Dallmeier electronic

Dallmeier recorders now with PDA connectivity


 

Nomenclature

Dallmeier HD High Definition

HDTV broadcast systems are defined by:

  • Number of lines (frame size):
    e.g. 1280 x 720 or 1920 x 1080, combined with i or p, depending on the 

  • Scanning system:
    i = interlaced (image build-up by two separated, consecutive fields)
    or
    p = progressive scan (image build-up with progressive scan method)

  • Frame rate
    is defined by the number of frames per second (fps): 25 or 30 frames (sometimes indicated as 50 or 60 fields respectively)

1) Number of lines

The figures 720 or 1080 respectively each indicate the number of vertical pixels; or, in other words, the number of horizontal lines.

3) Frame rate

Since the indications fps always refers to “frames per second”, the figure after the forward slash incdicates the number of frames per second. Sometimes there are indications without a slash, for instance 1080i50. In this case the figure 50 does not represent for the number of full frames but rather the number of half frames (i.e. 1080i50 = 1080i/25).

Why is that number lower with interlaced than with progressive scan?

Example: 1080i/25 or 1080p/50 respectively

With the interlaced scan two fields are subsequently transmitted. Therefore, within the stipulated time period of one second, a maximum of 50 half frames can be transmitted. This equals 25 full frames.

In contrast, with progressive scan every image is transmitted as a full frame. Hence, a maximum of 50 full frames can be transmitted per second.