Is the HD-SDI necessary?

[Robyne Hunwick]

I need to make a decision on whether to get another XH A1 or the XH G1 for its HD-SDI component. Is it true that the colors/pic will have less noise using the HD-SDI when outputting raw footage from cam to computer.

The way I have it now is that I will be shooting directly on to cartridge tape and capturing to computer later. Maybe Im still missing a few things or ideas with what the HD-SDI does... can it guarantee less picture noise when transferring cam to computer? Heck I don't even know if the HD-SDI does this (embarassing i know) how to use it, what it looks like, etc. I sort of feel like i know enough to be dangerous, as Im sure you'll agree. HELP.. please!! Anyway here are my specs:

Final product/end result will be composed in DVD in 16:9. The current cam i have is the XH A1. The computer I will be working on is similar to http://www.biwaymedia.com/system/Matrox.htm with a few extra gigs of ram and a few other options.

I am recording in HDV, shooting with 60i and plan on downgrading to SD in the editing process. Im not sure if I need to provide additional info (if so please ask... I really need to decide on the right purchase/setup) here but is this set up going to provide me the clarity i need to find with final product or will the HD-SDI give me better odds of losing less pixels etc????? Once again I sort of feel like i know enough to be dangerous, as Im sure you'll agree... and this stuff isnt cheap... I just need hindsight so i don't spend $$ frugally. HELP.. please!!

[Greg Boston]

HDSDI is a high speed data path and protocol for streaming audio/video. It runs at approximately 1.4 gigabits per second. Once you record to tape, the compression of the data has already occurred. Bringing it back out the HDSDI pipe can be done, but it is upsampling the data to fit the spec.

However, if you capture directly from the live signal through HDSDI, it is a conduit to the raw uncompressed video from the camera head and will have little or no compression and better color resolution. You have to have a dedicated capture board and high speed storage solution to take advantage of this though.

-gb-

[Robyne Hunwick]

After doing additional research regarding the HD-SDI ive come to recognize ive touched on a very complicated issue. I really had no clue... I'm a newbie and learning and taking this in rather quickly.

Pondering thoughts. "I just can't understand why the industry would leave us high and dry like this.. perhaps the technology is superseding on one end of the token yet minimizing/or cant keep up on the other side.... It almost seems easier to stay with SD.. but I wont.. however, there must be a better way. I may consider the aja xeo card, etc... but then we have specifics with computer issues... I certainly wont go with the colorcorrector(??) as Im not in that sort of position"

Is it true that even without accessing the HD-SDI output along with shooting in high def and capturing in SD will provide an overall better quality pic with less noise then whats found when shooting in SD. And if the overall product needs to be in DVD will consumers be able to watch in HDV... i thought i read somewhere consumers access to view this is limited. hmmmm this doesnt seem to be right.

Any thoughts... Im off to do some more reading

[Robyne Hunwick]

Originally Posted by Greg Boston

HDSDI is a high speed data path and protocol for streaming audio/video. It runs at approximately 1.4 gigabits per second. Once you record to tape, the compression of the data has already occurred. Bringing it back out the HDSDI pipe can be done, but it is upsampling the data to fit the spec.

However, if you capture directly from the live signal through HDSDI, it is a conduit to the raw uncompressed video from the camera head and will have little or no compression and better color resolution. You have to have a dedicated capture board and high speed storage solution to take advantage of this though.

-gb-

Thanks Greg.. your explanation is to the point and really easy to understand. If I may ask would the capture card be an external component? TIA

[Pete Bauer]

Hi Robyne,

You're quite right that you've touched on a complicated -- and relatively expensive -- issue. The dedicated SDI card that goes into one of your computer's PCIe slots and either the drive array to handle the gargantuan uncompressed data stream -- or intermediate codec software (such as Cineform Prospect) to allow capture to a simpler 2-drive RAID 0 in your computer -- will cost at least several thousand dollars more than just recording in HDV and capturing via 1394 ("firewire"), and would require you to shoot tethered to your computer.

What you gain for all that is perhaps very slightly higher luma picture detail and 4:2:2 chroma rather than HDV's 4:2:0. This is definitely advantageous if you intend to do a lot of keying or other complex processing in HD, but IMO very much overkill for SD final output. I think most folks would agree that editing HDV from tape will be more than adequate for an SD final product, even if there is keying work to be done.

My opinion is that if your final product is regular 16:9 DVD, save yourself the many thousands of dollars and complication. FWIW, I've been wanting to do HD SDI for keying/compositing HD projects with my H1's since Day 1, and haven't quite been willing to make that big leap to HD SDI. Maybe soon, though. ;-)