Alley in Pisa, Italy

by Lars Kotthoff

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Working on some scholastic sports mutlimedia pieces, finished project to go on DVD. Last season (the one the got all the parents stoked) I didn't do conversions, thinking they would just go on computers. Well, some go on TV too. NO complaints, which is a good thing, but in the pursuit of awesomeness I'd like to have a TV and computer option.

So, does anyone remember/know the math to squish the pixels?

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2 Answers 2

If you are trying to encode everything yourself, then I think you need to convert to the YIQ format. This is very similar to YUV, both of which are forms of YCC encoding. I would be surprised if you need to write the encoding algorithm yourself...is there some reason you can't just use an existing program that can generate an NTSC compatible DVD for you?

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The YIQ encoding is the least of the challenges. Most of the content on a DVD is in VOB files. The content in the VOB files is MPEG encoded, which is decidedly non-trivial. While it's obviously possible to write your own MPEG encoder, I'd be surprised if even a superb coder could do it in less than a few months of full-time work. –  Jerry Coffin Mar 28 '11 at 23:11
    
@JerryCoffin: Yeah, there are a lot of other concerns involved in encoding video. YCC encoding, MPEG conversion, Audio interleaving, packing into VOB, layout of the disk content, creation of the necessary menus and DVD scripting, etc. Thats a LOT of work... –  jrista Mar 28 '11 at 23:17
    
Okay, you guys are over my head on this one. I'm not trying to write a DVD encoder. Not interested. I'm using DVD Studio Pro and it seems to do the job. What I'm looking for is the math to punch into Photoshop to re-size the images so they look right on NTSC. In other words stretching them so when they hit the screen the resulting squish makes them look correct. –  Rob Clement Apr 10 '11 at 17:50
    
Ah! Sorry, totally misunderstood your question. I think all you really need to do, in that case, is resize the image for NTSC resolution (which is pretty darn low...480 lines), then crop to 4:3 ratio. If your taking your own photos from a 3:2 ratio camera, then your only option is to crop...any other scaling will skew the image. –  jrista Apr 14 '11 at 4:21

NTSC pixel aspect ratio is 9:10.

So you need to crop images to the right image aspect-ratio considering the pixel aspect-ratio. Which is crop to 4:3 ratio and then resize to 720x480 without constraining proportions.

Once the pixel aspect-ratio is taken into account this gives a 4:3 image that fills an NTSC screen.

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