PAL 704 x 576?

Tim Stannard wrote on 9/16/2007, 4:06 AM

Just installed 4.5 and in resetting up all my defaults I was reminded of something I'd noticed before but not got around to querying and promptly forgotten about.

In DVDA the Vedio format can be 704 x 576 (PAL) OR 720 x 576 (PAL) NTSC has similar horizontal pixel options.

These options do not exist in Vegas - it's always 720.

So, my question is basically why the two choices and when would one use 704 rather than 720?

Comments

Kennymusicman wrote on 9/16/2007, 5:03 AM

Don't quote me on this - but a quick google of "704 576" yielded
http://forum.videohelp.com/topic94382.html

(snippet taken for you)
The official (legal) resolutions for optical media are:

720 X 576 (480 NTSC). Used by most DVD.
704 X 576 (480 NTSC). Used by some DVD
480 X 576 (480 NTSC). Used by SVCD
352 X 576 (480 NTSC). Used by DVD and China Video Disc (CVD). It is also the "official" SVHS resolution, determined by the creator of HS, JVC.
352 X 288 (240 NTSC). Used by VCD and DVD. It is also the "official" VHS resolution, determined by the creator of VHS, JVC.

The official names for those resolutions, come from the US. Those names are:

720 X 576 (480 NTSC): Full CCIR-601 , or CCIR-601 D1. It is the Full PAL/NTSC Studio resolution. Most of the time, people call it simply CCIR-601
704 X 576 (480 NTSC): CCIR-601 1/1 D1 or cropped CCIR-601 D1. Most of the time, people call it 1/1 D1. Very rare, you can see this resolution as 702 X 576/480. It is the TV Broadcast resolution
528 X 576 (480 NTSC) is defined as 3/4 D1. It is supposed to be the Laser Disc resolution, but ain't. I'll explain later
480 X 576 (480 NTSC) is defined as 2/3 D1. It is the SVCD resolution.
352 X 576 (480 NTSC) is defined as 1/2 D1. Used by DVD and CVD
The VCD resolution is 352 X 288 (240 NTSC) and it is called CIF- 601.

In some parts of Europe and especially Far East Asia, people tend to use other names to describe the legal DVD - Video resolutions. So, very often you see or read the terms D1, D2, D4 and D3 . Those names stands for:
D1 (or D-1) for 704 X 576
D2 (or D-2) for 352 X 576
D4 (or D-4) for 352 X 288
D3 (or D-3) stands for the 704 X 288 framesize. This resolution is very interesting, because is totally useless but fully supported by DVD - Video!
Those names are basically used a lot for -X- formats PAL based. Most known are the D4 DVD (a DVD with VCD resolution and VCD bitrates mostly VBR) and D2 DVD, which is a DVD-R with 1/2 D1 resolution mpeg 2 files. Many also call as "D4 SVCD", the xSVCD with a VCD resolution/bitrate. Those names are unofficial, so better use the US name system

Tim Stannard wrote on 9/16/2007, 1:19 PM

Thanks for posting the link, Kenny.

quick google of "704 576" yielded

Slap on wrist taken. Having done a search on this forum and come up with nothing I figured tryinging a similar search on Google would return so much unrelated stuff as to be worthless. Obviously I was wrong.

Anyway the thread was mildly interesting and answered my supplementary question (why use it):

So I guess I don't need to worry about that too much.

Kennymusicman wrote on 9/16/2007, 1:50 PM

Glad you got the answer then.

With the plethora of standards around, sometimes we all wonder what some of them are for. Afterall, 720x576 and 720x576 widescreen have the same damn resolution... teehee

Ken

MPM wrote on 9/16/2007, 9:05 PM

Tim, very oversimplified, on a PC video has different pixel aspect ratios possible. 720 width is actually somewhat comparable to the old 640 width -- the difference is the pixel aspect that accounts for them not looking the same. A DVD player or most hardware for sending video to a std TV will automatically scale the picture so 720 looks correct, and most don't know quite how to handle 640 any longer.

Why go thru all that? Well, I said *Somewhat comparable*. The conversion between D1 spec 720 width video and square pixel 640 width video actually involves cropping the frame slightly. Once you crop the frame, you can't quite go back -- 704 is the best you can manage. So 704 video is what you get when you take 640 video and convert it so that a DVD player will scale it correctly on your TV. If you have any DivX video for example that you downloaded, and it is square pixel, playing without distortion on your PC, it should be sized to 704 before you put it on DVD.

Still pictures get sized to 655 width, precisely because they still have the extra 15 pixels or so to make it all the way to 720. And yes, those are NTSC specs but PAL works the same way -- just different conversion math.

Edit: almost forgot...
Overscan is the areas which typically contain the extra data for the std TV. When you crop off the extra pixels to get from 720 to 640, you might or might not cut off any useful picture data, depending on what the source of the video was. Typically the only place you'll see overscan is with a broadcast signal, and typically the only place you'll see black bands on either side of your video is from some capture hardware.

Does 704 save bandwidth? Well yeah, but the folks that want to save bandwidth (like cable and sat companies) usually take it a lot further than that. After all, halve your 720 width and it'll still fill a TV screen. I'm not saying that a cable company will go that far, but they generally don't stop at 704.