Brian Butterworth wrote:
If you are going to be pedantic, at least be right! UKTV (and all in Europe) is 25 frames a second
> > I suspect yuou don't understand what "interlaced" means.
I think I detect an impending semantic argument, so let me try and avoid it. You're (I think) defining a frame to be the combination of as many sequential scans of an image (fields) as are required to build up a full-resolution two-dimensional picture. Two fields per frame, in the present case.
Let me expand slightly: fields are often bundled together and called frames for broadcast purposes, although not necessarily in such a way that they form a combined image (eg two fields may be placed one above the other to form a frame for some MPEG treatments of interlaced material). Because of this, yes, you can describe 50 fields-per-second television as "25 frames-per-second". I would like to argue, however, that it is misleading to characterise an interlaced television system in terms of its frame rate.
Why? Because each field comes from a different point in time, and combining them together leads to spatial ("combing") and temporal ("judder") artefacts. (There are exceptions to this rule, eg when each frame of a film is broadcast as two successive fields - in this case simple recombination of the fields does not necessarily result in these artefacts.)
S - Sent via the backstage.bbc.co.uk discussion group. To unsubscribe, please visit http://backstage.bbc.co.uk/archives/2005/01/mailing_list.html. Unofficial list archive: http://www.mail-archive.com/backstage@lists.bbc.co.uk/
