Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[raym]

Why is it so hard to get DVD's to display properly on a 16:9 TV? I find myself constantly changing the "Expand Image" aspect ratio setting between disks in order to achieve a fullscreen picture. Sometimes it's too big and over magnified. Other times it's too small and I get black borders top, bottom AND sides. Worse still, when I finally get it right for a given feature, the picture is suddenly so big when I drop back out to the dvd's menu that most of the menu options appear off screen!

I don't have these problems with other video content. Under my Directshow Playback options, I've selected 1.78 : 1 as my aspect ratio and all widescreen content displays fullscreen no problem. Older 4:3 content also displays fullscreen with the acceptable side bars only. Why can't MC scale DVD content for my chosen display type automatically as it appears to do with other videos?

Thanks.

[gpvillamil]

That is probably because there are a lot of DVDs that encode a 16:9 movie within a 4:3 frame, with black boxes top and bottom. MC12 (and standalone DVD players) see this as a 4:3 piece, so they pillarbox it (black bars on the sides) to fit within a 16:9 frame. So you end up with black all around.

With a standalone DVD player, I end up switching back and forth between "full" zoom setting (for 16:9 encoded DVDs, that will fill a 16:9 screen) or the "zoom" setting (for 16:9 letterboxed in 4:3) that will crop out the top and bottom bars.

The problem is not with MC12 - it is with the way the DVD is encoded. I personally find 16:9 letterboxed a disaster, since it reduces the resolution, and most DVD players can adapt 16:9 content to a 4:3 TV by themselves. MC12 is correctly detecting the aspect ration AS SET ON THE DVD - a 16:9 movie encoded as 4:3 will be treated as 4:3.

When it really bugs me, I re-encode the DVD with AutoGK, which detects the "true" aspect ratio of the content and crops out the black bars, ie AutoGK is smart enough to notice that the black bars on top and bottom never change, and hence you are dealing with letterboxed content.

[jmone]

I also find the codec you select makes a big difference.  One of the reasons I use the nVidia Pure Video codec is that it has always got the aspect ratio correct and I leave MC12 in "Source Apect Ratio".  As GPV pointed out you will still get probs with 16:9 content in a 4:3 frame BUT this is normally from 16:9 Clips in a 4:3 Stream (eg DVD, DVB-T etc).  I posted a similar Q yesterday in the main forum - http://yabb.jriver.com/interact/index.php?topic=40656.0 the MC guys are looking at the ability to tag files with the prefered aspect ratio which is a good start.
Thanks
Nathan

[raym]

That is probably because there are a lot of DVDs that encode a 16:9 movie within a 4:3 frame, with black boxes top and bottom. MC12 (and standalone DVD players) see this as a 4:3 piece, so they pillarbox it (black bars on the sides) to fit within a 16:9 frame. So you end up with black all around.
....

Thanks for the replies and I understand that this has more to do with DVD encoding than with MC. But.... the "black all around" happens to me even when viewing a WIDESCREEN DVD like the ones that preserve the orignal theatrical aspect ratio. Example, "Gladiator: Collector's edition". With discs such as these, I need to set MC's "Expand Image" aspect ratio setting to "1.78 : 1" to achieve a FULLSCREEN picture on my 16:9 display. Why do I need to do this for a DVD whos ascpect ratio is designed for a tv with the same saspect ratio?

 

[jmone]

Thanks for the replies and I understand that this has more to do with DVD encoding than with MC. But.... the "black all around" happens to me even when viewing a WIDESCREEN DVD like the ones that preserve the orignal theatrical aspect ratio. Example, "Gladiator: Collector's edition". With discs such as these, I need to set MC's "Expand Image" aspect ratio setting to "1.78 : 1" to achieve a FULLSCREEN picture on my 16:9 display. Why do I need to do this for a DVD whos ascpect ratio is designed for a tv with the same saspect ratio? 

Over the years Hollywood has kept moving to wider and wider formats for film. "My Galidator: Deluxe Collector's Edition" is in so called "16:9 enhanced" which in their words is to "preserve the original 2.35:1 theatrical aspect ratio on a standard TV".  Where your STD TV is a 16:9 set (1.78:1) you get either letterbox or you have to zoom in and loose some of the left and right of the picture.  Of course 2.35:1 aspect ratio material look terrible on a 4:3 (1.33:1) TV and you get more of just a centre strip!

Thanks
Nathan

PS I've never seen a 2.35:1 TV....

[glynor]

@raym -

There are two different types of Widescreen DVDs:  leterboxed and anamorphic.

Letterboxed is where the video file on the disc is 4x3 shaped, with black bars at the top and bottom which are actually part of the video footage stored on the disc. This is good because you don't miss any part of the action from the original footage, but it throws away all of those horizontal lines on wasted black bars, so the resolution of the remaining image is lower.  For a DVD player (or MC) to scale this image up and put it on a Widescreen display, it needs to crop off the black bars.

Anamorphic was a response to the loss of resolution caused by letterboxing.  On anamorphic widescreen DVDs, the image is actually shaped 4x3, but the whole thing is stretched out to fill up that 4x3 image.  There are no black bars in the image on the disc at all.  If you watched an Anamorphic DVD uncorrected, everyone on screen would look very tall and thin.  Since there are no black bars, you aren't wasting any resolution on "empty black space".  You obviously can't watch it like that though, so they added a special Anamorphic flag to the discs which tells the DVD player "heads up, this is stretched all weird so fix it by squishing it back out".  If your TV is widescreen, it doesn't need to add the black bars, it just shows the video as is.  If your TV is 4x3, then it needs to add in the bars.

So that's the difference.  In one situation (Anamorphic), the DVD player needs to add-in the black bars to play the video back on a 4x3 TV, or just squish and send the image with no bars for a Widescreen TV.  No problem, as long as the DVD player knows what kind of TV it's connected to and that it's an Anamorphic disc.  For a letterboxed DVD, the DVD player needs to send the image unaltered to the TV.  The TV then can crop off the black bars, but only if you tell it to.  The problem is that with letterboxed DVDs there is no special flag on the discs saying "hey, I'm widescreen", so the DVD player (in this case MC) can't tell the difference between a letterboxed DVD and an actual 4x3 video DVD.  Letterboxed DVDs look identical to the DVD player to 4x3 DVDs.  Since the player doesn't know it's letterboxed, but it knows you have a widescreen TV, it adds the black bars on the sides of your TV (displays it as 4x3 content).

Make sense now?

Almost all new DVDs of new content are going to be Anamorphic, because it's a much better technology.  However, older content is often just re-purposed from the original captures from film that were used for VHS and LaserDisc (remember those?) distribution.  Since that was before anamorphic content hit the scene, they are often letterboxed, unless they actually re-scan the film (but that's expensive so it only happens if they know it'll be financially worth it).

[jmone]

Sort of...from what I understand (and happy to be corrected  ) the MPEG/DVD Headers contain a whole lot of information about the video stream including stuff like:
- Aspect Ratios: 1:1, 4:3, 16:9, and 2.21:1 (not used in DVDs)
- Frame Rates: 24000/1001 (23.976), 24, 25, 30000/1001 (29.97), 30, 50, 60000/1001 (59.94), 60
- Horizontal and Vertical Size.

OK - during the transfer process from film the studio really only has a couple of options with their original 2.35:1 Aspect Ratio material, firstly they have to select decide how they want the material to be presented (eg full screen, letter box etc):
1) CROP or PAN/SCAN: cut a "4:3 or 16:9 center" from the original 2.35:1 frame (eg lose content on the left & right of the orginal frame) OR
2) LETTERBOX: ADD a black matt (eg top bottom) to add the extra horizontal height reducing the aspect ratio to either 4:3 or 16:9 fame

In addition the transfer process will need to convert to the TV Standard they want (say 720x576/25, 720x480/29.97, 1920x1080i/50 etc).

All of the above is in the spec so that the CE equipment knows what the resolution, framerate, and aspect ratio is so they can be displayed properly.

ANAMORPHIC video works on a completely different principle and has been around for ages - it uses the concept of non square pixels.  I've got a ton of home video recorded in anamorphic DV which displays as 16:9 wide screen when I play it back, yet the resolution of the actual video is PAL 720x576 which is natively a 4:3 Aspect Ratio.  For those that remember using Film Projectors it was like swapping the Cinemascope Lens for the normal one to get the "extra screen width" from the same film stock.  With video, the "trick" used is that during recording every pixel stores a distorted 9:16 image (all tall and skinny) and the video header is set to a 16:9 aspect ratio for playback.  The result is a widescreen image from a 4:3 video frame as each of the pixels effectively becomes 16:9.

In the brave new HD world there "should" be no need to anamorphic style treatment as 1920x1080 and 1280x720 are native 16:9 with square pixels but we do see standards like HDV using specs like 1440/1080 which is a native 4:3 ratio using the same principles to show you a 16:9 widescreen output without recording all the "full" horizontal resolution (save space!)

Nathan

Edit: Back to the problem for RAYM - He has a 16:9 screen and is watching a video transfer from 2.35:1 film stock where letterboxed it to 16:9 (there only other choice being to have done a CROP or PAN/SCAN).  RAYM can effectively get the same CROP effect by zooming in.  Many would argue that the studio is being slack and just saving products costs as there is no 2.35:1 aspect TV's on the market so why not use PAN/SCAN to create a "fullscreen" 16:9 transfer.

What really gets me going is transfers made for 4:3 transfer which then has 16:9 content embedded in it - you got both Letterbox and Pillarbox (a complete black frame with your video in a box in the middle)!  I've seen a lot of this on "Various Artist" Music DVD's which has a mix of 4:3 and 16:9 clips but they have authored the entire disk as 4:3!  Interestingly some DVD creation packages (even Nero Vision) lets you create a single DVD with multiple aspect ratio changes between “titles” on the disk.

[raym]

Thanks again guys.

Make sense now?

Glynor. Yeah I think so. At the end of the day it seems I need to continue to zoom in or out as necessary in order to get a fullscreen picture depending on the DVD in question and there's no way MC can do this for me automatically. Is that about right?

Cheers.

[jmone]

Thanks again guys.

Glynor. Yeah I think so. At the end of the day it seems I need to continue to zoom in or out as necessary in order to get a fullscreen picture depending on the DVD in question and there's no way MC can do this for me automatically. Is that about right?

Cheers.

Yup - zoom in to remove the black bars top and bottom at the expense of losing some of the picture on the left and right.  FYI Some TV's let you do this from their remote control including various compromises from zooming and stretching the image. 

[glynor]

Sort of...from what I understand (and happy to be corrected  ) the MPEG/DVD Headers contain a whole lot of information about the video stream including stuff like:
- Aspect Ratios: 1:1, 4:3, 16:9, and 2.21:1 (not used in DVDs)
- Frame Rates: 24000/1001 (23.976), 24, 25, 30000/1001 (29.97), 30, 50, 60000/1001 (59.94), 60
- Horizontal and Vertical Size.

In the brave new HD world there "should" be no need to anamorphic style treatment as 1920x1080 and 1280x720 are native 16:9 with square pixels but we do see standards like HDV using specs like 1440/1080 which is a native 4:3 ratio using the same principles to show you a 16:9 widescreen output without recording all the "full" horizontal resolution (save space!)

You're mostly right (and what I said was essentially the same thing but I simplified it by ignoring PAL and odd aspect ratios and whatnot).  There are actually a LOT more aspect ratios out there than just 1.33:1, 1.78:1, and 2.39:1.

One thing I think is different (and I too could be wrong) is that the 16:9 flag encoded on the DVD means the DVD is anamorphic.  DVD content CANNOT be encoded on disc as 16:9 native.  That's out of spec.  DVDs are standard def, 4:3 only.  All other aspect ratios are tricks (anamorphic or letterboxed).  That's one of the benefits of new HD optical media formats -- they can actually have non 4:3 native aspect ratios.  Also, ALL NTSC Standard Def video uses non-square pixel aspect ratios, not just Anamorphic video.  Most HD video now uses square pixels (Pixel Aspect Ratio of 1:1), "Standard" NTSC D1 and DV video have a Pixel Aspect Ratio of 1:0.9117, and Anamorphic NTSC D1/DV content uses a Pixel Aspect Ratio of 1:1.21557.

The DVD-Video standard specifies that the resolution on disc must be one of the following for NTSC DVDs:

    720 × 480 pixels MPEG-2 (Called full D1)
    704 × 480 pixels MPEG-2
    352 × 480 pixels MPEG-2 (Called Half-D1, same as the China Video Disc standard)
    352 × 240 pixels MPEG-2
    352 × 240 pixels MPEG-1 (Same as the VCD Standard)

16:9 content is only supported via 720x480 with an anamorphic Pixel Aspect Ratio, or via letterboxing (the cheap way).  720x480 with a standard NTSC PAR is 4:3, not 16:9.  However, all NTSC DVD video is encoded with a PAR of 1:1 (square).  That's just how it is on disc.  The DVD player reads the aspect ratio flag and then sets the PAR to either 1:0.9117 (non-square 4:3) or to 1:1.21557 (anamorphic 16:9) dynamically during playback.  It's a player feature, not a DVD-Video feature.  On disc, the pixels are square and the video is distorted no matter what.  Remember, at the time when the DVD-Video spec was developed, there was no such thing as a square pixel widescreen TV, they were all 4:3 with a PAR of 1:0.9117.  So, the developers of the spec had to figure out a way to display widescreen content in an optimal way on the 4:3 TV.  They decided to use the old Anamorphic technology (you're right, it came from the old projectors with the different lenses) but adapt it to work digitally.  The DVD player changes it's "lens" based on the the Aspect Ratio set on disc.

However, encoding to 16:9 anamorphic requires the studios to completely re-encode much of their old content.  LaserDiscs and VHS didn't support anamorphic video, so they had a large library of content already encoded digitally at a 4:3 aspect ratio with Letterboxing added to show the full frame of the video.  So, the DVD-Video spec also "includes" (means ignores really) Letterboxing.  On a Letterboxed DVD the Aspect Ratio stored on disc is 4:3.  To the player, the Letterboxed content looks no different than regular "real" 4:3 content, so the DVD player sets the PAR to 1:0.9117 (4:3).  This was not a problem until we got Widescreen TVs, because the black bars were always desired on a 4:3 format TV (it was just a choice of whether the DVD player was generating them or whether they were actually part of the video stream).  Widescreen TVs screwed this all up...

Now, two different things happen when this content is sent to a Widescreen TV.... The TV reads the incoming Pixel Aspect Ratio.  If the PAR is 1:0.9117 it centers the 4:3 image (and the black bars appear on the sides).  If the PAR is 1:1.21557 (16:9) then it fills the full screen with the content.  The problems come when you try to encode either content with a higher Display Aspect Ratio than 16:9 (such as 2.39:1 content) -- then you get black "letterboxing" bars anyway (there's no choice unless you crop off some of the image), OR when you try to display Letterboxed (4:3 with the bars built in) content on a Widescreen TV.  The TV just reads the PAR setting and centers the image with the side bars.

Maybe in the future we will have TVs that somehow scan the video content inside the frame and detect the letterboxing and then scale the content up, but we ain't there yet...

The reason those music videos (and other low-volume older content videos) are encoded so badly is that it is vastly cheaper to do it that way.  The original scans from film were done at 4:3, for VHS.  When they had to scan 16:9 content, they simply chose to letterbox it and add the actual black bars into the video scan.  Then, years later when they needed to release the same content on DVD they had three options: 1) rescan all of the 16:9 content from the original film stocks (extremely expensive and difficult -- sometimes the film stocks don't even exist anymore), 2) "digitally remaster" the content (essentially crop and upsample the 16:9 content) which is the most common choice, or 3) just dump the original 4:3 VHS scans to the DVD (which is, of course, easiest and cheapest).  They have bean counters who decide how many copies of things are going to sell, and set DVD re-release budgets based on projected sales figures.  That's why the old Queensryche video compilation you bought on DVD looks essentially the same as the VHS copy with less noise.

Oh, and about everything being okay in a HD world?  Yeah... Not so much.  The new digital cinema projectors and cameras now have their own new higher resolution (2k and 4k) and their own new aspect ratios, so it's going to be all messed up again anyhow.  They're moving slowly but surely towards a world where all major production movies are going to be shot and formatted for IMAX-style screens and resolutions, and then they'll downsample and downconvert them from there...

[jmone]

You're mostly right (and what I said was essentially the same thing but I simplified it by ignoring PAL and odd aspect ratios and whatnot). 

What...people still use NTSC...how cute!   

For those that are interested there is a good summary at http://lipas.uwasa.fi/~f76998/video/conversion/.  I especially like their section 4.9

This is really scary and nasty stuff. I thought digital video was simple! Now my head hurts!

.  & to think this is just the begining when talking video, you then have colour space, compression techniques etc etc.   

Time for a beer....head hurts again...

[glynor]

& to think this is just the begining when talking video, you then have colour space, compression techniques etc etc.   

Time for a beer....head hurts again...

No kidding.  I've been immersed in 4:2:2/4:1:1/4:2:0 color spaces, DVCPRO HD vs. XDCAM vs. HDV, tape formats vs. tapeless (flash or hard drive), etc, etc, etc ever since I got back from NAB...