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afterdawn.com > forums > home theater > televisions > frame rate conversion in tvs
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Frame rate conversion in TVs
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tezmen
Newbie
_ 		30. January 2006 @ 05:52 _ Link to this message    Send private message to this user   
Do TV's preserve the frame rate of a video source while displaying the video or do they convert them to a certain frame rate?
To clarify the question consider this example:
Let us say you have a 720p@24fps source and you connect it to a TV which you know is able to accept 720p@24fps. Will the TV display the video at 24fps or convert it to its default frame rate?
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diabolos
Suspended due to non-functional email address
_ 		30. January 2006 @ 14:12 _ Link to this message    Send private message to this user   
Quote:
Will the TV display the video at 24fps or convert it to its default frame rate?
Its a complicated yet easy answer. It depends on the type of display in question.
It is my understanding that...

A CRT (based on the ATSC spec) will display a 720p@24fps signal in a 720p@60fps interlaced fashion at 60 frames per second. Meaning that it will upconvert to 720p@60fps.

A Fixed Pixel display (Plasma, LCD, DLP, and LCoS) will upconvert the 720p@24fps to it's native resolution and frame rate.

In both cases a "Good" video proccessor will recognize that the stream was originaly created from film and take the necessary steps to start 3:2 pulldown decoding. Then the display will either display the video stream using reverse 3:2 pulldown proccessing if the display is a CRT or if the tv is a Fixed Pixel Display it will use reverse 3:2 pulldown then deinterlace the fields.

For example:

CRT:

720p@24fps -> 3:2 pulldown -> CRT -> reverse 3:2 pulldown -> Scale to 1280x720 -> 720p@60fps

Technically a CRT can support just about any resolution at 60fps since it isn't a Fixed Resolution Display... That is just one example of many possible resolutions

Fixed Pixel Display:

720p@24fps -> 3:2 pulldown -> FPD -> reverse 3:2 pulldown -> Deinterlace -> Scale to "Native Resolution" (1280x768, 1366x768, or 1920x1080) -> (either) 720p@60fps or 1080p@60fps

I could be wrong about the end frame rates but the method is good.

For more explination:

3:2 Pulldown and Deinterlacing:
http://www.theprojectorpros.com/learn.php?s=learn&p=theater_pulld...

Scaling:
http://www.theprojectorpros.com/learn.php?s=learn&p=theater_scalers

I love technical questions,
Ced
[ + quote]
My Afterdawn page:
http://my.afterdawn.com/diabolos/

This message has been edited since posting. Last time this message was edited on 1. February 2006 @ 18:52
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