screensizes in widescreen

[Vman94]

I have a file encoding in MP4 and WMV format at 720 X 408
i am looking to encode the same file in FLV and MPG formats.

the filesizes i used before were 384 X 288 for FLV and 320 X 240 for MPG. Obviously both were not in widescreen at this point. ANy suggestion on sizes for those two in widescreen? keep in mind they obviously want those two filetypes smaller or i would just encode everything in 720 X 408.

any help would be appreciated.

[TheSkiller]

For FLV 384x216 would be an option, but to have roughly the same amout of total pixels (384*288 = 110592) you could use something like 448x252. The problem is just that 252 isn't mod16, but mod16 resolutions for 16:9 at this small size hardly exist.

For the 320 MPEG ones you could use 320x180. To keep the amout of total pixels about the same use 384x216.

[Vman94]

is the 720 X 408 the wrong filesize then for widescreen? should i change that?

[TheSkiller]

Well, 720x408 is a pretty weird size.
Whether it is "correct" or not depends on where that material originates from.
If it's from a DVD or DV tape then it's actually slightly wrong to resize to 720x408 (720x394 would be correct in terms of aspect ratio in that case).

[mike20021969]

Could someone explain widescreen dimensions...

Normally, for widescreen, I would choose something like:
512x288, 640x360, 704x396 or 1280x720 (these are 16:9 or 1.78:1).

Yet, I see lots of other dimensions floating about such as 720x408 (1.76:1) or 720x396 (1.82:1). Although widescreen, these aren't exactly 16x9.

So, what is 'correct'?

[Keiyakusha]

there is no correct, do what is more correct for you. 720x408 is a mod8 resolution closest to 16x9 (also probably without modifying width). 720x396 doesn't looks right, probably it should be 704x396. When widescreen is not exactly 16x9 - this is pretty common, yes. The same you can tell about 848x480 or 864x480. Probably this is because there is not much variety of exact 16x9 resoltions. If you want it to be as exact as possible - anamorphic resolution is what you need.

[yetanotherid]

is the 720 X 408 the wrong filesize then for widescreen? should i change that?

There's no "correct" size for video.

Assuming the aspect ratio of the original video is correct (the image isn't distorted or stretched or squashed in any way) then you'd just want to reduce the width and height by the same percentage (50% for example).
It's generally better (and many conversion programs don't give you a choice) to produce a video with a width and height that are multiples of 16 (mod16). That's why video is usually 720x400 or 704x352 etc. Usually when resizing video the new video's mod16 dimensions give you a video with a slightly different aspect ratio to the original (the video is stretched or squished a little to fit the new dimensions). Often it's not enough to notice, but if you want the output aspect ratio to match the original aspect ratio as closely as possible, sometimes you have to trim a few pixels off the sides or the top or bottom of the original video before you resize it.

Could someone explain widescreen dimensions...

Normally, for widescreen, I would choose something like:
512x288, 640x360, 704x396 or 1280x720 (these are 16:9 or 1.78:1).

Yet, I see lots of other dimensions floating about such as 720x408 (1.76:1) or 720x396 (1.82:1). Although widescreen, these aren't exactly 16x9.

So, what is 'correct'?

Nothing is correct. The dimensions you referred to are, as you said, 1.78:1
However there are other display aspect ratios commonly used such as 2.35 or 2.4 etc. Using DVDs as an example, a video with a 2.35 aspect ratio would have black bars added to the top and bottom so the whole picture, including the black bars, has a 1.78 aspect ratio. Most people, when converting those DVDs, would crop off the black bars first. That's when the output aspect ratio might end up being something like 704x288. Your new "cropped" video should look exactly the same as the original DVD, only the black bars aren't encoded as part of the video.

Most playback devices will play back video of any shape and simply enlarge it till the width or height fills the screen. If the video happens to be of the same dimensions as the screen it will fill it completely, if not there will probably be empty screen space (black bars) top and bottom etc. So when you resize video you're not aiming for an aspect ratio that matches a particular screen size or standard aspect ratio, you're aiming for a new size which has an aspect ratio (width and height) that's in proportion to the original.

In the case of your 720x408 video the height (408) is not mod16. Whether you can resize it down to non mod16 dimensions will probably depend on the conversion program you're using. Assuming you can't 384x218 is a pretty close re-size but 218 isn't mod16 either. Therefore you might crop 8 pixels from the top and bottom of your original video before resizing it..... 720x392..... and after resizing down to 384x208 (not 218) you'll have of course lost a few pixels, but the smaller image will still have the same picture aspect ratio (as opposed to display aspect ratio or dimensions) as the original.

The alternative if you want to resize without distorting the picture would be to use a program which will add black bars to the output if necessary... it'd kind of be the opposite to cropping first. For instance you could take a 2.35 aspect ratio video and encode to 1.78 dimensions and the program would add the black bars required for the whole picture to fill a 1.78 aspect ratio screen.

I hope all of that makes sense.

[yetanotherid]

I should add.... everything in my last post assumed you're converting to a video which uses square pixels. The alternative is to use non square pixels (as DVDs do) in order to keep mod16 pixel dimensions but at the same time to have a video with completely different display dimensions. An MPEG encoder, if converting for DVD playback, would probably choose the non-square pixels used by DVDs by default... it'd probably also force you to stick to standard DVD/CD video dimensions and then add any black bars if required... but for most other formats, square pixels are more the "norm".
Anamorphic encoding is really a whole other topic, but it's possible to use the closest mod16 pixel resolution while adjusting the shape of the pixels in order not to distort the video after it's been resized, however whether you'd do so depends on the format you're converting to and the kind of devices you'd be using to play the video. If in doubt, stick to square pixels.