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General HD (720 / 1080) Acquisition
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Old August 21st, 2008, 09:58 AM   #46
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In addition to conversion time, I believe there is also an issue with image quality. If you de-compress a group of pictures (GOP) and then re-compress to new format that compresses each frame individually, then you've gone through another compression cycle. This will add to mosquito noise and blocking artifacts. Two compression cycles (one for capture, and another for authoring edited output) is already too much, and it usually shows. The only case where it doesn't show is if the capture format is wavelet (i.e. Red 1, SI-2K), or the DCT capture compression is really light (i.e. higher bit rate formats).

You could de-compress a GOP based format like SxS and then create uncompressed files for editing, but the data size on the hard drive would be huge and this would slow down the editing as well.

From what I understand, it's generally best to edit in the format you use to capture, otherwise you will lose quality or speed.
Cineform works well.
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Old August 21st, 2008, 10:07 AM   #47
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Cineform works well.
Yes. Cineform uses wavelet compression, so it can be used as an intermediate without any noticeable loss in quality.

But from what I've heard, Cineform software costs more than most editors. Around $2000 if I remember correctly.
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Old August 21st, 2008, 10:11 AM   #48
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You could de-compress a GOP based format like SxS and then create uncompressed files for editing, but the data size on the hard drive would be huge and this would slow down the editing as well.
Typical editing intermediates use about the same bandwidth and storage as DVCProHD in some cases (e.g. Cineform, Canopus HQ) or somewhat more in others (Avid DNxHD, Apple ProRes), but not nearly as much as uncompressed footage. With hard drives so cheap these days decompressing for editing isn't a problem, and performance is improved significantly (not decreased) in the process.

In theory an extra transcoding step will reduce image quality slightly, but it's doubtful the results would be noticeable to most viewers. If you're really concerned about image purity you're arguably better off with a GOP-based recording format, because that can be delivered directly to viewers via Blu-ray or the internet where DVCProHD has to be transcoded for viewing purposes. In practice all the popular HD recording formats are good enough for most purposes, even DVCProHD. ;-)
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Old August 21st, 2008, 10:26 AM   #49
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If you're really concerned about image purity you're arguably better off with a GOP-based recording format, because that can be delivered directly to viewers via Blu-ray or the internet where DVCProHD has to be transcoded for viewing purposes.
This is true if you are not doing any editing. When you edit, your edit points will generally be within the GOP, so the video will have to be decompressed and then recompressed. As far as I know, all editors do this internally when authoring output.
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Old August 21st, 2008, 10:30 AM   #50
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With hard drives so cheap these days decompressing for editing isn't a problem, and performance is improved significantly (not decreased) in the process.
Uncompressed 1080p video is huge. Moving that much data through the editor will slow things down. With uncompressed footage, it's not the processing intensity, but rather the I/O intensity that slows things down.

To add some dimesions to this, let's say you're doing a 2-hour feature and your shooting ratio is about 10:1. That's 20 hours of raw video. Uncompressed 1080p video is just over 300GB per hour, so that would be over 6 Terabyes for just the raw video.
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Old August 21st, 2008, 10:40 AM   #51
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Uncompressed 1080p video is huge. Moving that much data through the editor will slow things down. With uncompressed footage, it's not the processing intensity, but rather the I/O intensity that slows things down.
That's what RAID arrays are for.
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Old August 21st, 2008, 10:43 AM   #52
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To add some dimesions to this, let's say you're doing a 2-hour feature and your shooting ratio is about 10:1. That's 20 hours of raw video. Uncompressed 1080p video is just over 300GB per hour, so that would be over 6 Terabyes for just the raw video.
At today's prices, that's well under $1k in hard drives (but using something like Lagarith can make a lot of sense - if you want a completely lossless intermediate).
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Old August 21st, 2008, 10:44 AM   #53
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This is true if you are not doing any editing. When you edit, your edit points will generally be within the GOP, so the video will have to be decompressed and then recompressed. As far as I know, all editors do this internally when authoring output.
That's one reason it pays to convert to an I-frame intermediary. However, you can take raw GOP-based video and deliver it directly to end viewers, something you can't realistically do with DVCProHD. With any video format you're going to end up converting somewhere in the process unless you deliver the raw footage.

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Uncompressed 1080p video is huge. Moving that much data through the editor will slow things down. With uncompressed footage, it's not the processing intensity, but rather the I/O intensity that slows things down.
Please read my preceding comments again: I'm not talking about uncompressed video. Digital intermediates use ~80-160 Mbps and work very well for editing GOP-based source video on today's computers: I can handle 3 layers of HD 1080i on my laptop from an external bus-powered hard drive - and the codec for this comes free with Edius. It doesn't sound like you're familiar with how all this works, so I'd suggest you study up if you want to comment further.

Last edited by Kevin Shaw; August 21st, 2008 at 10:46 AM. Reason: clarification
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Old August 21st, 2008, 10:50 AM   #54
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Yes. Cineform uses wavelet compression, so it can be used as an intermediate without any noticeable loss in quality.

But from what I've heard, Cineform software costs more than most editors. Around $2000 if I remember correctly.
Actually, the standard version of cineform which can handle anything up to 1080p is only $699.

Higher versions which can handle up to 4k at 10-12bit are more expensive, but I don't think any of them run as high as $2k.
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Old August 21st, 2008, 11:19 AM   #55
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The big advantage to wavelet compression is speed. Similar quality (at a given bitrate) can be achieved with DCT like compression (like AVC Intra), but it is slower to encode and decode.

Cineform NEO HDV, which is quite adequate for many purposes, is only $250. The only thing I really dislike about Cineform is how over the top they are about limiting you to using their products on only one computer per licensed copy.
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Old August 23rd, 2008, 01:52 AM   #56
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I think you will find Cineform will readily agree to having one copy simultaneously installed on 2 machines. At least that has been my experience with AspectHD.
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Old August 23rd, 2008, 08:41 PM   #57
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My experience has also been that the folks at Cineform are completely reasonable about having one copy on their notebook and one on their main machine. Or whatever else you need, within reason.

Just ask them for what you need and I think you'll be pleasantly surprised at how helpful they are.
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