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Sony Vegas says NTSC=655×480 (Correct) then why WMP and other say 640×480
When converted to square pixels NTSC’s 720×480 should be 640×480 but only after removing 8 pixels from each side (704×480) as TVs do, so Sony Vegas says: hey! I gotta render a NTSC image as 655×480 to keep the correct image ratio.
So, a file taken directly from a NTSC DVD, renaming a VOB to MPG or using Vegas’ FILE > IMPORT > DVD Camcorder Disc for example, will be displayed in Vegas as a 655×480 image but the same file opened in Windows Media Player and others will be displayed as a 640×480 image, making things look thinner.
Why?
Is my information right?
If Vegas is right why doesn’t WMP use the correct pixel ratio?
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1 Reply
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By convention, an analog TV would always show you a 4:3 section of the picture. It would also mask the left and right edges of the picture which would vary in raggedness depending on how good all the tubes were in your TV. And they were never all that good.
Remember, this standard developed before there was such a thing as solid state electronics. TV’s had to be warmed up for a minute or two before the picture was stable, and then pictures would vary grossly from one TV to another. So there was a lot of room for slop built into the way TVs would display the picture.
Now, as to why WMP would display your 720×480 image as 640×480 while Vegas might display it as 655×480…most programs tend to try to display SD video in a 4:3 ratio because that’s what the designers think they’re supposed to do and it’s what the customer expects. Vegas, on the other hand, just sticks to the math and interprets sample rates the way they are supposed to be interpreted. Vegas has it’s roots in audio, after all, and DV is just a digital sampling of an analog standard.
In the end, the digital SD image for DV and for SD DVDs is still 720×480, no matter how the player interprets it.
Rob Mack
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