Editing Sampling (signal processing) (section)

=== Video sampling ===
{{More citations needed section|date=June 2007}}
[[Standard-definition television]] (SDTV) uses either 720 by 480 [[pixels]] (US [[NTSC]] 525-line) or 720 by 576 pixels (UK [[PAL]] 625-line) for the visible picture area.

[[High-definition television]] (HDTV) uses [[720p]] (progressive), [[1080i]] (interlaced), and [[1080p]] (progressive, also known as Full-HD).

In [[digital video]], the temporal sampling rate is defined as the [[frame rate]]{{snd}}or rather the [[field rate]]{{snd}}rather than the notional [[pixel clock]]. The image sampling frequency is the repetition rate of the sensor integration period. Since the integration period may be significantly shorter than the time between repetitions, the sampling frequency can be different from the inverse of the sample time:
* 50&nbsp;Hz&nbsp;– [[PAL]] video
* 60 / 1.001&nbsp;Hz ~= 59.94&nbsp;Hz&nbsp;– [[NTSC]] video

Video [[digital-to-analog converter]]s operate in the megahertz range (from ~3&nbsp;MHz for low-quality composite video scalers in early game consoles, to 250&nbsp;MHz or more for the highest-resolution VGA output).

When analog video is converted to [[digital video]], a different sampling process occurs, this time at the pixel frequency, corresponding to a spatial sampling rate along [[scan line]]s. A common pixel sampling rate is:
* 13.5&nbsp;MHz&nbsp;– [[CCIR 601]], [[D1 video]]

Spatial sampling in the other direction is determined by the spacing of scan lines in the [[raster]]. The sampling rates and resolutions in both spatial directions can be measured in units of lines per picture height.

Spatial [[aliasing]] of high-frequency [[luma (video)|luma]] or [[chrominance|chroma]] video components shows up as a [[moiré pattern]].