If it's on Dave, which is interlaced then it's definately fields! 25 frames per second, 2 fields a frame
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Just had to look up on Wikipedia - fields is relating to interlaced formats, while frames is progressive. My jargon got a bit mixed up yet again...
In interlaced formats, two fields contribute towards one frame. Each field contains (more or less) half the number to scanning lines, for SD that's 288 active lines per field, or HD 540. Interlacing is nothing more than a 2:1 compression scheme, and has been with us since the 1930s. With CRT displays, the tube's persistence couples with human persistence of vision gives the illusion of a full resolution image, because the lines for odd and even fields are, interlaced.
Flat panel displays are intrinsically progressive devices, so in order to display interlaced video, de-interlacing is required, this is where motion and other aretfacts can get introduced if this is not done with care.
When film derived material is shown (or when interlaced footage has been adapted to look like film), field 1 and field 2 are identical (just like progressive at 25 frames per second). Transmission is still interlaced, so when seen on flat panels, the signal has gone from p to i to p again. Unnecessary. This is why the UK HD
DTT channels are encoded such that when the encoders sense f1 and f2 are the same, the transmission changes from 1080i50 to 1080p25.
The holy grail is 1080p50, but of course that's twice the bandwidth. Used increasingly pre transmission within the studio/OB truck for maximum production quality, and for upscalling to 4k
4k/UHD formats only exist in progressive form thank god.
