Disk Speed Test – IS THIS OK?

[Jim Leonard]

My DeckLink SP is in a plain 2.6GHz desktop with a single RAID-0 array (two disks striped together) and my numbers are very similar to yours and it works just fine. In fact, I’m using it to finish up a PAL and NTSC project right now.

[Jimmy Brunger]

Plugged it all in and had a fiddle…Deck Control works a treat, plus I can grab stills and PLAY video, but not capture video or lay off video. Drops frame too much..

I think my drives are too slow and are not striped. Do I really need 10,000RPM SATA drives? Would 7200’s do the trick? I was going to get more storage anyway but 10k ones cost a helluva lot more!

Still capture and deck control is good enough for now, until I get more drives.

Any tips for cheapish drives appreciated.

*AE 5.5 Pro – *PS CS1 – *Combustion 3
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Win XP Pro SP2 / Intel P4 3GHz / 2GB RAM / GeForce FX5200 / BMD DeckLink Pro / Sony BVM-20G1E / DVS SDI Clipstation

[Jim Leonard]

I striped two 7200RPM drives together and it works for me. But my numbers are similar to yours — it’s possible you have a motherboard that doesn’t handle bus traffic very well or something.

[Luke Maslen]

Hi,

In theory your internal disk is fast enough for SD capture and playback. You’re working in PAL so you need at least 25fps capture and playback. The real test comes when your hard disk fills up as it will slow down. As you are only working with a single drive, there will be signicant fluctuations of disk speed and that could be your problem. I am puzzled that you found you could playback video without problems but you could not capture without dropping frames. Playback of uncompressed video is more demanding than capture so your observations are the opposite of what I would expect. Were you playing back uncompressed video or were you playing compressed video?

One test you could try is to have Deck Control capture using a PAL JPEG easy setup. This will capture your video in a compressed format which will be much easier for a single disk to do. If you still encounter dropped frames, then some other issue is the cause of your problem and we would need to look in to that. However if the dropped frames go away as a result of capturing with the JPEG compressed codec, then this would suggest a disk-related issue which could probably be overcome by striping 2 or more disks together. 2 x 7200 rpm SATA disks should be fine.

Regards,

Luke Maslen
Blackmagic Design

[Jimmy Brunger]

Hi Luke,

Thanks for the advice – I tried capturing from digibeta in easy JPEG setup and worked fine! I pretty much knew I was going to have a problem with uncompressed until I can stripe a couple of drives but I just wanted to try it. My system has pretty much defied the min spec requirements already and I wanted to see how much I could get out of it! (865p chipset and 32bit PCI slot – Asus P4P800 Deluxe board)

So 7,200rpm drives should be solid for uncompressed SD then? I just want to be sure before shelling out for a TB of storage! How come the min spec requirements state 10,000rpm then?

Also, sorry to be a question machine right now..but can you explain the ‘safety margin’ bit on page 3 of the DL manual? Not quite sure quite how to calculate what I need to..

For your reference – when I said playback worked I meant that I could mount a QT mov into Deck Control and play it back without any jumping or stuttering. It was a BMD 8bit Quicktime, so I guess not STRICTLY uncompressed. I can also playback the output from the digibeta deck and get it to monitor fine on my broadcast mon. When the QT mov plays back I can view it on my broadcast mon, but the left viewer in Deck Control remains frozen until I pause it, I presume that’s normal.

I couldn’t however get the 8bit BMD to lay off to the deck – it dropped frames. However when laying off the JPEG footage back to tape, it let me do it but the resulting footage on the tape was all out of vertical sync and had gone a nasty posterized green and pink! Any clue what that might be? My first thought was genlock timing but I have no idea where to start with that.

[Rolls eyes] I’m not an engineer, just a lowly graphic artist. but I’m trying to learn!

*AE 5.5 Pro – *PS CS1 – *Combustion 3
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Win XP Pro SP2 / Intel P4 3GHz / 2GB RAM / GeForce FX5200 / BMD DeckLink Pro / Sony BVM-20G1E / DVS SDI Clipstation

[Jimmy Brunger]

Switching everything off and on to try get things working I have managed to successfully dump to tape (JPEG and BMD 8bit – odd!) It turns out that have blackburst output to SDI outputs switched *ON* was causing all the problems. I assumed it should be on to sync up the deck, but actually switching if off made everything work. Bizarre.

Full JPEG capture & dump to tape is working fine now, but 8bit BMD is still a little iffy to capture (after new drives in RAID 0 I’m hoping it will be OK) However printing 8bit BMD to tape, as I said works..which as you said Luke, SHOULD be more drives intensive than capture, but seems not.

Thoughts?

*AE 5.5 Pro – *PS CS1 – *Combustion 3
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Win XP Pro SP2 / Intel P4 3GHz / 2GB RAM / GeForce FX5200 / BMD DeckLink Pro / Sony BVM-20G1E / DVS SDI Clipstation

[Jim Leonard]

“So 7,200rpm drives should be solid for uncompressed SD then?”

Yes. I do it all the time with 8-bit; not sure if that’s enough for 10-bit or higher though.

“How come the min spec requirements state 10,000rpm then?”

Because you DO need that for HD 🙂

[Jimmy Brunger]

Good stuff. I’ll only be using 8bit SD (& poss 10bit SD) but we’ll be upgrading everything for HD at some point so I don’t need to worry about that with this machine.

I only asked because the min specs for SD stated 10,000 RPM drives, HD specified 2GB Fibre Channel or SCSI drives.

*AE 5.5 Pro – *PS CS1 – *Combustion 3
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Win XP Pro SP2 / Intel P4 3GHz / 2GB RAM / GeForce FX5200 / BMD DeckLink Pro / Sony BVM-20G1E / DVS SDI Clipstation

[Luke Maslen]

Hi Jim,

You have been pushing the limits of your hardware but I’m glad to see you’ve got this far. Can you give me a URL for the information that states that 10,000 rpm disks are needed for SD as I cannot find it. It might be from an old support note that I’ve overlooked. 10,000 rpm disks used to be very important but 7200 rpm is usually fine now.

The safety margin is a rubbery figure and trial and error is involved. SATA disks are inexpensive compared to previous disk technologies. However they also tend to slow down more as they fill up with files. In the past, I would have suggested you use at least four disks for uncompressed SD but now two will do. Three would be even better but two will suffice.

[jimmybee500] “It was a BMD 8bit Quicktime, so I guess not STRICTLY uncompressed.”

Actually it is strictly uncompressed. However if you are referring to the color bars movie, then it is only a frame or so and there would be no problems playing it back as it will just load in to RAM and playback without issues. It’s when you’ve got a longer movie that you would see problems and that seems to match your observations.

Deck Control is an aging utility and hopefully we’ll update its interface soon to show live updates in it during movie playback. Premiere Pro would give you far better feedback during capture and playback but we should also get around to updating the interace on Deck Control.

The green and pink output is strange with the QuickTime PhotoJPEG codec. Do you see the same when outputting the same movie from After Effects or Combustion via RAM preview?

Regards,

Luke Maslen
Blackmagic Design

[Jimmy Brunger]

Hi Luke,

Thanks for your feedback. I sorted out the pink/green picture on lay-off…Turns out the ‘Black Video Output to Deck in Capture’ was actually sending the digi deck out of sync! I tried analogue/digital and disabled – disabled seemed to make it work. This was with a deck directly hooked up to the card (SDI in/out) and no genlock (genlock didn’t make any difference) however I may have to fiddle with the settings a bit more when hooked up through the machine room patch bay, but we’ll see what happens.

As for the SATA drives, I was thinking of getting 2 or 3 of these, depending on how many drives the RAID controller on my motherboard can handle:

https://www.misco.co.uk/productinformation/~Q74482~WW~/

Do they look suitable do you think? I’d rarely capture more than a couple of minutes footage at a time, as we work mainly on TVCs..so demand on the drives should be too much?

The test QT movie I was playing back was a 1 min clip I had on the system already that I rendered out of AE from an AVI. Seemed to playback fine, like I said.

I’ve just ordered Adobe Production Studio, so will have Premiere for capture/playback by end of the week hopefully. A Deck Control update would be good though, as booting Premiere everytime I want to playout a few GFX will take up valuable time and booting Deck Control is almost instantanious.

Any idea what the chroma/luma shifts are all about when using the BMD 8bit codec? I may have mentioned it in the other thread about GRAB FRAME vs PS IMPORT, but it is a bit of an issue. Is it normal?

*AE 5.5 Pro – *PS CS1 – *Combustion 3
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Win XP Pro SP2 / Intel P4 3GHz / 2GB RAM / GeForce FX5200 / BMD DeckLink Pro / Sony BVM-20G1E / DVS SDI Clipstation