DVI>HDMI Poor picture quality, grainy / combing

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Level 1

5 points

DVI>HDMI Poor picture quality, grainy / combing

Hi Guys,

Have just purchased a 26" Samsung LCD and have it connected to my G5 via a DVI-HDMI cable. However, full-screen playback on the monitor from FCP looks really poor- very grainy, with lots of combing (Note: the LCD autodetected a 50hz/1920x1080 interlace setting).

I know FCP has this setup as a CINEMA DISPLAY PREVIEW so its not really full-quality, but even still- it looks worse than when i was using a tv attached via S-Video!

Would anyone be kind enough to share what i might try to address the problem? i have already tried the obvious altering resolutions etc- but to no avail...it has me confused!

Many thanks,

Adam

Dual Processor G5 (2Ghz), Mac OS X (10.5.6), KRK Rokit 8 Monitors, 2.5 GB RAM, 1TB Lacie FW Drive, 250GB HDD internal, PS3 for Blu-Ray! :)

Posted on Jan 6, 2009 6:42 PM

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Answer 1

Shane Ross

Level 8

43,110 points

Jan 6, 2009 6:57 PM in response to Chocboy

I know FCP has this setup as a CINEMA DISPLAY PREVIEW so its not really full-quality

Yup...that's it. It isn't full quality, it is a lower resolution to ensure that no skipping of footage occurs (dropped frames).

even still- it looks worse than when i was using a tv attached via S-Video!

That was via firewire to a DV device, correct? Because that IS a proper FULL RES signal, so yes, it will look better. DVI out means that it is sending a COMPUTER signal, not a VIDEO signal...so the quality is worse.

Would anyone be kind enough to share what i might try to address the problem?

Yup...get a capture card. With a G5 your options are limited. NO Decklink Intensity with HDMI out...no Matrox MXO with HDMI out. The MXO will do DVI to a computer monitor and clean up the signal, but you can't convert that DVI to HDMI I don't think...messes up the signal. BUT, you could use the MXO and go COMPONENT to that monitor. That would be a good signal. Otherwise you are looking at Decklink HD cards or Kona LH...the Decklink might be comparable in price to the MXO.

Shane

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Answer 2

Chocboy Author

Level 1

5 points

Jan 7, 2009 3:09 AM in response to Shane Ross

Shane,

Thanks for getting back to me so quickly 🙂 Actually not on this occasion - it was just straight to a TV (really rough and ready preview as it were) - had the apple dvi/s-video adapter on my graphics card.

As a temporary solution though, would perhaps a DVI-DVI connection be at least somewhat better? or perhaps even reverting to the s-video as before? (though i know it won't send High def signal... reduced data rate)...

Many thanks,

Adam

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Answer 3

Jan 7, 2009 9:30 AM in response to Chocboy

The reason it looks rubbish is because the TV is incapable of displaying a 1:1 representation of a Mac desktop at either 1080 or 720 irrespective of whether its 50 or 60Hz.

The panel most likely has a naitive res of 13XX x 768 and is therefore incapable of showing a true 1:1 HD image.

The closest you will get is setting the monitor to exactly match the source material under monitor settings.

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Answer 4

Chocboy Author

Level 1

5 points

Jan 9, 2009 5:54 PM in response to Steve Mizen

Steve, i apologise for my delayed response....

I understand your point, however i don't see how differing resolutions could cause combing- with my previous setup (as above) i had my G5 connected to a silly little CRT tv for a quick fix and didn't have this problem at all - it had no combing or graininess...

As I mentioned before, would changing to DVI > DVI or another cabling method resolve/improve the issue?

Many thanks,

Adam

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Answer 5

Jan 10, 2009 2:45 AM in response to Chocboy

Hi,

Ok, what I was trying to establish is that the setting the monitor auto selected matches the settings you are working to ie you are working in PAL and the monitor has selected the frame size and sync rate correctly.

If I connect a MacBook to a TV here using a DVI to HDMI lead I can set the monitor to 1080 60Hz and still play back 1080 50Hz on it however the signal will be ghosted.

When I set the monitor to 1080 50Hz and playback 1080 50Hz its fine.

If your settings are correct I would suspect that the HDMI lead is not very well shielded and is picking up interference from a nearby mains source or that the TV and computer are on different mains supplies and are out of sync.

Ideally under the monitor control panel you should be able to select the monitors native resolution of 13XX x 768 for optimum display results at your native sync rate.

So there are a few things you might try

HTH's

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Answer 6

Chocboy Author

Level 1

5 points

Jan 11, 2009 9:24 AM in response to Steve Mizen

Steve,

I have tested the TV at the monitors 13XX x 768 resolution (as well as others) - though if i choose anything other than the auto-detected resolution (as mentioned above) then Final Cut simply displays a White screen for preview....

I am doing something silly still i am sure - but could you explain why this is happening now?
Many thanks,

Adam

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Answer 7

Jan 11, 2009 10:46 AM in response to Chocboy

You may have to reassign the monitor as the output device in FCP's video preview settings.

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