Can I just check: are you sure that the original
tmp.tck file didn’t also have the same
count field of 69114? It’s actually pretty rare for these two fields to match – the
total_count field refers to the total number of streamlines successfully seeded, but many won’t survive the various tests subsequently applied (minimum length, include/exclude, etc.)… It doesn’t refer to the number of streamlines actually in the file itself.
If you can confirm that the
count field genuinely doesn’t match before and after conversion, then we’ll need to investigate. Also, please try running
tckinfo -count: this forces an explicit count of the streamlines in the file, rather than merely reporting the value in the header.