On interlaced, progressive, video and DVD players
It seems like we are in agreement then that regardless of whether the DVD content was originally shot on film or video, the resulting fields are interlaced. Your only point seems to be that the process of recombining the interlaced fields to produce progressive output (deinterlacing) doesn't lose any information. I see your point, there is no interpolation or scaling or anything else involved. And it should not produce artifacts, if done correctly. That is a very good point. Well taken. It is not directly in disagreement with anything I previously said, since I didn't say anything about whether information was lost or added in the deinterlacing step, only that an extra step was involved. Still, I guess you're right if you mean to say that ouputing the same information in a different way can not really be called "upconverting", since, after all, it is still the same information. And clearly the result will be the same whether the player does the deinterlacing or the display does it. As long as they both perform the deinterlacing correctly the final result should be identical either way.
On the other hand, when the source material was originally 60i, you can't just combine two adjacent interlaced fields since they were taken at different points in time, and would not mesh well if there was rapid movement during that 1/60th of a second. In that case the player really does have to interpolate to fill in the missing alternate lines of information. So, then it would be completely correct to say that in this case the "progressive scan" player really "upconverts"? In the case of 60i video the player has to "fill" the physical space by interpolation. In the case of the 24fps film, the player has to "fill" the temporal space, which is done by repetition, 3:2 cadence. Have I understood you correctly? Thanks again for the explanation.