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Dropped frames during DigiBeta capture on G4 Power Mac

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Vladimir NovikovDropped frames during DigiBeta capture on G4 Power Mac
by on May 2, 2009 at 6:46:53 am

Hi all,

I got a chance to purchase some used video hardware, namely BMD DeckLink card, Sonnet Tempo 4+4 PCI SATA card and Sonnet Fusion 400P RAID enclosure. I've installed all this stuff into my Power Mac G4 2 x 1 GHz MDD with 2 Gb RAM to build a capture station for SD.

I boot from the internal ATA100 disk running Mac OS X 10.5.6 with all updates installed and the last drivers 7.1.2 from BMD.

I try to capture video from a Sony J30SDI player using the SDI cable and a RS-422 cable. I use BlackMagic Deck Control software, the clip goes to the RAID 0 strip on Sonnet Fusion which has been tested by Disk Speed Test and is more than adequate with 4 SATA drives in a RAID 0 strip.

However, it seems something goes wrong and after 20 minutes of capture using Uncompressed 10 Bit 4:2:2 PAL settings I get dropped frames and the capture stops.

What can go wrong? Any help will be very appreciated.


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Bob ZelinRe: Dropped frames during DigiBeta capture on G4 Power Mac
by on May 3, 2009 at 9:16:07 pm

there is a big difference between peak performance of your drives, and sustained performance. Your drives are not able to SUSTAIN capture at the correct speed. You see modern drive arrays on modern computers (MAC Pro's) with 600Mb/sec performance, and you say "who needs these speeds - this is faster than uncompressed HD". But when you get a spike in perforance of the drives while they are running, you get latency issues, and the drives stop for a moment - and this causes dropped frame errors. Slower drive arrays with better latency work better than fast drive arrays that have peaks in their perforamnce. Remember, you only need 30Mb/sec to do SD uncompressed video - it's not much, but you can't have any spikes in your performance.

Run the blackmagic or AJA system test. Do you see any of the lights "lighting up solid" when you run this test. It probably means that you have a questionable drive in your array.

Bob Zelin




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Vladimir NovikovRe: Dropped frames during DigiBeta capture on G4 Power Mac
by on May 3, 2009 at 10:04:57 pm

Bob, thank you for your replay. I've ran the tests from AJA, BMD and also HD Drive Speed Test I've got here http://www.unscale.com/DST.html, they all indicate it's OK for SD. I didn't notice any suspect lights.

I'm evaluating two things. First, Sonnet Fusion 400P itself has got some very good reviews when it was released, but the drives can be "a little bit tired" ;-) I've got four 250 Gb Maxtor drives inside. 1 Tb drives are cheap those days, some new single plate 500 Gb drives are even cheaper. What drives can you recommend to get a good four drives stripped RAID with correct sustained white speed?

Second, will I get any speed gain if I install SoftRAID? I've read some rather good and even enthusiastic reviews, but everyone mentions its superior monitoring capabilities. But what about speed gain?

Thanks a lot for your help.


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Bob ZelinRe: Dropped frames during DigiBeta capture on G4 Power Mac
by on May 3, 2009 at 10:39:28 pm

vlad,
a new MAC Pro with a single internal SATA drive can outperform what you currently own. I know exactly what his happening here. You have an older computer, can't afford a new one, and are trying to make the best of what you have. You are looking to add new modern hard drives to your system, and a better RAID program than Apple Disk Utility (like softraid).

Forget it. You have an old G4. It's over. You could accomplish what you want with an iMAC and a modern FW800 drive. But you have a Blackmagic card, so you need a MAC Pro (and a single internal SATA drive, like a Hitachi 1 TB drive for about $100.).

I dont' know how to assist you further. You can only push old equipment so far. Sorry I don't have better advice for you.

Bob Zelin




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Vladimir NovikovRe: Dropped frames during DigiBeta capture on G4 Power Mac
by on May 3, 2009 at 10:48:04 pm

Bob, fair enough. Thank you.

The problem is, not only I need a new Mac, I will also need a new capture device, because DeckLink is a PCI card, not PCIe. And a Mac Pro + AJA or BMD card or iMac + IoHD or MBP + MXO2 is out of question right now.

In all other cases I will end up with a DV quality from J30 using the built in FW port.

I was hoping to keep the current stuff as long as I don't need to deal with HD, but it seems I was wrong.

But it's not hopeless. I've reformatted the RAID drives and finally I've got my uncompressed 10 Bit 4:2:2 capture ;-))) Yes!!!

So, the question number 2 is to chose the codec for work, because you are completely right, if I even try to work with uncompressed stuff using this hardware, I'm completely out of my mind. Prores 422, Cineform, DNxND or IMX50?

Maybe I'll use the MDD just for capture, because it has the BMD card and the RAID enclosure with a card also compatible only with this hardware and buy an iMac for editing as soon as I can.


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Bob ZelinRe: Dropped frames during DigiBeta capture on G4 Power Mac
by on May 4, 2009 at 12:57:29 am

for limited bandwidth, nothing beats DVCProHD. About 14Mb/sec - you can easily do this without issue.

Bob Zelin




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Vladimir NovikovRe: Dropped frames during DigiBeta capture on G4 Power Mac
by on May 4, 2009 at 1:39:31 pm

Bob, did you mean DVCPro50? It's about SD, not HD. Any way, many thanks for your valuable help.


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