Exporting back to CTF tools

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Mon Mar 19 21:40:58 CET 2007

Hi Niki

On 19 Mar 2007, at 18:03, Niki Ray wrote:
>   I want to use the CTF tools to do a SAM analysis, but want to
> first run
> the  ICA in fieldtrip. Is it possible to export data back into the
> format
> required by the CTF SAMsuite after preprocessing in fieldtrip?

We do not have tools to write CTF data. However, the CTF meg4 format
is very simple. As long as you apply the same (inverse) amplitude
calibration and convert the double data back to int32, it should be
possible to insert the processed values back into a CTF meg4 file.
You can have a look at fieldtrip/private/read_ctf_meg4.m and try to
reverse-engineer the reading function. The code looks more complex
than it is, that is due to the multi-file handling (files cannot be
larger than 2GB).

If I recall correctly, the meg4 file consists of a 8 byte header,
followed by blocks of data. Each block is hdr.nSamples*hdr.nChans*4
butes large. Within a block the data is not multiplexed, but instead
one channel after the other.

best regards,

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