annotations_export

[andrbru]

I started working on exporting the EDF Annotations, and probably found some errors there as well.

The first is simple -- if there are no standard channels, an if-statement skips the whole signal writing method, so a file with only annotation signals cannot be exported. I think its better to allow such files, since even official specs mention EDF files with only annotations in the introduction.

Additionaly, it seems there is something wrong with saving of the TALs. I tryed to create files using this library and my results were on the one hand readable with the library itself, but on the other hand displayed as "Annotations are not EDF+" in Polyman.

[andrbru]

I went though the code and tried to understand it. I think the saving method for EDF Annotations signals saves one TAL per AnnoSignal per datarecord, or at least writes it's "annotation index" regardles if there's any annotation message (correct me if i got it wrong). But according to the EDF+ specs, it's allowed to save an arbitrary amount of TALs in one AnnoSignal into one datarecord. Meanwhile the compulsory time index specifying the time of the start of a datarecord can be written only once per datarecord, in the first TAL of the first AnnoSignal.