Output Dimensions
by James Baker
on
May 22, 2008 at 3:44:19 pm
I have some questions about dimensions for broadcast.
Sorry if they have been asked before but I cannot find
any clear answers in the forums.
I have read that if you are showing a widescreen piece of work on DVD it needs to be outputted as 720 x 576 but with the widescreen setting and aspect ratio 1.42?
Is this the same if you are supplying a file to be broadcast
on TV or can it be supplied and broadcast in widescreen dimensions?
Is this standard practice? Does this not significantly reduce
the quality when it is stretched to the widescreen size?
Also in after effects should you scale the widescreen film into
the 4:3 composition so that it has black bars on the top and bottom?
Do these black bars have some special code to distinguish them from
normal pixels. How does the player recognise the widescreen film inside the 4:3 in order to stretch just that area.
What happens if you have the DVD video file set with dimensions
1024 x576?
Will it play normally on a widescreen tv and then be cropped on
a standard one or will standard one squash it?
Also if a DVD video with HD dimensions like 1280 x 720 is played on a SD tv will it fail to play or playback incorrectly?
Re: Output Dimensions by Dave LaRonde on May 22, 2008 at 4:10:07 pm
First, a few questions: if you want to know about delivery for BROADCAST, why on earth do you want to author it for DVD? The video for all standard-definition DVDs is encoded to MPEG2, a lossy format.
Why aren't you going to tape, and why haven't you gotten the broadcaster's delivery specifications? After all, it's not about what YOU want to deliver to them, it's all about what THEY want you to deliver to them. I can't believe that organizations like the BBC or ITV would accept anything on DVD.
Okay, if you shot the only video in existence of the Savior's Second Coming, and it exists ONLY on DVD, they'd probably make allowances.
[James Baker]"I have read that if you are showing a widescreen piece of work on DVD it needs to be outputted as 720 x 576 but with the widescreen setting and aspect ratio 1.42? "
Why don't you just use AE's PAL DV Widescreen comp preset? Then you'll know for sure if your information is correct.
"How does the player recognise the widescreen film inside the 4:3 in order to stretch just that area."
When you author a DVD, you typically have to tell the authoring software that you're making a widescreen DVD. You may also have to tell the software that the video is supposed to be widescreen and not 4x3. How do you do that? Look in your authoring software manual.
"What happens if you have the DVD video file set with dimensions 1024 x576? Will it play normally on a widescreen tv and then be cropped on a standard one or will standard one squash it? "
SD PAL DVD authoring software can't make an MPEG2 file in 1024 x576. It can only make 720x576. It doesn't matter if the picture is 4x3 or 16x9, it's still 720x576. But by telling the software that the video is supposed to be widescreen, the DVD will play in the proper pixel aspect ratio for widescreen and it will automatically add the letterboxing for proper playback on 4x3 TV sets.
"Also if a DVD video with HD dimensions like 1280 x 720 is played on a SD tv will it fail to play or playback incorrectly? "
As stated earlier, you can't make DVD video with HD dimensions like 1280 x 720. It HAS to be 720x576. Your authoring software may be able to scale the HD video before it in encodes it to MPEG2.
Personally, I wouldn't trust authoring software to do that. I'd rather do the scaling in AE, which is very, very good at such things.
Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
Re: Output Dimensions by James Baker on May 23, 2008 at 12:52:40 am
Thanks for your reply. I have another issue which I am unsure about relating to the relevant dimensions to use.
I am under the impression that the square pixel equivalent of 720 is 788 and not 768.
If so why is the preset not 788?
If you are making a composition in after effects to be shown eventually on a non square pixel device like a DVD player should you make it in 788 x 576 so that it is the same real space area as 720 x 576?
Should the same be applied to the equivalent widescreen dimensions which I am led to believe is 1050 x 576 instead of 1024 x 576?
If this is true do you know why these dimensions aren't in the presets?
Re: Output Dimensions by Dave LaRonde on May 23, 2008 at 3:24:43 pm
Mind you, I work in NTSC and not PAL, but if there's a standard-definition PAL square-pixel comp preset in AE, you can use it with confidence. It will be right, and you don't have to overthink it.
Similarly, if there's an SD PAL Widescreen preset, you can use it with no fear.
If you want to work at a higher and square-pixel resolution for SD PAL Widescreen, you can do so. When you're finished, you can nest your work into an SD PAL Widescreen comp, then use the "scale the layer to fit the comp" preset (command-option-f Mac, ctl-alt-f Win).
The people at Adobe have already thought about these things for you...
Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
