Help on XLH1 Footage Storage Space

[Chris Evans]

Would anyone know wether it is actually 1 gigabyte per second that tranfers from the XLH1 to the computer or is it actually a gigabyte per minute, i am not sure how it works.

Thanks

[Ron Pfister]

There are two important distinctions to make:

1.) What the camera writes to tape and makes available through the FireWire/IEEE 1394/iLink interface is HDV, which concurs with the DV bitstream specification of roughly 30 Mbps (Megabits per second), which amounts to 3.75 MBps (Megabytes per second), 225 MB per minute or about 13 GB per hour.

2.) What the uncompressed HD SDI port delivers is a 1.485 Gbps (Gigabits per second) datastream. That's 190 MB per second (!!!), 11.13 GB per minute or about 670 GB per hour.

You see that if you want to record uncompressed HD SDI you need very fast and very large drives. This is not practical (or necessary) for most situations. A 1:10 on-the-fly compression would still result in stellar image quality with a much more manageable volume of data.

HTH,

Ron

[Chris Evans]

Thanks for the detailed reply, that helps me understand much better, much appreciated.

So if i wanted to use it to record in High Defenition and transfer it onto a computer, could i compress it and still be able to Chroma key fairly well.

Thanks again!

[Ron Pfister]

I haven't done that, and thus don't know from my own experience. With HD SDI I don't see problems, but you need a capture card that can encode on-the-fly or a serious RAID storage solution if you want to work uncompressed.

With HDV it could work, but I don't know how much the reduced chroma sub-sampling would produce edge artefacts compared to HD SDI. Maybe someone else could chime in?

Cheers,

Ron

[Chris Evans]

Thanks again for the quick reply. So really i could not edit in high defenition on my laptop. I do have a powerful desktop but would you not reccommend it.

Thanks

[Ron Pfister]

With HDV no problem. Finding a capture solution for a laptop that can convert HD SDI will be tricky, but I don't think it's impossible. If the next gen of AJA io FireWire interfaces are capable of transcoding in the device itself, that would do, for example. We'll have to see...

Cheers,

Ron

[Chris Evans]

If i did have an XLH1 would i still be able to make films at a fairly low storage size like 50GB - 80GB an hour on an external storage drive and still get a film look from the XLH1 at fairly high quality. Either in DV mode or High Defenition either way to get the film look.

Thanks

[Chris Hurd]

Hi Chris, it's important to understand that neither the storage size nor the format choice have all that much to do with getting a "film look." That has more to do with frame rate, lighting and other factors of production and postproduction. We have an entire forum dedicated to this topic, so you might want to search or browse through there to get an idea of what's involved:

http://www.dvinfo.net/conf/forumdisplay.php?f=34

[Chris Evans]

Thanks for your help, much appreciated