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Is a capture and playback device a passthrough or a pitstop?

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Frank Black
Is a capture and playback device a passthrough or a pitstop?
on Dec 23, 2011 at 4:02:57 am

Hi guys,

Two of you already know that I'm researching the depths of what a capture and playback device does WHAT but that I'm looking for "precise" answers in a language a 2nd grader -- me! -- would understand.

Anyway -- I've been going in circles for 2 and half weeks -- no lie. I have so much in notes -- in word, in notepad, on paper, in emails, IN MY HEAD -- that I need to be UNCOMPRESSED!

I feel like all the answers are in my notes (so many notes). But the dots aren't connecting, and part of the reason is that I'm getting opinions that seem to contradicting but in all probability are most like just not "sensitive" enough. The other part of the reason is that I'm a second grader!

The dots aren't connecting because there actually are "holes" in the lines at the beginning and end the dots are. These holes are cause by the two "parts" mentioned above. I'm stuck MAINLY on one thing! And I need an a "sensitive" answer!! -- not an industry answer! I need (and I say need respectfully) an answer sensitive the level of my mind's current capacity not to shut off the moment an unfamiliar term injects it with fear and doubt.

So here's where I'm stuck (and there's gotta be a simple way to FULLY explain this):

1. why do we say that a cap and play device transfers uncompressed when a camera compresses the data when recording it, and since the camera's decompression doesn't fully restore. a full answer if possible. i will remember your name forever. full meaning something like this (though this probably wrong): well, a camera compresses it, then a cap and play connects to it via sdi, a button is pressed and a camera begins playback, and another button is pressed, and the cap and play sucks the wind out of the sdi and the sdi vacuums the footage out of the camera's playback (yep, takes it right off the LCD), and then it takes the data, encodes it, and shoots it thru a thunderbolt pipe into a mac. oh ye and by the way -- the playback was uncompressed. we call it uncompressed because the playback just orders the lost data to come out where it has fled to and get back in line to form a full original file in all its megabytes, and the guys that aren't coming back -- well we won't even notice they're gone. and so and so. (sorry for getting carried away. thanks if you're still with me. help!)

2. when does the camera decompress -- in playback or when you press the magic "decompress" button.

3. how do aja Io, BM UltraStudio 3d, and MXO2 transfer? does it serve as a passthrough or a pitstop? does it say: hang on data! cant go to the mac yet! we must do something to you first. we must: encode? decode? x? y? z?...

4. do all of the three machines mentioned above capture from playback only?


thanks. i'm in debt to you already if you've read this far.


val


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David Roth Weiss
Re: Is a capture and playback device a passthrough or a pitstop?
on Dec 23, 2011 at 5:10:36 am

[Frank Black] "1. why do we say that a cap and play device transfers uncompressed when a camera compresses the data when recording it, and since the camera's decompression doesn't fully restore."

The camera does indeed compress the video signal. It has to in order to record to tape, as the bandwidth of tape will not accommodate the full bandwidth of an uncompressed video signal.

In layman's terms, "uncompressed" video in an I/O device (that's the proper name BTW) means no further compression of the signal, or in some cases "lossless," which essentially means you can't detect the loss.

[Frank Black] "2. when does the camera decompress -- in playback or when you press the magic "decompress" button."

Cameras don't decompress. The signal is compressed before it goes to tape or to a card (i.e. some info is discarded) and that info is gone for good. This is why some video formats are better than others. Some simply throw out less info. Some have exotic algorithms that just do a better job.

[Frank Black] "3. how do aja Io, BM UltraStudio 3d, and MXO2 transfer? does it serve as a passthrough or a pitstop? does it say: hang on data! cant go to the mac yet! we must do something to you first. we must: encode? decode? x? y? z?..."

That depends on whether you're capturing the video exactly as it was recorded, or if you're transcoding it to another format or codec. I/O devices can function like firewire and SDI, just passing the signal through, or they transcode (change) the signal to just about any other codec available on the system, and most can cross convert, down convert, and/or up-convert, all of which happens via hardware in realtime.

[Frank Black] "4. do all of the three machines mentioned above capture from playback only?"

Are you asking if live capture is possible? If so, I'm pretty sure all will do it, but you better test the device thoroughly before using it in the field.

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
http://www.drwfilms.com

Don't miss my new Creative Cow Podcast: Bringing "The Whale" to the Big Screen:
http://library.creativecow.net/weiss_roth_david/Podcast-Series-2-MikeParfit...

POST-PRODUCTION WITHOUT THE USUAL INSANITY ™


Creative COW contributing editor and a forum host of the Business & Marketing and Apple Final Cut Pro forums.


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Frank Black
Re: Is a capture and playback device a passthrough or a pitstop?
on Dec 28, 2011 at 1:25:56 am

David, please very seriously consider forgiving the very delayed response. It's just how things turned out, although I did read your response the day after you wrote it. And I finally understand! Instantly upon seeing the care you took with your response, I felt an appreciation for the many minutes you spend to help me. You were a big help to me before as well, in a Vegas vs. FCP question I asked a year or two or so back.

David, I actually understand. I won't lie -- I posted this question in about a dozen cow forums, and many folks took the time to help (!!), and so aside from understanding, I picked up a few gems from everyone who responded. I'm very thankful, and I am "uncompressed." Man, I really have been going in circles for about three weeks!! Thank you a lot, David.

Very best,
Val


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Frank Black
Re: Is a capture and playback device a passthrough or a pitstop?
on Dec 28, 2011 at 2:59:03 am

David, if you can find the time, and can keep helping, I have some more questions about my continuing research about I/O devices. If you can help even a little, that would be helpful, but if you can help me like you helped me with uncompressed, I would be so fulfilled. Please help if you can. Here's what I'm trying to find.

Ok -- so what is 3G-SDI/HDMI? So what if I have SDI? Big deal. Tougher cables, etc... But WHAT ELSE? What stands out? Can it possible transfer at higher quality? Can a cable really affect the actual quality of the footage?

Ok -- and how can t SDIs be used for dual-link 4:4:4 RGB I/O? (What is 444 RGB?)

And if I'm converting between 4:4:4 and 4:2:2 to set up single-link HD-SDI monitoring and output, what and why am I really doing? Where did the 444 come from and how and why did it become 422? Why not 429? Why not 329?

And what about conversion -- up/down/cross -- WHY and HOW? Do I choose this? Is there a button to press to choose one? And why would I need to do this? I know that in a broadcast setting, and I’m sure other settings as well, one may be given some SD footage and some HD and will need to kinda match them up. But why else?

And what happens in the actual conversion? Do more lines get created? Does color get added? (Remember though, just cause I know uncompressed doesn’t mean I graduated second grade already. And I’m still asking most hopefully).

And what is motion-adaptive conversion? By the way guys – I did look into this. I am having difficulty finding answers though. For motion-adaptive, I'm finding scientific answers; like not even film related. But I was able to get some kinda understanding. But for 4:4:4 and 4:2:2, I’m not finding anyone talking about its concept online. I just see definitions. If you can help, please do.


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David Roth Weiss
Re: Is a capture and playback device a passthrough or a pitstop?
on Dec 28, 2011 at 5:11:30 am

I'm way to tired to answer everything tonight. But, here's a start.

[Frank Black] "Ok -- so what is 3G-SDI/HDMI?"

3G SDI is the new and more powerful SDI standard, replacing dual-link SDI. Unless you're doing 3D movies you probably won't need it anytime soon.

HDMI is a very popular and easy single-cable pathway for both audio and video. It's now the choice of many to send video from the newer I/O devices to many pro & consumer monitors. It's a cheaper solution than SDI, because the cable is less expensive.

My Matrox MXO2 LE has both SDI and HDMI. I run HDMI to my client monitor and SDI to my broadcast monitor.

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
http://www.drwfilms.com

Don't miss my new Creative Cow Podcast: Bringing "The Whale" to the Big Screen:
http://library.creativecow.net/weiss_roth_david/Podcast-Series-2-MikeParfit...

POST-PRODUCTION WITHOUT THE USUAL INSANITY ™


Creative COW contributing editor and a forum host of the Business & Marketing and Apple Final Cut Pro forums.


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Frank Black
Re: Is a capture and playback device a passthrough or a pitstop?
on Dec 29, 2011 at 12:49:54 am

Thanks David --

[D.W.] 3G SDI is the new and more powerful SDI standard, replacing dual-link SDI.

Rookie question: does dual-link mean two SDI ins/outs? And if so, and 3G SDI replaces dual-link, then why do some I/O devices have 2 SDIs AND 3G?

Thx


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Frank Black
Re: Is a capture and playback device a passthrough or a pitstop?
on Dec 29, 2011 at 12:58:58 am

David, I think I'm gonna answer my own question -- so 3G can replace dual link SDI because it can take more bandwidth!!! (and I'm assuming here that dual link means two SDIs.)

And the reason therefore why some I/Os have two is for 3D capture?


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David Roth Weiss
Re: Is a capture and playback device a passthrough or a pitstop?
on Dec 28, 2011 at 4:35:53 am

You're very kind, and I'm happy to help you!

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los Angeles
http://www.drwfilms.com

Don't miss my new Creative Cow Podcast: Bringing "The Whale" to the Big Screen:
http://library.creativecow.net/weiss_roth_david/Podcast-Series-2-MikeParfit...

POST-PRODUCTION WITHOUT THE USUAL INSANITY ™


Creative COW contributing editor and a forum host of the Business & Marketing and Apple Final Cut Pro forums.


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