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ali1234 / vhs-teletext

Software to recover teletext data from VHS recordings.
GNU General Public License v3.0
179 stars 21 forks source link

Bring back the old squashing algorithm from V1 #54

Open ali1234 opened 4 years ago

ali1234 commented 4 years ago

In V1, subpages would be compared and only squashed if some percentage of characters (not including whitespace) were a match.

This code was removed when testing showed that the deconvolution algorithm had become good enough to nearly always get the correct subpage code. However, it turns out that often the subpage codes are not broadcast correctly - either every subpage is "0001", or it can be used for another purpose.

The upshot of this is that those broadcasts won't squash correctly in V3 because completely different subpages get squashed together, which ruins them.

So this issue is about forward porting the old algorithm, with an option to turn it on/off.

ZXByteman commented 3 years ago

Old Russian broadcasts seems to suffer from this issue when multiple pages are transmitted with the same subpage code. It would be nice to have such feature. image

ali1234 commented 2 years ago

This is also a problem when pages are updated during a broadcast, such as breaking news updates.