Advantage to SDI capture? was: Couple of questions at DVinfo.net

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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old October 16th, 2006, 10:06 AM   #1
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Advantage to SDI capture? was: Couple of questions

Hey guys, I can't seem to find answers to a couple of probably easy questions.

1. Does the A1 have XLR inputs?
2. What size is the front of the lens?
3. Correct me if I'm wrong but the only way to take advantage of the HD-SDI (and 4:2:2 sampling) is to be plugged into a computer with HD-SDI and recording directly to disk.
4. No over/undercranking?

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Old October 16th, 2006, 10:23 AM   #2
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I think most of the answers are here

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Old October 16th, 2006, 10:52 AM   #3
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Quote:
Originally Posted by Gene Crucean
the only way to take advantage of the HD-SDI (and 4:2:2 sampling) is to be plugged into a computer with HD-SDI and recording directly to disk.
Incorrect. That's not the only way to take advantage of HD-SDI. You can also use HD-SDI ouput to feed a separate VTR for recording in another HD format, such as HDCAM, DVCPRO HD, HDCAM SR, etc.
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Old October 16th, 2006, 11:10 AM   #4
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Quote:
Originally Posted by Gene Crucean
the only way to take advantage of the HD-SDI (and 4:2:2 sampling) is to be plugged into a computer with HD-SDI and recording directly to disk.
How? Is there now any HD-SDI interface for its use with a laptop?

Last edited by Mathieu Kassovitz; October 16th, 2006 at 08:13 PM.
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Old October 16th, 2006, 11:13 AM   #5
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Thanks guys.

Chris, I should have been clearer. I do a lot of shooting in the field which means that I almost have to shoot to tape which will be HDV. So what I was getting at is after recording to tape... is there any way to take advantage of the increased color sampling? I still think not.

Just in case anyone else was wondering what the answers were to my quesions without digging.

1. YES
2. Filter size is 72mm
3.
4. Negative
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Old October 16th, 2006, 11:22 AM   #6
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Supposedly -- and I have not been able to confirm this myself, but -- according to Scott Billups and several others, there is said to be a significant advantage to SDI capture from HDV playback. In other words, capturing a tape recorded in HDV from the SDI output is reported by Billups and other folks to be superior to capturing from the FireWire output. I'd love to see some hard data on this claim. It's the sort of test that would be excellent to show on this site.
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Old October 16th, 2006, 01:28 PM   #7
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Advantage to SDI capture

The two advantages to recording from the HD-SDI output would be to avoid the MPEG-2 motion artifacts and to record in a 4:2:2 color space as opposed to the HDV color space of 4:2:0. DH-SDI transfers from recordings already made to tape would not necessary reflect those advantages. Better to use an intermediate codec with 4:2:2 up-sampling after capture.
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Old October 16th, 2006, 01:39 PM   #8
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Capturing HDV tapes through SDI can make for easier editing. Well this is the case at least if you have a very fast raid. Uncompressed HD or DVCPRO HD can edit very fast on a moderate system. Much faster than what HDV can do. You will get more realtime and a better response by editing video this way. For years a lot of people have shot with highend DV cameras but edited using a system like the Video Toaster from Newtek which was an uncompressed SD system. They did this for a few reasons.

1. Editing was faster.
2. Higher quality for compositing and effects work.
3. better multigeneration quality.
4. Many claim the video actually looked a little bit better.
5. Better control with the other SDI based equipment they had.

In the case of HDV on the PC side the files are mpeg2 files which may or may not work very well in some 3rd party applications. Capturing to a AVI file means universal support to use that video file in any program you want.

The problem with compressed formats is that every time you do something it gets compressed even more. If you had to work with a HDV file across many different platforms and 3rd party tools you would quickly loose quality. By capturing as uncompressed even though the source was compressed you make sure it doesn't get any worse while you are editing. It will always stay at the same level of quality until the very end when you compress to whatever format you wish to compress to.

Capturing HDV through SDI is almost the same as using a codec such as Cineform. With Cineform you capture through firewire but the video gets converted to a format that this easier to edit and closer to a uncompressed format in terms of no generation loss. With SDI you are letting the camera do the conversion to an uncompressed source and then send that to the computer to save as a new file. In the end the results would be pretty much the same with SDI having the bonus of really high quality during live capturing directly to the computer. Cineform would always be limited to trying to upconvert HDV to a higher quality format.

So therefore there are advantages to using SDI even if you record to HDV tape. The advantages may not be as big as they are with live video but all of the workflow and generation loss advantages are still the same.
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Old October 16th, 2006, 01:44 PM   #9
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Quote:
Originally Posted by Paul Matwiy
The two advantages to recording from the HD-SDI output would be to avoid the MPEG-2 motion artifacts and to record in a 4:2:2 color space as opposed to the HDV color space of 4:2:0. DH-SDI transfers from recordings already made to tape would not necessary reflect those advantages. Better to use an intermediate codec with 4:2:2 up-sampling after capture.
But this was kind of my point. Since you record to tape in HDV (which is 4:2:0), doesn't that kind of defeat the purpose of outputting and capturing at a 4:2:2? Kind of like shooting in SD and uprezzing to HD.

Chris, that would be awesome to see some data on that. It's hard for me to justify a 3k price jump for HD-SDI when it's next to useless for me.
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Old October 16th, 2006, 01:48 PM   #10
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Thanks for the info Thomas. All good points.
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Old October 16th, 2006, 06:11 PM   #11
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Gene,

I have captured Canon HDV (1080i and F modes) to FCP in a variety of formats via SDI and a Kona LH card, and I can tell you from my own experiences that you really don't gain any quality transcoding to another compressed format, even to the best intermediate codecs like CineForm.

What you do gain is milder compression when recompressing material on a timeline by filtering, adding FX etc.

The new 24F support in FCP is excellent, and I've found the performance to be quite snappy for most common editing operations. (I have an older G5 dual 2.7)

The issue of timeline performance is really negligible IMHO. I get quite a few RT effects even on an HDV timeline, (the Kona card may be helping somewhat)...but guess what? More often than not I don't finish in HDV. I copy my HDV-edited sequences to Sheer lossless codec timelines (or standard uncompressed HD) and render in a much milder compression environment, and then compress for DVD or HD h.264 from a lossless HD QT file. The quality holds up quite well this way, and if I want to I can output HDV sequences back to tape also.

The nice thing about native HDV editing in FCP is not having to create clips 3-4 times the size of the original material.

In my opinion the only reason to use SDI now is for actual uncompressed capture of camera-head-live signal true 4:2:2 output from these cameras tethered to an appropriate recording device. (NLE/computer, Wafian, or HDCAM/DV100 decks, etc.)

SDI cards do potentially offer nice NLE monitoring output too.
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Old October 16th, 2006, 06:51 PM   #12
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So the conclusion is that the SDI output is not worth the $3000 extra for most of us? I rarely expect to capture live footage. I am not sure, but to capture uncompressed one would need a fast computer or harddisk with you in the field? Or can you still output to tape and capture through SDI?
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Old October 16th, 2006, 07:15 PM   #13
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Yes you can simultaneously record HDV to tape and output raw HD via SDI, but remember you get more than just SDI for the extra $3000. There's also TimeCode input or output, and Genlock... for some folks, these extra features together with SDI are indeed worth the extra money.
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Old October 16th, 2006, 07:28 PM   #14
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Quote:
Originally Posted by Floris van Eck
So the conclusion is that the SDI output is not worth the $3000 extra for most of us? I rarely expect to capture live footage. I am not sure, but to capture uncompressed one would need a fast computer or harddisk with you in the field? Or can you still output to tape and capture through SDI?
That is not true at all. A lot of people assume SDI equals uncompressed only but that is not true. The SDI itself is uncompressed but it is only a signal. If you do not want to deal with the expensive hard drives you can use DVCPROHD or photojpeg which will capture to a single everyday hard drive. Now you are only looking at $995.00 for the SDI card and around $250.00 for a good size single hard drive to capture to these compressed formats. DVCPROHD may not be as good as uncompressed in terms of raw quality but it makes up for it with raw editing speed. Photojpeg at 75% or above can look better than DVCPROHD and pretty darn close to uncompressed but may be slower to edit and if I can remember the realtime effects in FCP will not work.
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Old October 17th, 2006, 03:27 AM   #15
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I am still not sure if I could use SDI. First of all, will SDI work only with live recording? Or can I output through SDI and record to my computer from tape when the footage was already record on tape?

Is there any other way to record uncompressed footage, let's say firewire?

I understand that the editing of uncompressed footage is faster, but what about the required storage space, is it also x times higher?

The genlock and timecode outputs are only useful for multi camera shooting, or also if you use only one camera for 100% of your work?

I hope you can clarify this.
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