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HD material transcode to SD - quality lost

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HD material transcode to SD - quality lost
by Robert Kreuz on Apr 24, 2009 at 9:57:37 am

Hi Folks,

searching for a good way to transcode HD material to SD without losing the highlights and sharpness of the HD original.

My current working process in Avid is following:

Make my cut complete in HD, for effects, renderings, etc. I use DNHD 185x Codec. All looks fine. Well, if I want now a SD playout from my timeline, first step I change the projectformat to PAL. Only this step brings a very high grad of qualitylost. Yes, the qualitybotton is switched to green. But the image looks very blurrish. Second step, in this PALswitched project I make an 1:1 videotranscode of the timeline, it brings me the HD footage to PAL. The result is a little better than without doing a transcode, but the image is not so brilliant like the original HD one. I lost some details in the highlights and an amount of sharpness.
I tried also this way. Export a HD Quicktime and imported into a PAL project. Result is also poor.
Is where a correct way to do convert HD to SD only in Avid. Don`t want to use third party software. I think, also in SD you must have the possibility to keep the brilliance of the original HD footage.

Whats your resolution ?

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Re: HD material transcode to SD - quality lost
by Shane Ross on Apr 24, 2009 at 11:02:55 pm

[Robert Kreuz] "searching for a good way to transcode HD material to SD without losing the highlights and sharpness of the HD original."

The whole reason the world loves HD is because it is sharp and has great highlights. Much more than SD. This is called RESOLUTION...HD has more resolution than SD. More scanlines...a LOT more. SO it looks tons better. Take many of those scanlines away and it won't look that good. So I think your expectations on how good it SHOULD look are a tad high.

[Robert Kreuz] "I think, also in SD you must have the possibility to keep the brilliance of the original HD footage."

No...there isn't. That is why the world is shifting to broadcasting and delivering HD over SD. it looks better.

With Avid the best you can do without Avid hardware is Transcode...but that transcode is pretty good. If you had the hardware, like Nitris or Mojo or Adrenaline, then you can downconvert when you output to tape.

Shane

GETTING ORGANIZED WITH FINAL CUT PRO DVD...don't miss it.
Read my blog, Little Frog in High Def

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Re: Resolution
by Robert Kreuz on Apr 24, 2009 at 11:39:26 pm

@Shane,

understanding your point, theoretical this is a possible solution. But practical think about this:

1. Take a hardware based downsizing via HDcam deck or blackmagic cards
you get a SD result looking like the HD footage.

2. Take an ordinary photography size it down via photoshop or something like, you will not lose any detail.

HD has 1920 x 1080 pixel at 72dpi SD 720 x 576 at 72 dpi. The Resolution is the same only the "face" is bigger.

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Re: Resolution
by Shane Ross on Apr 24, 2009 at 11:49:21 pm

[Robert Kreuz] "1. Take a hardware based downsizing via HDcam deck or blackmagic cards
you get a SD result looking like the HD footage."

CLOSE...but yeah, it looks phenominal. WHY? Because the Terranex does a freaking phenominal job of doing this. If you could get the same results via transcoding, the Terranex wouldn't be able to make a living. Software solutions never look as good as hardware...they can't. I don't know all the technical reasons, but there are a lot of them.

[Robert Kreuz] "2. Take an ordinary photography size it down via photoshop or something like, you will not lose any detail. HD has 1920 x 1080 pixel at 72dpi SD 720 x 576 at 72 dpi. The Resolution is the same only the "face" is bigger."

DPI is meaningless in video. Video has no DPI...no DOTS PER INCH. DPI is for print work and photography...zero place in video. Video is reosolution dependant...1920x1080...pixels. 720x486...pixels. Less pixels will be less resolution.

But yes, the Terranex rocks...and you will not get near the same results with software downconverts. The Avid hardware does a decent job...better than software, but not as good as a Terranex.

Shane

GETTING ORGANIZED WITH FINAL CUT PRO DVD...don't miss it.
Read my blog, Little Frog in High Def

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Re: DPI meaningless
by Robert Kreuz on Apr 25, 2009 at 6:01:20 am

Seems I must find a workaround with my Blackmagic Card.

DPI is meaningless in video. No time to discuss fully this. It`s another chapter and belongs not to the thread.

Thanks for sharing experience.

Robert Kreuz
http://www.feuerundauge.com

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Re: HD material transcode to SD - quality lost
by Dino Sanacory on Apr 26, 2009 at 4:54:54 pm

How are you monitoring HD versus monitoring SD?

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Re: HD material transcode to SD - quality lost
by Robert Kreuz on Apr 26, 2009 at 5:03:08 pm

Monitor via LCD Display (Full HD) HDMi connected and Class 1 CRT

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Re: HD material transcode to SD - quality lost
by herbid mulyo on Apr 27, 2009 at 1:50:47 pm

Try this.

From HD Project, Export as Quick Time MOvie. Setting Same As Source, 610/709 and Native Dimension of Aspect Ratio.

And then you make new Project of 25i PAL.

Import your Quick Time HD in Video Resolution of 1:1 MXF, 610/709 Non Square.

Maybe it helps. Like to hear the result.

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Re: HD to SD - solution found
by Robert Kreuz on Apr 29, 2009 at 8:56:01 am

1. Export "Same as Source" don`t work with XDcam EX footage.

2. Tried to export my HD timeline as Qt with DNxHD185x codec. Than I imported that into an ordinary PAL project. The result was the same like doing a transcode or videomixdown to SD resolution. The hole sharpness fly away.

3. Tried an export from my HD Timeline (projectformat was 1920x1080) to an uncompressed QT with a SD resolution (720x576). Result = perfect. Sharpness, highlights and brilliance like the HD footage only smaller.

Hope somebody can help my experience.

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