Suddenly drop frame under un-compressed 8-bit SD


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Suddenly drop frame under un-compressed 8-bit SD
by Leo Leung on Jun 26, 2009 at 4:15:44 am

The system work fine about 2 year and found out the capture from BMD DeckLink HD PCIe drop frames and stop the progress under un-compressed PAL 8-bit SD coding to our Xserver (2.75T, RAID-5) or STARDOM (3T, RAID-5).

But, if the coding changed to DV PAL or PAL 8-bit JPEG it will be fine. I suspect the RAID througput problem, but after run the BM Disk Speed Test that the Xerver Disk Write rate to 167.5 to 189.4 MB/s. That's mean the RAID of write speed big enough for the SD uncompressed 8-bit.

I have no any idea of that.

Mac: 4 x 2.5Ghz PowerPC G5
Memory: 4G DDR2 SDRAM
OS X: 10.4.11
Storage: Xerver 2.75T RAID-5 and STARDOM 3T, RAID-5)

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Re: Suddenly drop frame under un-compressed 8-bit SD
by Bob Zelin on Jun 26, 2009 at 9:05:25 pm

1) how full is your drive array. You can't operate if your drives are full

2) what is your host controller card for your RAID ? We have found that many cards perform fine, but when you do a long show playout, the cards display latency issues, causing a dropped frame about 25 minutes into a show. You do your speed test, and everything seems fine.

BobZelin

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Re: Suddenly drop frame under un-compressed 8-bit SD
by Leo Leung on Jun 27, 2009 at 1:18:01 am

Bob, Thanks for your reply and help.

>>>1.) Xerver still have 80% space to be use.

>>>2.) Xverser use copper fiber channel for the data transfer. And, the r/w test performance fine.

If the DeckLInk and RAID array is fine, we may be figure out in between the DeckLink and RAID array have the problem.

We don't have another Mac to swap or test the storage, card and RAM.

Any further suggestion test to clarify the problem?

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Re: Suddenly drop frame under un-compressed 8-bit SD
by Bob Zelin on Jun 28, 2009 at 12:03:17 am

I am confused.

Are you using an Apple XServe as your FCP editing computer, or do you have a MAC on a fibre network, and using the XServe as a server, attached to your Stardom Fibre Channel array ?

If you are using an Apple XServe as your FCP editing computer, along with a Blackmagic card, this is pretty unusual. Open up RAID ADMIN, make sure all your Fibre drives are healthy. Go into the System Setup in RAID Admin, (your password is "private" to get into this), and make sure that CACHE FLUSHING is not checked. If it is checked, you will get dropped frames. At least, this is what happens with the Apple XServe RAID.

Bob Zelin

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Re: Suddenly drop frame under un-compressed 8-bit SD
by Leo Leung on Jun 29, 2009 at 5:26:30 am

Our main storage is the Apple XServe via two fiber channel to the Mac, and the STARDOM (firewire800) just for the backup purpose.

We run the BM Disk Speed test for the XServe as following result:

Disk Read Data Rate: 268.3 MB/s
Disk Write Data Rate: 187.7 MB/s

8 bit YUV 4:2:2 Frame Rate
PAL fps - Disk Read: 339 and Disk Write: 237

The above testing result the XServe throughput performance reach the requirement and suspect in-between the fiber channel and XServe have problem.

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Re: Suddenly drop frame under un-compressed 8-bit SD
by Leo Leung on Jun 29, 2009 at 6:33:45 am

I found out the XServe of the "CACHE FLUSHING" checked and take out from the check box then back to normal capture status and no any drop frames occur.

But, I still have no idea why this setting to be change.

Thank Bob so much for your help!

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