No downconvert from 1080p to SD PAL

Do you have questions about Desktop Video, Converters, Routers and Monitoring?
  • Author
  • Message
Offline

Pete Berthet

  • Posts: 1
  • Joined: Sat Jun 11, 2016 2:00 am

No downconvert from 1080p to SD PAL

PostSat Jun 11, 2016 2:04 am

Hi guys,

I've got an older decklink SDI card with the latest drivers installed and im experiencing an odd problem.

If my sequence is set to 1080p in premiere I cant get any downconverted HD-> SD PAL signal to line.
However if i switch the field order to upper or lower the downconvert then works just fine.

Problem is, of course. The material I'm working with isn't interlaced so I cant quite figure out how to get around this problem.

It's particularly an issue in After Effects where it works entirely in progressive so the downconvert doesn't work at all.

Does anyone know if this is working as intended? Or have i buggered something up along the way.
Offline

Andrew Kolakowski

  • Posts: 2152
  • Joined: Tue Sep 11, 2012 10:20 am

Re: No downconvert from 1080p to SD PAL

PostMon Jun 13, 2016 6:23 pm

It doesn't work as after downscale you get 720 25p signal which is not a broadcast standard. This 720 25p signal could be send as PAL format (25p inside 50i), but it's not implemented.

When you interpret as interlaced than 1080i becomes PAL (SD 25i), so it works. The problem is that Premiere may degrade quality a lot as you "pretend" that 1080p is interlaced, so at the end you may loose half of vertical resolution (very common problem in broadcast).
Offline

Peter Cave

  • Posts: 494
  • Joined: Thu Aug 23, 2012 6:45 am

Re: No downconvert from 1080p to SD PAL

PostTue Jun 14, 2016 7:28 am

Andrew Kolakowski wrote:When you interpret as interlaced than 1080i becomes PAL (SD 25i), so it works. The problem is that Premiere may degrade quality a lot as you "pretend" that 1080p is interlaced, so at the end you may loose half of vertical resolution (very common problem in broadcast).


This is not correct. Because the original is progressive the two fields contain no motion difference and display at full resolution. Just be sure to use a progressive sequence setting for your final master output from Premiere. DV PAL & NTSC are lower field first and all other codecs upper field first.

You will only lose resolution if you throw away a field by de-interlacing. As this is only a monitoring issue, you will have no problem.
post-production starts with pre-production
Offline

Andrew Kolakowski

  • Posts: 2152
  • Joined: Tue Sep 11, 2012 10:20 am

Re: No downconvert from 1080p to SD PAL

PostTue Jun 14, 2016 9:46 am

Many software have this issue (or maybe not issue). Progressive source interpreted as interlaced case whole conversion engine goes different route (e.g. through deinterlacing step) and depending how its done it may end up badly.
Maybe Premiere is fine (specially when project is progressive), but even so this still can go suboptimal route, so before final export better to switch to progressive interpretation.

Best to test it- export 25p interpreted as 25p and 50i out of 25p project and check fine details and diagonals.
Offline

Peter Cave

  • Posts: 494
  • Joined: Thu Aug 23, 2012 6:45 am

Re: No downconvert from 1080p to SD PAL

PostTue Jun 14, 2016 11:17 am

Andrew Kolakowski wrote:Many software have this issue (or maybe not issue). Progressive source interpreted as interlaced case whole conversion engine goes different route (e.g. through deinterlacing step) and depending how its done it may end up badly.
Maybe Premiere is fine (specially when project is progressive), but even so this still can go suboptimal route, so before final export better to switch to progressive interpretation.

Best to test it- export 25p interpreted as 25p and 50i out of 25p project and check fine details and diagonals.


You are missing the point.
He is only looking for a MONITORING solution, not file output.
post-production starts with pre-production
Offline

Andrew Kolakowski

  • Posts: 2152
  • Joined: Tue Sep 11, 2012 10:20 am

Re: No downconvert from 1080p to SD PAL

PostTue Jun 14, 2016 1:04 pm

As far as I understand someone works in Premiere/AE and wants SD preview through BM card.

Preview will be fine, but this interpretation will affect whole project and processing inside Premiere or AE.
False interpretation as interlaced in AE reduces vertical resolution, so it's a bad workaround.
Offline

Peter Cave

  • Posts: 494
  • Joined: Thu Aug 23, 2012 6:45 am

Re: No downconvert from 1080p to SD PAL

PostWed Jun 15, 2016 12:04 am

Andrew Kolakowski wrote:As far as I understand someone works in Premiere/AE and wants SD preview through BM card.

Preview will be fine, but this interpretation will affect whole project and processing inside Premiere or AE.
False interpretation as interlaced in AE reduces vertical resolution, so it's a bad workaround.


Use interlaced settings for timeline while editing.
Change timeline to progressive, then render and output.
Problem gone.

It's not a theoretical solution, I do this on a regular basis for broadcast shows.
post-production starts with pre-production
Offline

Andrew Kolakowski

  • Posts: 2152
  • Joined: Tue Sep 11, 2012 10:20 am

Re: No downconvert from 1080p to SD PAL

PostWed Jun 15, 2016 9:51 am

Or simply change it on BM side, so signal is put into PAL standard, so there is no problem with preview.
Offline

Peter Cave

  • Posts: 494
  • Joined: Thu Aug 23, 2012 6:45 am

Re: No downconvert from 1080p to SD PAL

PostThu Jun 16, 2016 12:41 am

Maybe purchasing an HD monitor is the best solution. Monitoring HD timelines on SD monitors is not really a good idea.
post-production starts with pre-production
Offline

Andrew Kolakowski

  • Posts: 2152
  • Joined: Tue Sep 11, 2012 10:20 am

Re: No downconvert from 1080p to SD PAL

PostThu Jun 16, 2016 11:44 am

It's even bad idea, not just not good :)
Offline

tristansummers

  • Posts: 65
  • Joined: Tue Sep 23, 2014 2:44 pm

Re: No downconvert from 1080p to SD PAL

PostFri Jul 14, 2017 11:16 am

monitoring SD from HD timeline is fine. If you have a good monitor you have 1000 lines, so nearly 1080p in anamorphic.
I have been doing it for years. Check the pixels on HD monitor. double check the colour on the CRT.
Just monitor it interlaced. This is just like writing it psf. The progressive output is sent alternate lines. If it flickers when it is paused then it is wrong.
I used Decklink Extreme 3 and Ultrastudio 2 usung the Downconvert on SDI2

OP, the problem is your monitor can't take a progressive signal so ypu have to send it 25psf
It's a 50 Hz set so expects interlaced input
Tris
Offline
User avatar

Colin Barrett

  • Posts: 552
  • Joined: Wed Dec 05, 2012 12:23 pm
  • Location: Milton Keynes, UK

Re: No downconvert from 1080p to SD PAL

PostSat Jul 22, 2017 10:47 am

Andrew Kolakowski wrote:It's even bad idea, not just not good :)


I disagree. If one of your output options is SD then it's a very good idea to monitor in SD using a CRT Grade 2 or even Grade 1 monitor. I do this all the time for jobs where one of the outputs is SD DVD. Yes, I have public library clients who do still require SD DVD as a means of broad access to video output!
Blackmagic Teranex 2D, Ultrastudio Express, Intensity Shuttle (Thunderbolt), H.264 Pro Recorder (all Mac OSX) & lots of old VTRs used for digital archiving of legacy video formats for major libraries, broadcasters, universities and public archives.
Offline

Andrew Kolakowski

  • Posts: 2152
  • Joined: Tue Sep 11, 2012 10:20 am

Re: No downconvert from 1080p to SD PAL

PostSat Jul 22, 2017 3:36 pm

Yes, If you output also SD then it's actually very needed. As far as I understand author uses SD preview only because he has no HD setup, but he works on HD projects.
If he is working on HD masters, SD monitoring in such a case this is a compromise. You can't properly judge text overlays/credits for example. You can't see 1:1 pixels etc. There are many cases when SD preview of HD master is not optimal at all. HD monitoring is not a big investment these days- it's actually about the same as cost of SD monitoring.

Return to Post Production

Who is online

Users browsing this forum: gearbox08 and 9 guests