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Required data transfer rate for DV?

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Sangiovese
Required data transfer rate for DV?
on Aug 25, 2004 at 5:01:35 pm

Hi guys...

New to video editing (getting into it to help a friend). I've been looking around and found out that DV is about 3.5MB/sec (just under 13GB for an hour).

With that in mind, I have a couple questions.

Why are people saying that a striped raid setup is required for long projects? A decent quality IDE drive far exceeds that data transfer rate. (My Maxtor 120GB runs at 48.8 MB/sec average... as high as 68 on the outside of the platter, and down to about 32 in the very inside). So why RAID? Is there something I am missing?

I understand why you want a separate drive (on it's own channel) for your video storage, but I don't see why a striped raid would be necessary.

I've also heard that firewire is the preferred transfer method for external devices. It makes sense that Firewire is used, but why is USB 2.0 treated like a red-headed stepchild? The max transfer is higher (60MB/sec vs. 50MB/sec). Is there some other downside to USB that makes Firewire the preferred standard, or is it just that USB 1.0 wasn't fast enough so there is a lasting stigma?

How much bandwidth is required for audio? (I understand that there are different quality settings that would vary.. so I guess I'm looking for a range, or an estimate for above average sound quality.



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John Q
Re: Required data transfer rate for DV?
on Aug 26, 2004 at 3:06:07 am

You're right. Almost any internal drive available today can sustain the throughput required for multiple streams of DV.

I did use RAID on my video editing system, when the largest drives you could buy were 27 GB, barely sufficient to hold 2 hours of video. Today RAID only really makes sense for servers, where the RAID is a fault tolerant RAID 5 with hot swappable drives. I have a drive fail on my servers about every 18 months. Since RAID 5 has data redundancy, I can swap out the bad drive without losing a bit.

When the DV standard was written, the only practical choice was firewire.

DV audio is 48 KHz 16-bit stereo PCM. For DVD's, you can either use the PCM or recompress it to AC-3 to save more bits for your video. I typically encode my AC-3 at 192 kb/sec.


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