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Old September 17th, 2007, 07:49 PM   #1
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HDV 1080i to DVD letterboxing...

Hi folks,

I'm about to render a project for DVD which was shot on a Z1 in 16:9 HDV 1080i and I've edited it in Vegas in HDV 1080i. (I'll be delivering it in HD too, a bit later.)

But my question is: should I set the rendering Aspect ratio as 16:9 display or 4:3? The footage is in 16:9 obviously but I have a hazy idea that it's actually DVD players which stretch a 4:3 image to the widescreen format and need some clarification about this...

Also, whenever I output as Widescreen 16:9 I get very narrow black vertical letterboxes on the rendered file, is this just normal or am I doing something wrong?

Many thanks,

Baldwin
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Old September 19th, 2007, 06:52 AM   #2
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Quote:
Originally Posted by Baldwin Li View Post
But my question is: should I set the rendering Aspect ratio as 16:9 display or 4:3? The footage is in 16:9 obviously but I have a hazy idea that it's actually DVD players which stretch a 4:3 image to the widescreen format and need some clarification about this...
You should render as DV Widescreen to maintain the 16:9 aspect ratio that you shot the footage in. DVD players will correctly recognize it and it will display correctly on widescreen TV's and letterbox on standard TV's. You do not want to render as 4:3 because this will burn in the letterbox bars and even on a widescreen TV it will be letterboxed and stretch out of proportion.

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Also, whenever I output as Widescreen 16:9 I get very narrow black vertical letterboxes on the rendered file, is this just normal or am I doing something wrong?
What is your project set to? HDV or DV Widescreen? The slight letterboxing you see sounds to me like HDV footage on a DV Widescreen timeline. This is because DV Widescreen is not exactly the same aspect as HDV Widescreen.

The way to fix this is to always work in with an HDV project even if your final output is DV Widescreen. Then when you render, check the rendering option: Stretch video to fill output frame size (do not letterbox). You can't do this from a DV Widescreen timeline because the timeline is already letterboxing it. So it has to be rendered from an HDV timeline.

~jr
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Old September 19th, 2007, 04:01 PM   #3
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Many thanks for the message, john, i just needed to tick that box "Stretch video to fill output frame size (do not letterbox)" and gone are those little letterboxes and people now dont look that tiny bit thinner.

Cheers,

baldwin
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Old September 20th, 2007, 12:09 AM   #4
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Just so I understand... Is it advisable to always tick the "Stretch video to fill output frame size (do not letterbox)" when downsampling a 1080i project to Standard DVD? I understand that we need to work in an HDV project and render to a Widescreen DV format but the tick box is a new one for me.

Thanks,

Marc
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Old September 20th, 2007, 07:03 AM   #5
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Just so I understand... Is it advisable to always tick the "Stretch video to fill output frame size (do not letterbox)" when downsampling a 1080i project to Standard DVD?
Yes, because the 16:9 aspect ratios are slightly different. HDV has a true 16:9 ratio while DV Widescreen is close to 16:9 but not quite.

If you want to do the math:

HDV is 1440x1080 at 1.3333 Pixel Aspect Ratio (1440 * 1.3333 = ~1920x1080)

DV Widescreen is 720x480 at 1.2121 Pixel Aspect Ratio (720 * 1.2121 = ~873x480)

If you compare these to the 16:9 ratio: 1920 / 16 = 120 and 1080 / 9 = 120. A perfect 16:9 ratio. However 873 / 16 = 54.5 and 480 / 9 = 53.5 so DV Widescreen is slightly wider horizontally that 16:9 which causes HDV to leave small black bars if you don't stretch it.

~jr
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Old September 20th, 2007, 08:09 AM   #6
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Hi,

John, the aspect ratio explanation was excellent.

However, I have noticed that leaving these small black bars at both sides just isn't a problem on most display systems.

These narrow black edges shows on a computer screen playing the DVD (so what?), but on a 16:9 monitor they practically disappear. This is due to the slight overscan suprisingly even these LCD TV's have. 16:9 CRT's definitively make these edges to disappear.

To guarantee the output quality, I never myself selected the tick box (Stretch video to...). Any line (and screen size) interpolation/stretching is not going to at least improve the finaly quality, on the contrary. Do you agree on this John? You probably have more experience than I have. I neved did an A/B comparison, just did some theoretical thinking.... that sometimes can mislead even me ;)

Christian
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Old September 20th, 2007, 07:08 PM   #7
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Yes I agree that any stretching is going to cause some hit to quality. But you are already converting 1920x1080 to 873x480 so you have 5x the resolution to start with and I'm not sure if the degradation would be perceptible. It does, however, make everyone a little heavier looking because it only stretches horizontally. ;-) I also agree that the black bars all but disappear on TV.

An alternate way would be to work in a DV Widescreen timeline and add a Pan/Crop and Match Output Aspect to the HDV footage. This is better because it would not stretch the footage at all but rather crop to size.

~jr
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Old September 20th, 2007, 11:44 PM   #8
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Thanks for the detailed explanation John.
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Old September 21st, 2007, 07:11 AM   #9
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The alternative, ratio preserving approach would be to nest the whole project inside another and use the track motion tool to slightly zoom in. I've got a feeling this would only work in progressive though, and you need to make sure you have blend switched on in the deinterlacing mode.
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Old September 25th, 2007, 11:04 AM   #10
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Originally Posted by Christian de Godzinsky View Post
These narrow black edges shows on a computer screen playing the DVD (so what?), but on a 16:9 monitor they practically disappear. This is due to the slight overscan suprisingly even these LCD TV's have. 16:9 CRT's definitively make these edges to disappear.
Many 1080p TVs can be set up for zero overscan for 1080p sources (dot-by dot mode). I am not sure does zero overscan work for 480i/p sources as well. I don't have a 1080p panel, my Panasonic plasma has 2%-5% overscan depending on a source.
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Old September 25th, 2007, 12:50 PM   #11
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Hi Michael,

That is good to hear, I never understood why fully digital TV's fed with digital (HDV or DVD) inputs (using LDC screend) have this overscan. I am glad to hear that the newer sets are capable of dot-to-dot display. That is GOOD news :) Never stumbled over one yet. My guess is that 99,9% of the currently installed LDC TV's are overscanning... Thank's for the info.

Christian
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