Just got a 16:9 TV for Christmas and am learning about DVD movies that are “enhanced for 16:9 television”. I understand the concept of allowing the full resolution of the video going to the television, without the black bars, for an improved picture (they look great, BTW). My question is how is the video stored on the DVD? Is the movie squashed horizontally on the disk and sent as is for 16:9 TVs to expand back out? If so, what happens for regular 4:3 TVs? Is the video then squashed vertically and the black bars added by the DVD player, or are every few scan lines thrown out, or what?
There are two kinds of widescreen DVDs.
Anamorphic Widescreen discs have the full widescreen resolution picture stored on the DVD. If the DVD player is in 4x3 mode, it adds the letterboxing and compresses the signal to fit on a 4x3 TV.
Then there are the occasional DVDs that are recorded in 4x3, with the letterboxing as part of the actual video signal. You want to avoid these at all costs, because when you watch them on a 16x9 TV, you have to “zoom” the picture to get it to fit, yielding horrible resolution.
Thanks. So, specifically, what does the DVD player do to compress the signal to fit a 4:3 TV?
And if the Anamorphic DVD has the full vertical resolution (i.e. no black bars) available to a widescreen TV, what about the horizontal resolution? Is that compromised in some way?
Every four lines of vertical resolution is compressed to three lines for the 4x3 TV, yielding a 25% decrease in vertical resolution. It still looks pretty good on a good TV, though.
No, the horizontal resolution remains intact. This is why if you accidentally switch your DVD player to 16x9 mode while hooked up to a 4x3 TV, the anamorphic image will be squished horizontally while appearing normally vertically. Here is an excellent demonstration.
NTSC DVD resolution is 720x480, which is slightly stretched horizontally to account for the fact that pixels on a TV aren’t perfectly square. This also has the effect of increasing horizontal resolution, improving display quality.
A 2.35:1 Anamorphic DVD has actual the video taking up 720x360, with black bars filling out the rest of the 720x480 frame. Given that the “proper” resolution (taking into account, again, non-square pixels) would be 720x272, there has been a 32% increase in vertical resolution.
That’s what I was looking for. Thanks!
Also, that link is something I earlier searched for and could not find. Makes a nice intro for my friends who wonder why I shelled out too much money for a 16:9 TV.