What kind of data-rate does XDCAM require?
 

In our present SD workflow, we use Firewire 800 G-RAIDS as our main media drives. They work great for anything up to two streams of 8-bit uncompressed SD. Will these drives be fast enough to work with XDCAM?

I guess my real question is....does the highest quality of XDCAM record at 35 Mb/s, or 35 MB/s? The Firewire will be fast enough for mega bits, but not for mega bites.

You don't transfer the 35mb via FW in a streaming mode. It's done using FAM...file access mode. The camera (or deck) shows up as any other disc drive on your computer and you copy the files to your system. This makes it a faster than real time ingest.

-gb-

But Greg, once you copy the files.....
 

....to your system, then you have to edit with them. We use Final Cut Pro as our editor. My question is, will a Firewire 800 drive (like a G-RAID) be fast enough to edit multiple streams of XDCAM video? If not Firewire, then what about an eSATA RAID?

For multiple streams, you might need firewire 800. eSATA would be even better, RAID or non-RAID. Sorry I mis-understood your original inquiry.

-gb-

1 megabyte = 8 megabits

35 megabits/sec = 4.375 megabytes/second

for xdcam hd ,
if you use avid media composer you need something better than firewire 800 raid 0 drives , you need scsi ultra 320 , 2 drives or more in raid setup .
it's the same for edius broadcast .
of course the firewire 800 or sata 150 is enought to play 2 or 3 videos in 35MB/s in real time , the problem is when you make some effects , or transitions . to be non destructive the editing software calculate the effects in hd codecs that is between 180 to 280 MB/s it depend of the settings in the softwares . canopus HQ variable bitrate for edius and Avid DNxHD for media composer .
then if you dont have drives that can read this in real time , your video will stop or flash .

Avid MC works absolutely fine with good firewire 800 drives or better still sata raid. DNxHD data rates are a third of uncompressed HD rates. A properly set up sata raid array can easily handle uncompressed 10bit HD. I know, its what I have been using for 3 years. If your using FCP you should be fine with firewire 800. Get FCS2 and you can use the new Prores codec for renders and grading.

Yes. They will be plenty fast enough.

It is 35 Mb/s (mega bits). Even a normal firewire (400) drive can handle this format with ease. Your G-RAID operating at FW800 should certainly have no trouble at all.

Note: If you have any FW400 devices plugged in to your Mac's built-in firewire ports, or daisy to your G-RAID, then your all your firewire speeds, including the G-RAID, will be throtled back to FW400. This includes plugging in your XDCAM camera or deck.

In my experience, one should not look only at the data rate. XDCAM HD uses MPEG-2 compression and because of the GOP factor both, the CPU and the drives endure more stress. For exemple, XDCAM HD at 25mbps does not edit nearly as smoothly as DV25 even if the files size are nearly identical. The Firewire 800 G-Raids are okay but can fall behind when dealing with more than two or three layers of XDCAM HD material.

My 2 cents.

Thierry.

I've worked with 35mbs material on a 1st gen Mac Pro, it absolutely flew. Pretty much just like DV. I say this not to be argumentative Theirry, but just to say the newest machines have made a lot of headway in this area. It's very much in flux.

Very unlike the experience on my current dual 2.0ghz G5, which is barely sufficient and has gotten noticeably slower with the new FCP.

Just to close this whole thread out......
 

...several of our existing G-RAIDS were starting to show their age, and needed to be replaced. A 1 TB CalDigit S2VR Duo eSATA drive was just a little bit more expensive than a new G-RAID of comparable size, so we went that way. I've seen pretty reliable reports that the CalDigit drives will still run near 100 MB/s even when they are 80-90% full, so that should more than meet our needs.

The speed of the raid is never a problem with XDCAM HD. At 35MegaBit/s you only have a transfer rate of about 4.375MegaByte/s. You can achieve this with a single drive SATA with no problem at all. The datarate itself is just about 30% above simple DV. The bottleneck that will slow down the editing software is the MPEG GOP format. The more layers, the more CPU Power you need to do the edit. The drive will deliver the data very easily, but the computer has to crack the IBP frame structure (on every layer) to I-frames only again to be able to do transitions and titles and so on. As long as you just do hardcuts and don't plan to do uncompressed HD, a single drive in your PC or Mac or even a laptop is more than capable to deliver. It's the CPU that has do deliver not the harddrive.
I edit XDCAM HD on avid liquid without any problems from a single SATA.

Peter

Update on my above post.

You can find a very easy still in-depth view to the MPEG-2 technology here on this segment of digital Juice's TechKnow: http://www.digitaljuice.com/djtv/seg...how=all_videos


Peter