Questions & Answers:
Scaling, Progressive Scan & Resolution |
| Scaling, Progressive Scan and Resolution FAQ |
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| What is resolution and why is it important? |
The picture your projector or flat screen produces is made up of thousands of pixels. The number of pixels your display is made up of is referred to as its “native resolution”. In general terms the more the better - since this means there are more individual dots available to draw more detailed pictures, which results in sharper detail.
DVD, Sky and other video sources currently use a resolution of 640 x 480 or 720 x 576 horizontal lines (perfect for 42” plasmas and budget to mid-range projectors). Displays with high resolutions (1024 x 768, 1280 x 720 etc) have to scale the image to stretch over this larger number of pixels. The processor will identify shapes in the image and use the extra pixels to smooth off edges or show more detail within the picture. |
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| What is High Definition TV (HDTV)? |
| HDTV is a higher resolution signal than standard TV (higher than current DVD too!). The resolution starts at 480 lines and goes all the way up to 1080 lines!!! At this resolution many displays will still need to scale the image, only this time down to fit its native resolution! It is worth noting that most HDTV broadcasts are already in Progressive Scan format. Unfortunately HDTV is not available in the UK yet L |
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| Is my projector/plasma Progressive Scan? |
All monitors, LCD and plasma screens and projectors must convert any input signal into a non-interlaced image through a process called “deinterlacing”. By definition therefore, any picture you are watching on that display is in “Progressive Scan” format.
DVD Players that have “Progressive Scan” have a similar deinterlacing chip to your display actually built into the DVD player itself. The process is the same but it might be that the DVD player has a better chip than the plasma does. There is also the advantage that when the DVD player is doing the conversion, the signal is in its purest form direct from the DVD disc. |
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Why do video signals need to be converted into Progressive Scan in the first place? |
| In essence, all video starts as a Progressive Scan, or non-interlaced picture. However, CRT televisions require the image to be broken up into two separate “fields” – one made up of all the odd lines of the picture (1,3,5,7…) and the other made up of all the even lines (2,4,6,8…). As a constraint of the technology, for each frame of a picture the CRT television really quickly draws the first field, and then the second one – the human eye puts this flicker together and forms one picture. It is for this reason that videos, DVDs and Sky are all in “interlaced” format which needs “deinterlacing” before it can be shown on a digital display. |
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| So what is a scaler or de-interlacer then??? |
| A very common upgrade for plasma or projector owners is to add a dedicated video processor into the system. This is literally a box that will take one or more video inputs, carry out any and all deinterlacing and/or scaling duties, and output the finished image to your display. Practically all video processors can de-interlace a signal (turn it into progressive scan) and as such feed a Progressive Scan image to the display; many now incorporate a scaling chip too. This means that the processor is able to send a deinterlaced picture of exactly the right horizontal and vertical resolution for your display, hence bypassing the display’s internal scaler, which may be of lower quality. The dedicated processor approach means that all processing is done outside of the source or display hence minimizing electrical interference, and you can seriously improve your picture from Sky, Freeview, Cable etc |
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