progressive encoding for a 30p DVD? at
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Old October 14th, 2005, 10:00 AM   #1
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progressive encoding for a 30p DVD?

I know a progressive scan DVD player and TV will take advantage of a 24p DVD but will it have the same benefits for a 30p/25p DVD?
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Old October 14th, 2005, 10:20 PM   #2
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Possibly, depends on the audience's manufacturer and their MPEG-2 decoder chips, if it first decodes into interlace then converts to progressive, it's not likely the result would be HQ. but if the player is true 100% progressive (the HD up-converter DVD always are.) they will take advantage.
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Old October 16th, 2005, 02:43 AM   #3
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From what I understand, the progressive mode setting on DVD players are really only for 24p originated source footage. Supposedly, it removes the pull down before sending the image to the TV via the component interface, so your digital (HD or ED) tv displays a higher quality image.

Most digital TVs can now remove pulldown as well, but only when receiving signal through the analog inputs (composite and s-video). For example, my Sony HD set has three settings: interlaced, progressive and cinemotion. If I'm watching regular broadcast tv, there is a noticable difference in each setting. However, if I'm watching a DVD (DVD setting to Progressive via component output), those options disappear (same if I'm watch HD digital cable), but if I set the DVD player to output interlaced, those options come back on the TV.

For authoring a non 24p progressive DVD, author at 50i/60i; you will still achieve the progressive effect as 25p/30p because each field is displaying the same frame. Your resolution isn't reduced from your source footage because it's progressive to begin with (assuming you edited and rendered all effects on a 25p/30p timeline). When showing your footage from the DVD, make sure the player's settings are set to interlaced and your TV is set to interlaced.

I guess in this case, two interlaces make a progressive. (how much more video-geeky can I be?).

I found all this out because of some videos I shot for a tradeshow a couple of years ago. I shot and edited everything in 60i (as I usually do), and lo-and-behold the client used 42" EDTV LCDs to show the videos. Just for having a trained eye for video flaws, I was a little too aware of the "tearing" effect on fast moving interlaced areas (the client didn't notice) and I originally thought it was the MPEG-2 encoder's fault. After giving this some thought, flat-panels are inherently progressive, so I deinterlaced the whole video to 30p and reauthored the DVD, previewed it the next day on their panels and viola! Nice progressive footage with no "tearing".

Last edited by Xander Christ; October 16th, 2005 at 03:16 AM.
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Old October 16th, 2005, 03:06 AM   #4
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Hi Thomas,

Most of current DVD players in the market do not support HDTV. You you mention 24p, 30p and so on, I assume you're trying to get HD content out onto your TV?

Remember that every DVD manufacturer will always try to claim that their DVD player is 'truly progressive scan', i.e. it implements true progressive DVD decoding. The truth is, when film makers encode DVDs, they already compromise this. I don't think that when DVDs are created, they are truly non-interlaced. The interlace is already introduced at the DVD encoding stage.

So by the time you're popping that DVD into your DVD player, chances are whether it implements a progressive scan properly will matter little.

I'm not sure if I'm answering your question. Guess what I'm trying to say is that in your conventional DVD player - the ability to have progressive encoding, etc. matters very little in the final TV output quality.

Best Regards,
Gary Hendricks
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Old October 16th, 2005, 04:04 AM   #5
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While 24p and 30p are not part of the official NTSC specs, filmmakers have indeed found away around them. With 60i, you can get 24p using 3:2 pulldown, or 30p by recording the same image to both fields to yield a true progressive image. This is independent of the monitor's native resolution.

Today's DVD players are capable of removing the 3:2 pulldown to eliminate interlace artifacts on progressive scan displays (primarily EDTV and HDTV LCD and plasma flat panels). However, how does the DVD player know if the footage being played is 24p or 30p? I know that some DVD players and ED/HDTVs make assumptions that if the user sets the player up for "progressive" output, it automatically assumes it's 3:2 pulldown. Some players and displays watch the stream and make on-the-fly guesses as to which fields to remove (Philips is notorious for doing this this) which can lead to some glitches.

When HDTV-based DVDs becomes the norm, this 50i/60i thing becomes irrelavent because the MPEG-2 stream will tell the display what resolution and frame rate to show the movie (that's why HDTV's have DVI/HDMI and HDCP ports... 100% pure digital transmission!!!).

So, ultimately, Gary, you are correct in that the resulting output will always be interlaced, but if your source footage is true 30p, and you author at 60i, your final output will be "true" 30p on a 60i display.
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