Msps-8bit-8ch stream

12. 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. VDIF