add function when you download video you can watch video and it start download form 0 . so you don't have to wait for the complete download.

Would this be better in the support and suggestions section, with a "Add a preview / stream option" title?
And it was already suggested on another thread, if memory serves me. Just saying ;)

Anyway, there're many options to do it, so one could get the torrent with a preview-capable solution and then just add it (the torrent) to Tixati. Of course built-in would be better, but sequential download is not the best option for torrenting.