VLBI Data Interchange Format

A. Whitney1, M. Kettenis2, C. Phillips3 and M. Sekido4

1MIT Haystack Observatory, USA
2Joint Institute for VLBI in Europe, The Netherlands
3CSIRO/ATNF, Australia
4Mamoru Sekido, NICT, Japan

Oral presentation

One important outcome of the 7th International e-VLBI Workshop in Shanghai in June 2008 was the creation of a task force to study and recommend a universal VLBI data format that is suitable for both on-the-wire e-VLBI data transfer, as well as direct disk storage.  This task force, called the VLBI Data Interchange Format (VDIF) Task Force, is envisioned as the first part of a two part effort, the second of which will address standardization of e-VLBI data-transmission-protocols.  The formation of the VDIF Task Force was prompted particularly by increased e-VLBI activity and the difficulties encountered when data arrive at a correlator in different formats from various instruments in various parts of the world.  The task force has proposed a streaming packetized data format that may be used for real-time and non-real-time e-VLBI, as well as direct disk storage.  The data may contain multiple channels of time-sampled data with an arbitrary number of channels, arbitrary #bits/sample up to 32, 'real' or 'complex' data; data rates in excess of 100Gbps are supported.  Each data packet is completely self-identifying via a short header, and data may be decoded without reference to any external information.  The VDIF task force expects to present a final report to the VLBI community in early 2009.