SDI - Why do I need it?

[Miguel Lombana]

Ok I really hate to show my ignorance here, but other than knowing what SDI stands for, in consideration of an upgrade to HD, why is it important to me? I see references to it all the time but have been scared to ask until now so anyone?

My goal BTW, is to add the H1 to my arsenal and use it in SD for a while until an HD customer that understands they will only be able to playback their production (wedding or event) on a PC. I'm ready to edit HD according to the plug-in's that I have for Premier 1.51 so now it comes down to the main differences, hence my wanting to know more about HD-SDI.

Thanks and please go easy on me.
MIGUEL

[Peter Ferling]

Simple. If you wish to do some compositing and special effects work, and want 4:2:2 colorspace, you'll capture via SDI. (I'm not sure if it's 8 or 10bit either. We'll have to see).

You want to use the H1 for SD work? Have you considered that the audio is only mpeg layer II? (Unless your capturing audio via an external recorder, no problem).

You'll also be working with uncompressed video, and will need a large disk array and SDI interace face. You'll also have to factor in an external tape deck to archive your high quality media, and keep it in the 4:2:2 colorspace.

Unless you find a deal on ebay, it's a jump of about $30K US to your existing workstation (not including the camera).

Renting a deck, or having a local shop that can transfer to tape will save a few bucks. While on the subject, why not just rent the equipment, including the H1 when needed? Folks are paying for your expertise, so the cost of ownership can be, well, costly.

[Kevin Shaw]

Originally Posted by Miguel Lombana

My goal BTW, is to add the H1 to my arsenal and use it in SD for a while until an HD customer that understands they will only be able to playback their production (wedding or event) on a PC.

You can deliver HD resolution to customers now using the Windows Media format on standard red-laser DVDs, with playback on the Avel Linkplayer2 which costs $249. And if you're booking weddings now for next summer, proper blue-laser HD DVD players should be shipping by the time those videos are edited.

Also note that HD-SDI options are overkill for typical wedding videos, and would only be something to consider if you had a client who wanted the "best of the best" and was willing to pay a whole lot of money to get it. See elsewhere in these forums for a description of the "Wafian" HD-SDI recorder, or you could hook a cable to a computer with an HD-SDI capture card and grab 4:2:2 video that way. But for a wedding video or other event work? Nah. Standard HDV source should be plenty good enough for most event videos for the next few years.

[Kevin Shaw]

Originally Posted by Peter Ferling

Uness you find a deal on ebay, it's a jump of about $30K US to your existing workstation (not including the camera).

With recent advances in SATA hard drive technology, you could build an HD-SDI capture setup for as little as $5-6K, depending on what codec you plan to use and how much video you need to capture. Eight good 250-300 GB hard drives will run you about $1000, and high-end SATA RAID controllers are only a few hundred more. Add the basic components for a computer, an HD-SDI capture card and some compatible software, and you're good to go.

[Christopher Glaeser]

"Eight good 250-300 GB hard drives will run you about $1000, and high-end SATA RAID controllers are only a few hundred more."

Does HD need 8 SATA drives, or is 4 sufficient? I've been thinking about adding an external SATA RAID box to my system using a card, external SATA box, and four SATA drives.

[Miguel Lombana]

Originally Posted by Peter Ferling

Simple. If you wish to do some compositing and special effects work, and want 4:2:2 colorspace, you'll capture via SDI. (I'm not sure if it's 8 or 10bit either. We'll have to see).

You want to use the H1 for SD work? Have you considered that the audio is only mpeg layer II? (Unless your capturing audio via an external recorder, no problem).

You'll also be working with uncompressed video, and will need a large disk array and SDI interace face. You'll also have to factor in an external tape deck to archive your high quality media, and keep it in the 4:2:2 colorspace.

Unless you find a deal on ebay, it's a jump of about $30K US to your existing workstation (not including the camera).

Renting a deck, or having a local shop that can transfer to tape will save a few bucks. While on the subject, why not just rent the equipment, including the H1 when needed? Folks are paying for your expertise, so the cost of ownership can be, well, costly.

Ok Peter so to understand, SDI is not something that is "typical" for the casual shooter / editor. If I were a high end production house then it is something that I would have already planned for, but in my situation, the output of the H1 to my PC via 1394 and PPro 1.51 is going to have me editing and producing HD content. Am I understanding this correctly.

As for drive arrays, I have a new Dell 670 on order right now shipping with 2 500g drives in a RAID 0 with room for 2 more so I'm hoping that 1tb is more than enough to do a couple of hours of 1 HD cam and 1 SD cam editing in a project.

Thanks so far.
ML

[Hans Damkoehler]

Originally Posted by Peter Ferling

Simple. If you wish to do some compositing and special effects work, and want 4:2:2 colorspace, you'll capture via SDI.

Just trying to clarify here ... HDV records to a 4:2:0 colorspace. So, to get 4:2:2 you must bypass recording to tape and record out to a deck through SDI ... right?

Will it "rez up" from 4:2:0? How can it replace what is already missing?

I'm talking a little over my head here but I think I have point ... :o)

[Pete Bauer]

Let me take a stab at it and those with more technical knowledge can add or correct.

4:2:2 uncompressed 1080i60 (in NTSC-land anyway) comes off the CCD block; after magical and secret DIGICII processing it can be recorded on tape in HDV at 4:2:0 with 1080i60 (with or without 3:2 pull-down for 24F or "progressive segmented frame" for 30F) using MPEG-2 compression and it can also be output via HD-SDI at 4:2:2 uncompressed 1080i60, 1080F24, or 1080F30 at 1.485 gb/sec.

Ok, it is confusing!

[Barry Green]

The data is handled at 4:2:2 internally. It is the HDV compression that performs the chroma decimation to 4:2:0. If you bypass HDV compression and put the internal signal right onto the HD-SDI output port, it will still be at 4:2:2.

[Chris Hurd]

Originally Posted by Peter Ferling

You want to use the H1 for SD work? Have you considered that the audio is only mpeg layer II?

When recording in SD mode, the H1 audio is *not* Mpeg at all.

[Hans Damkoehler]

Great info ... thanks, Barry & Pete.

So, in reference to Miguel's original question, the SDI is geared towards:

- External recording on to achieve a 4:2:2 colorspace
- Monitoring, I guess
- Positioning the XL H1 as a viable HD studio option

For the weekend wedding/event videographer who is posting in HDV the SDI out feature may not be a standout feature ... true?

BTW ... this may be another thread ... but I've seen an XL1's transport system die prematurely due to the double use of recording then digitizing from the camera ... is there a deck that will playback Canon HDV and save the camera for shooting?

[Barry Green]

Originally Posted by Hans Damkoehler

For the weekend wedding/event videographer who is posting in HDV the SDI out feature may not be a standout feature ... true?

For the average wedding/event videographer, I doubt they'd find much if any value in the SDI port. Its main value will likely prove to be for studio applications, and a secondary level of value will be for those doing compositing/effects work who need access to uncompressed output (and have the necessary equipment on hand that can handle recording that output).

is there a deck that will playback Canon HDV and save the camera for shooting?

For 60i, the Sony deck should be compatible. For 24F and 30F, no.

[Bob Grant]

Certainly directly for us average guys the SDi feature isn't going to mean anything directly.
Indirectly it'll make a difference. The HD SDI output in combination with the genlock input makes this a viable camera for both OB and studio work. Given the high cost of the necesarry switchers etc a bit out of most peoples league however it does broaden the potential market for the camera without adding a large cost burden, smart thinking, a few ICs and connectors aren't expensive. As Canon have said the biggest cost in the camera is the lens which is how it should be, no matter how good the rest of it is it all starts with the lens.
One other feature that hasn't had much press is the full remote control capability of this camera, you can control all camera functions from a laptop. For those doing vanilla multicamera shoots this should be a godsend.
It should be mentioned also that not only does the SDI output give you 4:2:2, it bypasses the HDV compression, well depending on how you record from the SDI feed of course.

[Thomas Smet]

4 fast drives in a raid should work well for HD but only for a short time. You would never be able to fill up the drives and get the same bandwidth. With 4 drives you may only be able to capture uncompressed HD up till 50% full and then you might start to drop frames. a 8 drive array will sustain the datarate much better so you might be able to almost fill the drives and still have enough bandwidth for HD.

For cost reasons and uncompressed HD it might be better to build a 8 drive array with 8 80GB drives. This would only cost around $400 for the drives but give you a lot of super fast drive space. You may even have enough bandwidth to edit 2 streams of uncompressed HD in realtime. This does only give you 640 GB but remember you will be able to use the full 640 GB instead of just half if you were to use larger drives in a 4 drive setup. For most studio type work like music videos or TV commercials 640 GB would be more than enough space.

If the SDI port on the XLH1 is only 8bit which I think it is then using a product like Decklink you can capture 8bit uncompressed instead of 10bit which saves a lot of space and bandwidth.


Finally with a FCP/Decklink system you actually don't need to capture to uncompressed to use the SDI port. You could capture to DVCPRO HD which at 1080i from the XHL1 will look much better than 1080i HDV and it would also be 4:2:2 for FX work. DVCPRO HD can work off of a single SATA drive. This is a good midpoint between HDV and uncompressed HD. You can also capture to a lossless codec such as the Bitjazz codec with the Decklink cards. This will give you around a 2:1 compression rate bringing the bandwidth for HD way down. You may even be able to capture some HD on a empty 2 drive raid. A 4 drive raid will easily handle 8 bit Bitjazz HD. The only problem with the bitjazz codec is that it isn't a native FCP codec so all video would have to be converted in order to edit well in FCP. For mainly FX work done in Combustion or Shake this format would work great.

A note about DVCPRO HD. I personally like the 1080i version of DVCPRO HD much better. The 720p version only records 960x720 pixels compared to the 1280x720. This makes the video a little softer than HDV. The 1080i flavor however records 1280x1080 which is actually very close to HDV's 1440x1080. The PAL version of DVCPRO HD actually does use 1440x1080. At 1080 resolutions it is actually very hard to tell the difference between 1280 and 1440.

So you see just because the SDI port is uncompressed doesn't mean that is the only way it can be used. There are a lot of options that are not uncompressed but still give much higher quality than HDV.

[Kristian Indrehus]

Many like me will prefer to record the MPEG2 using portable drives like the firestore. No risk of dropouts, longer rec. times, start editing at once etc. If they make a portable drive that records say HDVC pro100 the SDI may provide a multi-format compatibal digital out.