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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 17th Aug 2004, 10:54 am   #1
ppppenguin
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Default The AURORA standards converter / Moving objects theory

Darryl's AURORA standards converter arrived here this morning. I have not actually bought it (yet!). This one is for review and evaluation in a European environment. After I've done my bit, the plan is for it to go to David Boynes to try on a wide variety of sets. If anyone else wants to try it, especially on the mechanical standards, please let me know.

I intend to bring it to Harpenden on 5th September where I'll do a simple demonstration. If anyone brings along a set, mechanical or electronic, we can have a go at hooking it up.

I will do a full review for the BVWS Bulletin and post a summary in the forum. I will only be able to test 405 myself. If anyone can offer to test it on other standards, especially Baird 30 line and French 819 line, I will be very pleased to include those results in the review with full acknowledgement of the contribution.

See Darryl's web page for more details:

http://converter.home.comcast.net/

My first impression is that it's tiny! 4.5 " x 3 " x 1.5 " It certainly works OK, delivering a good 405 line picture into a video monitor.

Last edited by Dave Moll; 4th Jun 2007 at 2:57 pm. Reason: update URL link
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Old 17th Aug 2004, 11:29 am   #2
oldeurope
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Default Re: The AURORA standards converter

Hi Jeffrey,
nice to hear that Darryl's converter arrived in Europe.

I am interested how it handles fast moving things
going up and down, left and right.

Are you able to make a 405 demo tape?

Kind regards

Darius
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Old 18th Aug 2004, 2:08 pm   #3
ppppenguin
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Default Re: The AURORA standards converter

MOVING OBJECTS

This note is from theory rather than experiment.

Where the input field rate and interlace is the same as the output there should be no motion effects at all. For example 625/50/2:1 to 405/50/2:1. This is based on the assumption that there is no attempt to interpolate between spatially adjacent lines on odd and even fields. This would give excellent still pictures but hopeless movement effects.

Where the field rate is the related but interlace differs I'm not sure what will happen. There may be " field splitting " motion effects. For example 625/50/2:1 to 240/25/1:1

Where the field rate differs there will be motion judder effects as fields are dropped or repeated. 625/50/2:1 to 525/60/2:1

Where the field rates are radically different, as for mechanical standards, there may be artifacts but I doubt that they will matter!

On the USA version with 525/60/2:1 input there are special features to take advantage of film material telecine'd with 3:2 pulldown. These features will improve the conversion of film originated material.

I'm sure that Darryl may wish to correct any errors I have made.

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Old 19th Aug 2004, 1:34 pm   #4
tubesrule
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Default Re: The AURORA standards converter

This is absolutely correct Jeff. When converting between two interlaced standards of the same frame rate, all processing is done on a field basis to avoid introducing any motion artifacts. While it is better for image quality to process as a progressive image, this would cause severe motion artifacts on moving objects. There are very high end processes which convert the image to progressive, and then do motion estimation on objects that appear to be moving in the frame, but this is extremely costly to do, and can be error prone.

When converting between interlaced standards of different frame rates, frames need to be added or dropped to make up the difference in rates. Simple duplication or dropping will give the desired frame rate, but because of the nature of interlaced video, will cause motion judder. This is because the fields will be played back out of temporal order. The easiest way to improve this situation is to interpolate between the frames being added or dropped to create a frame that is temporally in order. This greatly reduces the judder at the cost of softening the image on these interpolated frames. The bottom line is there is no perfect way to convert interlaced video between frame rates, and every method is a compromise. It comes down to how good you want it to look, and how much effort you want to put in.

Darryl
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Old 19th Aug 2004, 2:29 pm   #5
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Default Re: The AURORA standards converter

Hi All

Just curiuos...when converting 625 to 405 how many lines are used for the interpolation?.

The DOMINO uses two lines from the input standard (same field) to make one output line.
Using frame or line stores this was the simplest way to do a reasonable conversion.

and just because I havnt heard it mentioned for a while I will say the magic word...XILINX ...there Jeff that should keep you happy

All the best
Malcolm
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Old 19th Aug 2004, 8:33 pm   #6
tubesrule
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Default Re: The AURORA standards converter

Hi Malcolm,
The firmware Jeff presently has uses 2 line interpolation. I am changing the firmware now to increase the video bandwidth, and since it looks like I have the room with everything now in, I am going to 3 line interpolation.

BTW, thanks for the Xilinx fix

Take care,
Darryl
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