TDMS Extract Segments

Question

So I'm learning a lot about the TDMS file structure using this document.
http://www.ni.com/white-paper/5696/en/
My goal is to be able to break up a TDMS file into its segments, or rather break up a file that has 2000 segments, into 100 files with 20 segments in them each.  Opening a TDMS file into a hex editor I can see all the segments, and I can save the first 20 Segment on its own into a new file and it opens just fine in the Excel import.  But if I try to take the second 20 Segment (without the first 20) and save it away the Excel Import craps out with a code 6.  I tried just taking segment 21 and it also dies in a similar way.  Attached is the original fragmented file which should have 40 segments, the file split into the first 20, the second 20 and a file with just the 21st.
So my question is this.  What am I doing wrong in the split process?  Why does segment 21 on its own create an invalid TDMS file?
EDIT: I also tried deleting the index files forcing them to be recreated.
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Attachments:
Segment Extract Test.zip ‏4 KB

Answer 1

Hi, 
It's not quite common for splitting a TDMS file by segment numbers. I just try to explain your two questions. 
1."What am I doing wrong in the split process? "
As your description, I think when you create the TDMS file containing the second 20 segments or only the 21 segment, you simply copied the binary from the original file. The binary for the second 20 segments(and the 21 segment) is relative with the binary in previous. The binary you copied for latter segments is lack of some parts(details explained in question 2), so can not compose a valid TDMS file format. But the binary for the first 20 segments is intergrated for a valid TDMS file format. That's why you can just successfully open the TDMS file containing the first 20 segments.
2."Why does segment 21 on its own create an invalid TDMS file?" 
As a conclusion, the binary of "21st Segment.tdms" is lack of the parts below in Meta Data:
  1) The root object and group object ;
       From the binary snapshot of "21st Segment.tdms", we can see there is no binary for root object and group object in Meta Data part(Address 0x1c ~ 0x3d).
  2) Details of raw data index for the channel object.
       The snapshot shows Raw Data Index part in Meta Data is 0x 00 00 00 00(Address 0x36~0x39), that means the raw data index of the object in this segment exactly matches the index the same object had in the previous segment. But for an independent TDMS file, this part can not be omitted. The missing part is identical with the part of Address 0x6b ~ 0x7e in the snapshot of the 1st segment.
If the above parts are added in Meta Data, the next segment offset and raw data offset in Lead In(Address 0x0c~0x13 and 0x14~0x1b in the binary of "21st Segment.tdms") should also be updated.
The binary of "21st Segment.tdms":
The binary of the 1st segment(within the red frame):