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LCD delay connected to ioHD

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Carsten Orlt
LCD delay connected to ioHD
on Apr 1, 2008 at 9:54:54 pm

Just got my LCD connected to my ioHD.

Only having one I can't compare so here is my problem:

1080i25 output from the ioHD.
The LCD introduces a 1 (or 1/2) frame delay to the video compared to audio (analogue) and SD output.
My guess is that this is caused by the LCD monitor buffering both fields before displaying the progressive frame.

Can anyone confirm this as a general problem of LCD's?

If the the answer is yes how do you deal with audio sync? How to delay the audio?

Thanks!!

Carsten


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Jeremy Garchow
Re: LCD delay connected to ioHD
on Apr 1, 2008 at 10:36:42 pm

Let me get this straight.

You are sending HD material downconverted to an LCD (what kind of lcd and what connection) along with analog audio, then having the LCD reupconvert to HD and you are getting some lip slip?

Or your LCD is not matching FCP?

Jeremy




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Carsten Orlt
Re: LCD delay connected to ioHD
on Apr 1, 2008 at 10:59:12 pm

Thanks for your response Jeremy.

Sorry for not being clearer :-)

I send 1080i25 from the HDMI ioHDconnector to the LCD (using a HDMI to DVI-D adapter and connected to the DVI-D input on the monitor)

SD via RGB into my SD CRT

Audio via analogue into my mixer

Looking at the LCD HD and the SD CRT side by side the LCD has the delay.
Because the audio is in sync with the SD CRT it is not with the LCD HD.


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Jeremy Garchow
Re: LCD delay connected to ioHD
on Apr 1, 2008 at 11:43:41 pm

Got ya. Not real sure without seeing it, but your suggestions seem feasible.

What kind of LCD?


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Carsten Orlt
Re: LCD delay connected to ioHD
on Apr 1, 2008 at 11:52:20 pm

BenQ FP241W

I know I know, not the super duper thingy, but if you want to save yourself a lot of money to be able to see your HD 1080 (or whatever) at 1:1 this monitor is pretty amazing and surprisingly accurate in the colour reproduction.

After a long search and not having the money for the big guns I settled for this one.

And to be honest I'm glad I didn't spend 10x as much for the others. Grading is done in SD anyway.

But don't take my word. Always do your own testing :-)


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Jeremy Garchow
Re: LCD delay connected to ioHD
on Apr 1, 2008 at 11:57:25 pm

I understand. It's all good.

Does it have analog audio on it? Tyr sending analog audio to it straight from the ioHD and see if it's in sync then.

Jeremy




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Carsten Orlt
Re: LCD delay connected to ioHD
on Apr 2, 2008 at 12:05:30 am

Nope, no speakers on the monitor.

I have the feeling I need a audio delay processor, which I have seen for home theater setups. They have the same problem :-)

Still I can't find any reliable information that my explanation is correct?

Cheers

Carsten


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gary adcock
Re: LCD delay connected to ioHD
on Apr 2, 2008 at 12:11:30 pm

[Carsten Orlt] "Still I can't find any reliable information that my explanation is correct? "

Carsten.

You are correct, the 2 frame delay is inherent within the conversions process, it is especially evident on plasma displays. options for this issue are to try the analog video in as the HDMI process ( most likely 1.1) has to convert all signals to be progressive so the delay tends to be more apparent with P material than with Interlaced originals. (even in the 25/50i would you live in)

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




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gary adcock
Re: LCD delay connected to ioHD
on Apr 2, 2008 at 12:06:46 pm

[Jeremy Garchow] "Tyr sending analog audio to it straight from the ioHD and see if it's in sync then."

try sending analog Video TOO!!!!

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




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Carsten Orlt
Re: LCD delay connected to ioHD
on Apr 3, 2008 at 2:22:46 am

Thanks for your response Gary.

Yes maybe using analogue to the monitor would be the solution, but it would defeat the purpose of buying the monitor in the first place.
I got it so I can see the 1080i signal fully digital and 1:1 to be able to really access the sharpness and possible defects. I already noticed that just looking at the down converted SD picture doesn't give you all information and some shots looking ok in SD are not ok in HD.

Lets see what Aja might develop in the future as it happens with all LCD's be it $500 or $20,000.

Cheers


Carsten


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gary adcock
Re: LCD delay connected to ioHD
on Apr 3, 2008 at 11:02:47 am

[Carsten Orlt] "Yes maybe using analogue to the monitor would be the solution, but it would defeat the purpose of buying the monitor in the first place."

it would also solve another potential issue- most displays do not support 24/25p over HDMI since they were built with the HDMI 1.1 spec ( that means interlace only in your world- NO true P)

" I already noticed that just looking at the down converted SD picture doesn't give you all information and some shots looking ok in SD are not ok in HD.
"


I am not talking about a downconverted signal I am talking about CMPT analog HD to your display to solve the audio sync issue- and you get progressive output back.



gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




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Carsten Orlt
Re: LCD delay connected to ioHD
on Apr 3, 2008 at 10:29:44 pm

The ioHD only outputs 1080i at this stage?

Carsten


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gary adcock
Re: LCD delay connected to ioHD
on Apr 4, 2008 at 3:36:15 am

[Carsten Orlt] "The ioHD only outputs 1080i at this stage?"

not true

it is the HDMI 1.1 spec does not support 24/25 playback - it has nothing to do with the geometry - it is the same in 720p also.

The HDMI 1.1 spec did not allow for professional frame rates, since it was designed specifically for consumer use, they did not include any format that was not in the SMTPE delivery spec.

and those were only 50/60 as Interlace or Progressive depending on the frame(geometry)



gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




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Carsten Orlt
Re: LCD delay connected to ioHD
on Apr 4, 2008 at 4:14:24 am

[gary adcock] "[Carsten Orlt] "The ioHD only outputs 1080i at this stage?"

not true "


but why then can I then only select 1080i25 and not 1080p25 in either the Aja Control panel/Aja TV/FCP? and I know that 1080i25 should be actually called 1080psf25

also you confirmed in other threats that there is no 1080p television standard at this stage and all 1080 is interlaced be it 50i or 60i(59.97)

I'm totally confused now :-)

But it doesn't matter. I know that it happens (the delay) and why. and I finally can see the full 1080 signal for final judgement.

Thanks Gary!!

Carsten


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gary adcock
Re: LCD delay connected to ioHD
on Apr 4, 2008 at 12:53:52 pm

[Carsten Orlt] "but why then can I then only select 1080i25 and not 1080p25 "
you are not working in 1080p unless you recorded the content outside the camera-NO 1080 camera that I know of recording internally as true P. Unless it is recording FRAMES only.

The default format in 1080 is called PsF and is handled on playback as interlace, even though the image may have been captured as progressive. This is the same way that movies are played in the theatre with a shutter opening and closes 2x on every frame of film shown.- it smoothes the motion to the eye.

"also you confirmed in other threats that there is no 1080p television standard at this stage and all 1080 is interlaced be it 50i or 60i(59.97) "

partially correct --there is no BROADCAST standard for Satellite/ OTA transmission that is not 50i/p or 60i/p - there are deliver specs for other frame rates, just not transmission.


note that the issue with your BENq display is the HDMI connection you are using only conforms to the most primitive / basic / cheapest of the delivery standards.


gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




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Carsten Orlt
Re: LCD delay connected to ioHD
on Apr 4, 2008 at 10:57:36 pm

[gary adcock] "you are not working in 1080p unless you recorded the content outside the camera-NO 1080 camera that I know of recording internally as true P. Unless it is recording FRAMES only.
"


if nothing records in 1080p what is your point then?

sorry for being so blunt but if I work in 1080i and HDMI only supports 1080i and the ioHD only outputs 1080i using the component analogue output will not change anything??
also the delay caused by the monitor buffering the 2 fields to then display them as one will not change because I'm still working in 1080i which I can't change because I'm working with footage created by cameras and not cgi or whatever and according to your statement therefor will never be 1080p...

I just can't follow your logic?

Carsten


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gary adcock
Re: LCD delay connected to ioHD
on Apr 4, 2008 at 11:18:20 pm

[Carsten Orlt] "if I work in 1080i and HDMI only supports 1080i and the ioHD only outputs 1080i using the component analogue output will not change anything?? "

The IoHD can do more than 1080.

Your audio sync problem lies within the HDMI specs and your budget display purchase NOT the Iohd. AJA products only pass the audio thru.

However using component analog audio and video to the display will fix your SYNC issue.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




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Rob Alexander
Re: LCD delay connected to ioHD
on Apr 11, 2008 at 9:36:21 am

Carsten,

did connecting analogue component sort out the problem?



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Carsten Orlt
Re: LCD delay connected to ioHD
on Apr 12, 2008 at 12:01:30 am

I didn't try :-)
I bought the LCD so I can see a 1:1 representation of my 1080i footage. I want to do this in the best possible way meaning no signal degradation via digital-analogue conversion. I know that I can't trust the color/luminance of the LCD but that doesn't matter because I'm not using it for grading. I need to see the full HD signal on a larger screen to evaluate focus and general defects which I can't do a 100% on the SD CRT because its down-converted.
That the LCD introduces a delay because of buffering is annoying but less important to me then the cleanest signal path. I also use the DVI input on the LCD (via HDMI-DVI adapter on the ioHD HDMI output) because of the way the monitor works and allows for more picture tweaking.
Lastly Aja hinted some upcoming changes which may solve the problem.
Lets wait and see for now.




Carsten


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