@paulb_nl
the moment the FIRST line from the 2nd field is coming in (and hence is available for ANY deinterlacing alorithm other than a single-field doubling like BOB) the 1st field has already been output first to last line by the source. So, comparing the output of the processor to the output of the source, you're already lagging behing a frame by this moment.As you are comparing the current field to previous field there is no frame of lag.
@ASDR
same as above. the oldest field you're referencing with is always your base. If you're using any kind of motion adaptive deinterlacing, which retains information of the previous frame for creating the current one, your output will always lag at least by the time one field needs to be written to the buffer. Hence ANY information from that field, that is used for the current frame output, is at least 1/60s old by the time you start using it.For the above to work we only need to buffer fields, which does not introduce any lag, and refer to past fields, which also does not introduce any lag.
If you can't believe it, draw two timelines, one for the odd, one for the even fields and mark down the point the information is available for processing. That's the earliest point in time a fresh frame can be output.
pure weaving as in film mode deinterlacing isn't interesting for gaming content. And for movies you need more than a single field buffer because of the cadence breaks.Weaving the previous two fields together, retaining full resolution but creating combing artifacts with motion