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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 July 27th, 2006, 12:43 PM   #1
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Swapping G1 tapes on A1 Cam for HD-SDI Out

Asuming I have both models, will it be possible then to playback A1 tapes in the G1 cam? Referring to the HD-SDI Out. This way when buying multiple cams you could invest less with more A1's and only one G1 for playback.... is it possible?

Alexis
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Old July 27th, 2006, 12:48 PM   #2
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Frankly I see absolutely no reason why this wouldn't work. Thanks for bringing it up,
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Old July 27th, 2006, 12:58 PM   #3
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Doesn't that just convert HDV footage into a much bigger file that eats up bandwidth and HD space while retaining any of the artifacts of the original HDV? How's that better than downloading through firewire and upconverting on the computer?
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Old July 27th, 2006, 01:22 PM   #4
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Because it is in many ways easier to capture as DVCPRO HD on a mac and edit that way. You will get a lot more realtime performance this way. The quality may not be any better but it isn't really any worse either but a frame based codec is much easier to work with. Plus with a lot of color correction it might be better to capture as uncompressed because multi generational work will hold up better than if you tried to do it with mpeg-2. Every time you re-render the mpeg-2 you will loose quality. By the time the project gets finished the mpeg-2 could really suffer. Uncompressed or other great codecs allow you to stay in a high quality format and not really loose any more quality until the final output stage.
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Old July 27th, 2006, 04:17 PM   #5
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Thanks guys for the answers.

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Old July 27th, 2006, 04:59 PM   #6
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Someone please correct me if I'm wrong, but I believe the point of the HD-SDI out is to record the signal BEFORE it is compressed as HDV to tape. A $3000 difference would not be justified if the HD-SDI simply "decompressed" HDV.

What am I missing here?
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Old July 27th, 2006, 05:32 PM   #7
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Many of us like to get out of the HDV world as soon as possible. With the H1, I capture to tape using HDV, but immediately come out via HD SDI and capture the footage to Final Cut Pro using the DVC Pro HD codec.

I think getting just one of the higher end cameras makes sense.

Hope we soon see a deck that will support 24f and all of this need for capturing from the camera will go away.
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Old July 27th, 2006, 07:28 PM   #8
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Steve's question above is ..."How's that better than downloading through firewire and upconverting on the computer?"... I'm wondering the same thing. I import HDV footage as AIC via firewire. I edit using AIC, export to whatever is appropriate. The only time it is HDV is on the tape. If I've paid for the system capacity to capture a 4:2:2 signal via HD-SDI , why go HDV to tape at all (besides backup or distance)?

What are the benefits of capturing HDV footage via the HD-SDI out instead of using firewire?

I would guess that most people will not use these new cameras to record in studios. For them, is the extra cost of HD-SDI justified by an improved import of HDV material? Or should Alexis just save his $3000 and put it towards one more A1?
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Old July 27th, 2006, 08:25 PM   #9
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the HD-SDI is pulled from the signal before compressors. Thats what HD-SDI is, uncompressed HD.

If you want to go from an HDV source to HD-SDI, I would recommend getting Miranda's HDV Bridge.
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Old July 28th, 2006, 12:10 AM   #10
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Quote:
Originally Posted by Tom Vandas

What are the benefits of capturing HDV footage via the HD-SDI out instead of using firewire?
Just a way to convert your footage via a very clean signal path to another codec...like DVCProHD. This gets your footage out of the world of MPG2 based GOP frames and back into individual frames. Easier on the computer, not that much more space, better for rendering/graphics, etc.
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Old July 28th, 2006, 02:13 AM   #11
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Quote:
Originally Posted by Brian Critchlow
the HD-SDI is pulled from the signal before compressors. Thats what HD-SDI is, uncompressed HD.
Brian, I know, that's my point.

Quote:
Originally Posted by Kevin Wild
Just a way to convert your footage via a very clean signal path to another codec...like DVCProHD. This gets your footage out of the world of MPG2 based GOP frames and back into individual frames. Easier on the computer, not that much more space, better for rendering/graphics, etc.
Kevin, I already get that using firewire, to DVCPRO HD, AIC or whatever you want.

Do the benefits of importing via HD-SDI justify $3000 if that's all you use it for? I'm don't mean to be obtuse, I really want to know.
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Old July 28th, 2006, 08:07 AM   #12
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Alright, a few hours later and I'm feeling less cranky, and confident once again in my workflow. The thing that was freaking me out was that I could have been importing HDV content from tape via the HD-SDI and getting better results.

It appears to be debateable, no real answer. I did find one answer, however, that comforts me:

Quote:
(quoting from Larry Jordan's site http://www.larryjordan.biz/articles/lj_hdv_learn.html)

On the issue of whether converting from HDV to DVCPro HD is a good idea, opinions diverged. I respect Graeme too much to ignore his comments:

Graeme Nattress writes:

[Should you convert HDV to DVCPro HD?] No. Never! Why? Adding compression on top of compression is just bad. DVCproHD is way too compressed. It's full of artifacts even straight of a varicam. To add that compression on top of HDV just makes a mess.

Answer - edit HDV native - it's easy on a decent mac, and then just change the compression right at the end of editing to "uncompressed", do a final render before going out to master tape. Again, you'd never use HDV as a master - even one compression back to HDV looks awful.

Only use DVCproHD if that's what you shot, or are going back to DVCProHD tape. If you're recording live from SDI, uncompressed HD, or PhotoJPEG 75%, are much superior.
I have always found Graeme's comments here very direct, helpful and knowledgeable. Now I have to rethink my practice of editing in AIC!
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Old July 28th, 2006, 05:35 PM   #13
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HD-SDI for MDV playback

"will it be possible then to playback A1 tapes in the G1 cam? Referring to the HD-SDI Out. This way when buying multiple cams you could invest less with more A1's and only one G1 for playback.... is it possible?"

The recorded material on HDV will be MPEG-2 encoded with 4:2:0 color sampling. This eliminates a major advantage of HD-SDI ( a 4:2:2 color sampling). Playing back through the HD-SDI after recording means the signal will have to be run through the camera's MPEG 2 decoder and re-sampled. Better to upload the digital signal via fire-wire and either edit in HDV mode or, if required, transcode using a high performance software package.

HD-SDI would have a significant benefit in any rapid motion shot or pan where the rapid frame to frame changes can overwhelm a single pass MPEG-2 encoder. For these shots, the HD-SDI could stream the video and time code to a suitable recorder.
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Old July 28th, 2006, 07:25 PM   #14
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Quote:
Originally Posted by Paul Matwiy
The recorded material on HDV will be MPEG-2 encoded with 4:2:0 color sampling. This eliminates a major advantage of HD-SDI ( a 4:2:2 color sampling).
I like what you say here, a major advantage, not the only advantage.

For HDV tape playback via HD-SDI you don't get a quality advantage, but their are workflow advantages.

Like mentioned before its easier to work in a native intraframe codec like DVCPROHD rather than an intermediate codec. You can get to both with similar quality, but which is faster.

HDV or 1394 = Playback at real time over firewire + time to recompress on computer
HDV over HD-SDI = Realtime capture and encoding

HD-SDI could have just saved you hours of encoding depending on your project size.

Or a fully uncompressed workflow would also save on quality losses where more FX driven projects would see more compression artifacts. Also DVCPROHD would likely also offer a small benefit in this area because the artifacts are uniform for the whole project so it should look similar.

I think its easy to jump to conclusion about stuff in regards to quality. But Grame Nattress proved on his site that DV over SDI looks like it has better colour reproduction because its smooths the UV channels. It provided enough of an improvement that he even wrote a FCP plugin that duplicated what it did for DV footage for changing it to 4:2:2 colourspace.

These cameras aren't released and I don't know how it processes, but it has to take the 4:2:0 colourspace to 4:2:2 and it might smooth UV channels as well. Makes the footage softer but a little more natural.
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Old July 28th, 2006, 08:06 PM   #15
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I would never argue with the uber-brains like Grahme or Adam Wilt...however, you have to ask what sacrifices might you make for your own personal workflow and comfort.

I would guess there are differences that might even be seen if you stay in HDV codec vs DVCProHD IF you A-B'd them. However, I just do not see the difference and therefore I know that most people won't. Therefore, I'm willing to give up that 1% to use the workflow that works best for me...which is not converting footage after I captured it. I'd rather bring it in and start editing it.

Besides, I'm using FCP and until it supports 24F, it won't even capture 24F footage. I had a tape with some 1080i and some 1080-24f footage. It just skips right over the 24f stuff. So, for now, it's and easy decision for me and it looks GREAT!
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