-
When is Digital not Digital? Firewire or SDI?
-
[walter biscardi] “If you capture DV25 via Firewire and DV25 via SDI, they are one and the same quality. If you capture DV25 to Uncompressed SD 8bit, they are one and the same quality.
It is only after you apply any type of filtering or graphics that the advantages of an uncompressed timeline will be evident.”
Again, respectfully, this is simply not the case. Have you ever actually done the test? Consider this – when you put a DV25 tape in a deck that has an SDI output, is the deck not doing a hardware conversion from the DV codec to an uncompressed SDI stream? It IS. Therefore, it cannot be an identical copy to what comes in via firewire which is supposedly native DV – having undergone no conversion until it is decoded (via software) in the mac. Now I know theoretically the act of modifying those ones and zeros in any way is normally considered bad, but the effect of converting the DV25 footage to an uncompressed SDI stream via hardware in my deck has a visable and pleasing effect. It does look better than DV25 captured via firewire. Do the comparison, blow up both captures in AE to %400 and look at something red. You’ll see a difference. Sometimes reality, no matter how unlikely, is just reality.
BTW – I’ve read many of your posts and find them generally to be insightful and informative. I just know what I see on this particular issue.
Chris Tomberlin
OutPost Pictures -
[Chris Tomberlin] “Again, respectfully, this is simply not the case. Have you ever actually done the test?”
Absolutely, on several occasions with DV, DVCAM and DVCPro material.
[Chris Tomberlin] “Consider this – when you put a DV25 tape in a deck that has an SDI output, is the deck not doing a hardware conversion from the DV codec to an uncompressed SDI stream? It IS.”
And that conversion is not magically adding any quality to the 5:1 compressed footage. It is simply converting it over to another format, such as what I can do directly with the Kona 2. Whether you capture DV or SDI, the footage is still 5:1 compressed and SDI is not going to change that.
[Chris Tomberlin] “Now I know theoretically the act of modifying those ones and zeros in any way is normally considered bad, but the effect of converting the DV25 footage to an uncompressed SDI stream via hardware in my deck has a visable and pleasing effect. It does look better than DV25 captured via firewire”
That’s simply a subjective statement. To you the footage looks better, to me I see no difference.
[Chris Tomberlin] “Do the comparison, blow up both captures in AE to %400 and look at something red. You’ll see a difference. Sometimes reality, no matter how unlikely, is just reality.”
If I have to blow something upu 400% to see a difference, that means that the naked eye can’t see the difference at 100%. Better test, do a split screen of DV vs. the SDI captured footage. That’s the test I do here. If I can see the split, then something is different between the two. If I can’t, then the images are identical.
You can work however you choose, but capturing DV25 via Firewire or SDI are one and the same which was the original question. Not DV25 vs. Uncompressed SD which is a completely different matter and which seems to be what you’re discussing. You don’t even need SDI to capture DV25 as Uncompressed, I used to do that 4 years ago with my CineWave system.
Walter Biscardi, Jr.
https://www.biscardicreative.comDirector, “The Rough Cut”
https://www.theroughcutmovie.comNow Posting “Good Eats” in HD for the Food Network
“I reject your reality and substitute my own!” – Adam Savage, Mythbusters
-
[walter biscardi] “And that conversion is not magically adding any quality to the 5:1 compressed footage.”
Ahh, but I have the optional “magically add additional chroma information and resolution” board installed in my deck. Pricey, but worth it 😉
Seriously, I know that nothing is being added to the 5:1 compressed DV footage, and I know that it is a common misconception that converting DV to an uncompressed format “gives you back” something that was lost in the compression in the first place. That’s not what I am saying here. I think what is happening is that the deck in converting to SDI is employing some chroma filtering or something that the Quicktime conversion in the Mac is not.
[walter biscardi] “If I have to blow something upu 400% to see a difference, that means that the naked eye can’t see the difference at 100%.”
[walter biscardi] “If I can see the split, then something is different between the two. If I can’t, then the images are identical.”Your point is well taken, but there is a difference between “looks” the same and “is” the same. You are saying that to you, the two approaches “look” the same. Fair enough. However, they technically can’t “be” the same.
[walter biscardi] “You can work however you choose, but capturing DV25 via Firewire or SDI are one and the same which was the original question. Not DV25 vs. Uncompressed SD which is a completely different matter and which seems to be what you’re discussing.”
True, I’m talking about the difference between loading DV footage via firewire versus loading the same footage to an uncompressed codec via SDI. If you’re comparing loading DV footage via firewire versus loading the same footage back to the DV codec via SDI, then we are talking about different things. Even then though, those two approaches would yield captures that are not “identical”. They would “look” much more alike though.
[walter biscardi] “You don’t even need SDI to capture DV25 as Uncompressed, I used to do that 4 years ago with my CineWave system.”
What exactly do you mean here? Are you talking about capturing something via firewire then playing it out with an uncompressed codec to an analog component output or something?
Chris Tomberlin
OutPost Pictures -
The full answer is here:
https://www.nattress.com/Chroma_Investigation/chromasampling.htm
in my white paper on the subject. I think it answers all your questions.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
-
Capturing DV over SDI doesn’t make it hold up better for colour correction compared to placing DV in a SD Uncompressed timeline. Only difference is the smoothness or not of the chroma – the quality of the chroma, hence dictating applicability for good CC is not altered.
DV or SDI – it’s a workflow choice, not a quality choice.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
-
Your engineer made an incorrect dub from DV to BetaSP. If the DV deck does not add setup, there are two solutions. One is to use a proc amp, the other is to playback direct from the DV, it being a superior format.
Also, read this paper on video levels, perhaps sending a copy to your engineer?
https://www.kenstone.net/fcp_homepage/video_levels_nattress.html
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
-
Thanks, Graeme!!
I’ll email that link to him, hopefully it will alleviate this year’s issues!
You ROCK!!
debe
-
Graeme
So to summarise:you can get most of the benefit of improved chroma smoothing by applying the FCP filters to FW captured footage and there’s no need to go to the expense of SDI out board for my DSR 1500 and a SDI capable FCP card?
Thanks
Andy
-
[Graeme Nattress] “Capturing DV over SDI doesn’t make it hold up better for colour correction compared to placing DV in a SD Uncompressed timeline. Only difference is the smoothness or not of the chroma – the quality of the chroma, hence dictating applicability for good CC is not altered.
DV or SDI – it’s a workflow choice, not a quality choice.”
That’s pretty much it in a nutshell.
Walter Biscardi, Jr.
https://www.biscardicreative.comDirector, “The Rough Cut”
https://www.theroughcutmovie.comNow Posting “Good Eats” in HD for the Food Network
“I reject your reality and substitute my own!” – Adam Savage, Mythbusters
-
Yes, but obviously with a render hit. That’s why I say it’s a workflow issue.
If you’re mastering back to DV though, you’ll loose not just the chroma advantage, but you’ll actually get worse quality if you smooth chroma without it actually being necessary.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
Reply to this Discussion! Login or Sign Up