Quantcast 720x576 vs 702x576, PAR confusion? - digitalFAQ Forum
  #1  
10-26-2019, 09:08 AM
SFtheGreat SFtheGreat is offline
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I need to settle this once and for all.

The proper PAR and SAR for PAL SD material.

The 720x576 SAR is the standard for both 16:9 and 4:3 material.

But the problem starts when PAR and nominal analogue blanking come into place.

VLC displays content in 1,067 PAR, which is correct for 720x576 DV video (720*1,067=768), however VEGAS uses 1,094 PAR, that is correct for 702x576 which is the ITU standard (702*1,094=768) and when 702 active pixels are inside 720x576 raster with 18 pixels of nominal analogue blanking on both sides, however then it looks like this 720*1,094=788 with proper 702->768 inside with blanking on both sides.

When transfering VHS tape into DV codec the resulting 720x576 has blanking on sides and the active video is 702x576 that should use 1,094 PAR, however VLC will play it with 1,067 wrong PAR (custom aspect ratio does not fix the screenshot however), Vegas will use correct 1,094 PAR.

Now the opposite situation happens with DV 720x576, VLC plays it correctly at 1,067 PAR, but Vegas will stretch it with 1,094 PAR.

The problem I have, is that I have no idea which PAR to use to master an SD project for VHS transfer, should I use full 720x576 resolution with 1,067 PAR, or should I use ITU resolution of 702x576 active image inside 720x576 container with blanking 18 pixels and PAR of 1,094.

It would be very helpful, if wikipedia articles about D1 and D2 tapes would specify which PAR they used, as they were primary masters for VHS tapes back in the day.

Not to mention that some sources say PAL was 704x576 with totally different PAR, (https://en.wikipedia.org/wiki/Standa...ion_television)...

Or is DV 720x576 in 1,094 PAR and the additional 18 pixels are simply the overscan, that should not be visible on TV, but is visible on PC and should be exported as 788x576 square pixels?

PAL user, unless otherwise specified I talk about PAL equipment.
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  #2  
10-26-2019, 09:19 AM
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lordsmurf lordsmurf is offline
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702x is not compliant to anything.

Remember that any low-knowledge keyboard warrior can add/edit to Wikipedia, and many do. It's not an authoritative source. In fact, you often have no idea who the random source is. Wikipedia has a real problem with parroting myths at times, referring to equally false "sources". Wikipedia is good for leads to actual sources, but you must be careful. This is general advice, not referring to any specific entry.

Software is often wrong, as programmers are rarely video folks. If you think a program is doing something dumb, odds are it is. For example, since it's inception, Adobe Encore was a POS, and I often mentioned it. It's about as professional as AIO freeware. It's both obtuse and has ridiculous limitations that don't exist in the authoring specs. It's dumb software that was eventually abandoned by Adobe, and nobody misses it.

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  #3  
10-26-2019, 09:39 AM
SFtheGreat SFtheGreat is offline
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Quote:
Originally Posted by lordsmurf View Post
702x is not compliant to anything.
Well, it is to ITU-R and therefore REC.601. The active image in ITU 720x576 is 702x576, the side lines are blanking and the PAR for this is 1,094 so that the 702 is stretched to 768 square pixels for 4:3 DAR.

Wikipedia lies, everybody knows that.

The bottom line is, should 720x576 DV be displayed at 1,067 or 1,094, and therefore should I master to 720 with 1,067, or 1,094 with blanking bars at sides?

And apparently the whole 704 in PAL comes from MPEG limitation:
https://www.linuxtv.org/mailinglists.../msg00152.html
While 704 is correct in NTSC.

Last edited by SFtheGreat; 10-26-2019 at 09:57 AM.
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  #4  
10-27-2019, 07:15 PM
msgohan msgohan is offline
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There have been gigantic threads on the Doom9 forum over the years about the differences, the degree to which they matter, and the degree to which people producing content in the first place actually bothered to follow the standards.

Here is another page you can read: https://web.archive.org/web/20120313...eo/conversion/

I think Charles Poynton's book mentions some details but not all of the "controversies".
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  #5  
10-28-2019, 12:58 AM
SFtheGreat SFtheGreat is offline
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That has many details I'll look over.
However those are good links as well:
https://web.archive.org/web/20050211...turesize.shtml
https://www.mikeafford.com/blog/pal-...5e9Gmd2UcVvoBk

All the above mean, that DV video from camcorder has unnessesary pixels at sides that won't be visible on TV instead of using them as blanking.

To conclude the 1,094 PAR is the proper one for PAL and VLC is not displaying PAL image properly, but the video itself is carrying 4:3 flag, which is correct for active image, but not taking blanking/overscan into account.

PAL user, unless otherwise specified I talk about PAL equipment.
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