720 vs 704

[silikone]

Wikipedia and some sources seem to state that DVD video is 704 pixels wide, and the math behind it makes a lot of sense. However, from my experience and other sources, DVDs films take up the full 720 video width. Which one is correct?

[huhn]

both exist. this has something to do with overscan and some old zone crap combined with terrible mastering and a lot of other stuff.

so both are used.

[Sparktank]

If you make two samples (easily done in avs), one in 720 and one 704, then open them in VirtualDub,
you can change the preview aspect ratio to 40:33 pixel (DV NTSC-Wide) or 16:9 frame (Wide),
then the 704 should look the same between the two AR's when anamorphically stretched.
The 720 version will change width.

When I resize HD to SD for DVD, I always use 704.

704x480, 40:33


704x480, 16:9


720x480, 40:33


720x480, 16:9

[hello_hello]

I go by this rule of thumb.....
-All 4:3 DVDs use an ITU pixel aspect ratio, so 704x480 or 704x576 = 4:3
-Most newer 16:9 DVDs use a generic pixel aspect ratio, so 720x480 or 720x576 = 16:9
-Some older 16:9 DVDs (mainly those that have more than 8 pixels of black down each side) use an ITU pixel aspect ratio, so 704x480 or 704x576 = 16:9, but mostly they're generic.

It won't always be correct, but I'm sure it will be at least 95% of the time.

Possibly some of the reason for 16:9 DVDs being "generic" has something to do with the HDMI spec. Most HDMI players that upscale will resize to exactly 16:9 and I think if a 1080p TV is doing the upscaling, it'll generally do the same.
http://lurkertech.com/lg/video-syste...xelaspect_hdmi

This was discussed in another thread recently (at VideoHelp) and one poster said when authoring DVDs he uses a 704x480 resolution (not 720x480 with black bars). It's a legal resolution for 4:3, although there was some debate as to whether it's legal for 16:9 (I didn't think it was), but he said it solves the aspect ratio problem. It should display as exactly 16:9 now matter how the player is connected or how it's upscaled. One of the regulars tested it using his Bluray player.

Originally Posted by Sparktank

When I resize HD to SD for DVD, I always use 704.

Are you referring to a 704 resolution, or 720 with black bars? I couldn't quite work it out.

[feisty2]

713.5 x 485 = 4:3
Edit: got it wrong, should be 713.5, not 706.2

[Sparktank]

Originally Posted by hello_hello

Are you referring to a 704 resolution, or 720 with black bars? I couldn't quite work it out.

704 resolution.
spline36resize(704,480).
Fed to HCenc and then built with MuxMan.
All the 704x480 16:9 WS discs I made have turned out correctly on all devices I tried. Even an Xbox 360 at one point when I had one.

[Music Fan]

Why do you limit the resolution to 704 while you can make 720 ?
I never saw dvds encoded in 704.576, those I ripped were all in 720.576 and I always encoded in 720.576 (PAR 1,066 for 4/3 and 1,422 for 16/9).
And I had a Philips standalone dvd recorder which could encode in 720.576 and 352.576 but not in 704.576.

[TheSkiller]

Originally Posted by Music Fan

Why do you limit the resolution to 704 while you can make 720 ?

Because unlike 720 it displays the same – and correct – for every playback scenario (as we found out in this thread at Videohelp)

That includes:

• through HDMI (upscaled to HD, non-upscaled not tested)
• through analog SD connections (Composite, S-Video, Component, RGB)
• software playback on a computer


And you are never going to be able tell a difference in detail between a frame size of 704 vs. 720.

[Music Fan]

Ok, but dvd players are supposed to manage correctly 720.xxx resolutions, right ?

[TheSkiller]

Depends on what you mean by "are supposed to".

That's where the confusion starts with 720: different specs saying different things about how to handle 720.
Whereas for 704 they all concur.

If you are interested I really recommend to read the linked thread at Videohelp and others liked in that thread.

[Sparktank]

Retail DVD's and recorders will always follow standards and such. They'll probably never do 704.

At home I can do anything I want.
HCenc accepts 704x480 without issue and it's always played back in devices.
There are even settings in HCenc that allow you to create illegal MPEG2 streams (not DVD compliant).

The screenshots I took are hard to tell, but you can see for 720x480 in 40:33, it's wider than it should be.
704x480 is the same no matter what when anamorphically stretched.

There's a lot of old posts in the forum talking about 704 and 720.
I spent a couple days going through a lot of them before settling on 704 (and then forgetting most of the details why):

Originally Posted by TheSkiller

The width for a standards-compliant DVD does not have to be 720 (for both NTSC and PAL), it can be also 704 and I would recommend to use 704 to avoid the dreaded ITU vs non-ITU issue.

[Sparktank]

And the time it took dig up old posts, TheSkiller chimes in.

[Sharc]

Originally Posted by Music Fan

....I never saw dvds encoded in 704.576, those I ripped were all in 720.576 and I always encoded in 720.576 (PAR 1,066 for 4/3 and 1,422 for 16/9).
And I had a Philips standalone dvd recorder which could encode in 720.576 and 352.576 but not in 704.576.

But there are a lot of (older) ITU-conformant and correctly authored DVDs with active picture width of 704 plus black borders (pillows) padding to 720. Unfortunately most (if not all) digital HW gear (HDMI) play these DVDs slighly horizontally distorted at 4:3 or 16:9 including the left+right borders, but who cares .....

[silikone]

I took a look at the Big Buck Bunny DVD master, and even that seems to be encoded at borderless 720x480, so the NTSC wide pixel aspect ratio would stretch it too much. Disappointing considering it's a film often used as a showcase of all the newest video technologies.
Do most pre-HDMI DVD players crop out the 16 rows?

[Sharc]

From my experience:
- Legacy analog DVD players connecting via SCART to the TV will stretch the picture according to the ITU Pixel Asect Ratio. Means that a 704 wide active picture (8+704+8) will be displayed at its correct width. The 2*8 black borders are actually not cropped but will normally just fall outside the visible area of the TV screen. When you play the same (8+704+8) DVD via HDMI you will normally see the black borders, and the active picture is slightly (about 2%) too narrow.
- DVDs which are using the full 720 width for the active picture are (normally) using the "generic" pixel aspect ratio. They will playback undistorted (i.e. at correct width) via HDMI. However, when you play the same DVD on an legacy analog player (via SCART) the picture is horizontally stretched slightly too much (about 2%) and some (2x8 pixels) may drop outside the visible TV screen area.

In any case the errors are small.

[Music Fan]

If I understand correctly, encodings in 720.xxx would never be a problem if the appropriate PAR was used ; videos in 704.xxx with black borders to make 720.xxx should use the same PAR than 704.xxx videos (without black borders).
The question is : why do some encoders (I mean people making encodings) add black borders on 704.xxx videos to make 720.xxx instead of leaving it in 704.xxx (or why don't they crop these black borders if the original video already contains black borders), which creates confusion ?
Thus the problem is not the resolution but the PAR, unless some PAR are not handled by some players or TVs.

[Sharc]

Originally Posted by Music Fan

If I understand correctly, encodings in 720.xxx would never be a problem if the appropriate PAR was used ; videos in 704.xxx with black borders to make 720.xxx should use the same PAR than 704.xxx videos (without black borders).

Yes. But unfortunately you won't find the PAR in the DVD video streams or .vob containers. Only the studio knows which PAR they have actually been using.

The question is : why do some encoders (I mean people making encodings) add black borders on 704.xxx videos to make 720.xxx instead of leaving it in 704.xxx (or why don't they crop these black borders if the original video already contains black borders), which creates confusion ?
Thus the problem is not the resolution but the PAR, unless some PAR are not handled by some players or TVs.

Well yes, but the PAR is actually not the problem but - if handled correctly - it would be the solution.
Most (all?) Digital (HDMI) HW players and TV's unfortunately ignore the PAR - even when it is signaled in the stream or container. They simply follow 4:3 or 16:9 display aspect ratio (DAR) instruction, nothing else.
SW players like MPC-HC can read the PAR (or --sar of an h.264 stream for example) and stretch the picture accordingly, rather than just mapping it to either 4:3 or 16:9.

Added:
More about standardized PAR see here:
http://forum.doom9.org/showpost.php?...7&postcount=11