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Kona to Kona Downconvert

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Paul Nelson
Kona to Kona Downconvert
on Dec 21, 2011 at 6:50:13 am

Hey there FCP/Kona Jedis.

I come from an Avid background, but am in a position where I have to support some FCP 7 edit suites. So please bear with my ignorance in this regard.

I'm trying to do a Kona to Kona downconvert of 720p 25fps to 625i (I'm in PAL land).

In theory it sounds like a piece of cake. Playout my HD timeline and capture into the other suite.

Playout system is a Kona LHe, capture system is a brand spanking new 8core running Lion and a Kona LHi. Capture system FCP setup with easy setup 625i ProRes 422.

Everything is over SDI.

Ok, firstly. Does it matter which card is doing the downconvert? Should it happen on output or input or doesn't matter? I've chosen on input, as it's the newer machine and newer hardware, higher spec etc etc.

Secondly... So I've now got my footage captured in, but I'm a bit perplexed as to what I'm seeing. I assume that when I do a downconvert to an SD interlaced format that I should actually see the interlacing? It all looks progressive to me both in FCP and in Quicktime. Except one clip, which is really throwing me, as it came from the same HD timeline (I stopped and started to make some separate clips).

So to summarize. Output 720p 25fps in a ProRes 422 sequence out of Kona Lhe into 625i easy setup Kona Lhi.... what am I doing wrong? Shouldn't it be interlaced on input? Why is only one clip showing the interlacing.

Very perplexed.

Thanks for the help.

Cheers,
Paul


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walter biscardi
Re: Kona to Kona Downconvert
on Dec 21, 2011 at 1:53:47 pm

[Paul Nelson] "Ok, firstly. Does it matter which card is doing the downconvert? Should it happen on output or input or doesn't matter? I've chosen on input, as it's the newer machine and newer hardware, higher spec etc etc."

Nope, not really, though we generally do the same thing you're doing. Machine 1 plays out natively, Machine 2 makes the conversion and records.


[Paul Nelson] "Secondly... So I've now got my footage captured in, but I'm a bit perplexed as to what I'm seeing. I assume that when I do a downconvert to an SD interlaced format that I should actually see the interlacing? It all looks progressive to me both in FCP and in Quicktime. Except one clip, which is really throwing me, as it came from the same HD timeline (I stopped and started to make some separate clips). "

Ok, on Machine 2, the record machine, have you set that up to properly do the conversion? You set up the conversion via the AJA Control Panel, not through FCP. So when you look at the AJA Control Panel you should see the 720p / 25 signal coming in and then being converted to the 625i signal. This all happens BEFORE the signal gets to FCP.

So under Format in the AJA Control Panel, the Primary should be 625i and the Secondary should be 720p / 25.

You have Machine 2 set up correctly with FCP in the 625i Easy Setup. Now just make sure you have the conversion set up correctly in the AJA Control Panel.

Walter Biscardi, Jr.
Editor, Colorist, Director, Writer, Consultant, Author, Chef.
HD Post and Production
Biscardi Creative Media

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AJA Sales Department
Re: Kona to Kona Downconvert
on Dec 21, 2011 at 5:56:56 pm

If you need assistance with configuring conversions, please feel free to contact AJA Technical Support via phone or email between 9am and 5pm PST.

In brief, a 720p 25fps timeline is output over baseband video as 720p 50 (720p 25 is not an "over the wire" format). So there are two choices since you own two AJA products, both of which are capable of hardware based downconversion.

The simplest path would be to set your output AJA product to downconvert 720p 50 to 625i 25; you accomplish this in the Format tab by setting the Primary Format as 720p 50 and the Secondary Format to 625i 25. Then for the SDI output, select the Secondary Format. You will see the downconversion icon in the AJA Control Panel signal diagram. On the input AJA product, simply set it to capture 625i 25.

Alternatively, if you wanted, you could elect to simply send 720p 50 out of the output AJA product - without any conversions - and set up an incoming conversion on the input product. On the input product, you achieve this by setting the Primary Format to 625i 25 and the Secondary Format to 720p 50; if you do this, you will notice that the downconversion icon will appear on the incoming video signal when you look at the icon in the AJA Control Panel.

Again, if you have an issue configuring this, please feel free to contact AJA Technical Support.

--
AJA Video Systems
+1 (530) 274-2048 Intl.
(800) 251-4224 US
sales@aja.com


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Paul Nelson
Re: Kona to Kona Downconvert
on Dec 21, 2011 at 8:54:22 pm

Thanks for the help guys.

Upon further investigation I think I may have discovered a bug, or perhaps it's a Lion/FCP/Kona combination thing. I'm running the latest Lion updates and the 10.0.1 Kona driver.

I did the following tests:

On capture machine chose easy setup for Pal 625i Pro Res 422. Opened AJA control panel to choose secondary format 720p. Played out 720p from playback machine via SDI.

I noticed the following:
While in the capture tool you can visibly see the interlacing, or in my case, sometimes not. When reviewing captured footage I've verified that indeed sometimes the captured footage is coming in progressively, sometimes interlaced (as I want). By stopping/starting playback on the playout 720p machine, the capture machine seems to 'wake-up' and digitize interlaced (or sometimes not..grrr). There seems to be no rhyme nor reason for this, as it also could continue to capture progressively. Reviewed footage shows the same. I could see within the same captured clip some parts progressive and some interlaced simply by stopping and starting playback on the 720p timeline.

I've also tried the other way round.

Did the downconvert on the the playout machine so that it was sending a 625i signal straight to the capture machine. I noticed the same results as above. By stopping starting the playout, the capture seems to 'wake up' and do interlacing.

Any further suggestions/settings/etc I should look at? Does FCP have some built in de-interlacing I'm not aware of that I need to control somehow?

I know my setup isn't ideal as I'm running Lion and unsupported FCP and etc. But that's how the machine came to me. I just wanted to make sure I wasn't doing anything obviously wrong.

Cheers,

Paul


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AJA Sales Department
Re: Kona to Kona Downconvert
on Dec 22, 2011 at 1:55:11 am

It sounds like you are evaluating interlacing using the FCP desktop display; this draws a field, not a whole frame and would explain why you sometimes perceive the footage captured as interlaced and sometimes not. A better method of evaluating interlaced material would be a CRT.

Again, please feel free to contact AJA Technical Support if you have questions about conversions; they will be happy to assist you.

--
AJA Video Systems
+1 (530) 274-2048 Intl.
(800) 251-4224 US
sales@aja.com


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Paul Nelson
Re: Kona to Kona Downconvert
on Dec 22, 2011 at 7:39:02 pm

Thanks. I've sent a request into tech support.

This won't be a frequent part of my workflow, so it isn't crucial.

But on inspecting the footage both at 100% in FCP and in external software, quicktime/vlc/etc... it is indeed either progressive or interlaced on the same clips and same capture instead of being interlaced the entire time.

Thanks for the help guys. At least it sounds like my methods are correct.

Cheers,
Paul


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AJA Sales Department
Re: Kona to Kona Downconvert
on Dec 22, 2011 at 11:13:55 pm

You are using software tools/desktop applications to evaluate interlacing (these do not tend to support frame analysis of interlace as computer displays are progressive). The suggestion for using a CRT was the external video output of the KONA to a broadcast quality SD monitor. Note that non-CRT based viewing devices, like LCDs, are not great for evaluating interlaced material as they typically have de-interlacers built into their design.

--
AJA Video Systems
+1 (530) 274-2048 Intl.
(800) 251-4224 US
sales@aja.com


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Paul Nelson
Re: Kona to Kona Downconvert
on Dec 22, 2011 at 11:39:00 pm

Thanks for the information.

However, I'm not evaluating the quality of the capture. I'm simply determining if the captured footage is interlaced or not, which is quite easy to do with software tools. Either the footage exhibits the combing artifacts or it doesn't. And when I can see the exact same clip captured with the exact same settings/method as being interlaced or progressive then there is inconsistency in the capture/downconvert.

Even during capture I can see visually whether it is coming in interlaced or not, and it randomly changes during capture when I stop/start the playback machine all within the same clip. So the same clip is containing both progressive and interlaced frames. To me, the SD downconvert to 625i should be coming in interlaced 100% of the time.

I was just trying to determine whether it was the card/driver as it's a new purchase, or the capture tool of FCP that was altering what is captured. It appears to me it is the capturing machine, as when I performed the downconvert on playback out of the other kona as described, it still exhibited the same behavior.

Eventually I will try capturing through a different program (Avid) and see if there are any issues on a downconverted capture. But for now I just don't have the time.

Cheers,
Paul


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Jeremy Garchow
Re: Kona to Kona Downconvert
on Dec 23, 2011 at 12:42:50 am

Actually, if converting 720p25 over 50, you should get 25 psf on the other end (25p wrapped in 50i SD). In the capture machine control panel, what is the listed incoming format next to the SDI in?

You have 720p25 VFR selected in the playback machine?


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Paul Nelson
Re: Kona to Kona Downconvert
on Dec 23, 2011 at 4:56:13 am

It's full frame rate 720p out of the playback machine. Wouldn't know where to check for VFR. Everything is set to 'high' or 'full'.

Control panel is showing indeed 720p SDI in, and showing the downconvert icon to the 625i primary format. It all looks correct.

I can fire up the capture and view the process. And by watching the capture window I can either see the interlacing happening or not. If it looks progressive to me I stop/restart playback on the playout machine until I see interlacing, and then let the capture continue. This seems to work.

I have test clips that indeed show this happening... You can see the smooth progressive footage, I stop/restart the playout machine until the interlacing 'wakes up' and then let it rip.

It's all a bit odd, and done my head in a bit.

Even when I send a 625i downconvert from the playback machine I've noticed the same phenomenon, so it seems to point to my new setup.

New Mac Pro, new kona, new OS. Who knows. Was hoping someone else may have seen the same.

Cheers for all the input.


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Matthew Causon
Re: Kona to Kona Downconvert
on Dec 23, 2011 at 10:48:45 am

Hello Paul

Did you receive a response form AJA Tech support? (I think you had mentioned you had sent in a request?)

If not please feel free drop me you email address and I will have someone contact you.

PS Are you UK based?


Best regards

Matty Causon Phosphor
EMEA Representation for AJA Video Systems Inc.
matty@phosphor.pro
http://www.phosphor.pro


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Jeremy Garchow
Re: Kona to Kona Downconvert
on Dec 24, 2011 at 4:06:09 am

[Paul Nelson] "Control panel is showing indeed 720p SDI in, and showing the downconvert icon to the 625i primary format. It all looks correct. "

Good deal.

[Paul Nelson] "I can fire up the capture and view the process. And by watching the capture window I can either see the interlacing happening or not. If it looks progressive to me I stop/restart playback on the playout machine until I see interlacing, and then let the capture continue. This seems to work."

But as has been mention, Paul, what you are seeing is not what what your final image might represent. As was mentioned. 720p25 will become 625 psf. This means your progressive images are stored and sent in an interlaced stream (every frame, of which the 720p25 stream becomes 720p50 (2:2 pulldown) becomes a field. Since each frame is doubled, those double frame will become a field, which means you will ahev two fields that are the same, then two fields that are the same which makes psf. Since the FCP capture window you are watching is not setup to display proper interlacing, what you are seeing does not represent the final image. A CRT or broadcast capable flat panel monitor would be the only true way to view your images as intended. Stopping and starting the capture is not going to change the playback and should not be used in confidence.

Maybe you might have a monitor that you can hook up to the record system Kona outputs?

Jeremy


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