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io HD playback stutters
Hi,
I’m having a problem with HD playback of material using a MacBook Pro where we get the occasional stutter which looks almost like a dropped frame.
The setup uses the AJA io connected to the onboard Firewire port and a G-RAID external drive connected to a Dynex EC-FW Firewire 800 plugged into the card slot. The MacBook Pro is a 2.5GHz machine with 4GB RAM and is running FCP 6.0.5.
I’m pretty sure that it’s not dropping frames during output since it does not stop playback if I turn on ‘report dropped frames’.
We are working in ProRes 422 – in non HQ mode and the AJA drive test gives around 60 MB/sec write and 70 MB/sec read so the drive seems fast enough. We’ve also tried swapping the AJA io and the drive over to see if it makes any difference but it doesn’t. However, if export the sequence as a self contained QuickTime file and bring that back into FCP it seems OK.
Any ideas what else we can try? It’s a pain because we often have to play out live so don’t have time to render down to a single self contained QuickTime file.
TIA, Brian
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23 Replies
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Format and frame rate of material, and where did it originate from?
A guess is that you rendered something out of a graphics program @ 23.98 and not 23.976. You are putting this in a 23.98 (which is really 23.976) timeline and it stutters. Then you export it out and reimport and now the file is properly 23.976 (even though FCP says 23.98 for shorthand). Then it works.
Is it something like that?
Jeremy
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Thanks for the response to my question.
Format of the material is all encoded using Apple ProRes 422 1080i/60. Actually 29.97. Media is delivered from an EVS also running Apple ProRes via XTAccess.
There are no graphics imported, no progressive material and no strange frame rates. The stutter happens around once or twice a minute.
I’ve also checked to make sure it’s not a reference problem – ref is tristate – by removing it and also using a SD ref.
I’ve also got a MacPro on site with a BlackMagic card, attaching the media drive to that, opening the project and playing the sequence is fine on that system so I’m pretty sure it’s not an issue with the media.
Brian
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Cool, now that we got all that goodness out of the way, have you tired uninstalling and reinstalling the ioHd Drivers and made sure the firmware was up to date?
Jeremy
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Haven’t tried an uninstall/reinstall. We’re is busy cutting a news package at the moment but should be able to try that in a couple of hours. With luck we will not be tight for time on this package and will have time to export the sequence.
I’ll get onto the AJA site and make sure we have the latest software. I’ll get back to you with the results.
Brian
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Hi Jeremy,
Went through the complete uninstall / reinstall / update firmware process yesterday evening. Initially it looked like it may have fixed the issue but on closer inspection it seems not.
The best way to describe the issue is that it seems that the image hops sideways.
Any more ideas… perhaps we have a faulty io box?
Brian
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[Brian Cutts] “The best way to describe the issue is that it seems that the image hops sideways. “
Sounds almost like a reference issue. Is it in the acutal file or just on output? Open the captured file in QT to check.
[Brian Cutts] “perhaps we have a faulty io box?”
Maybe? Although I don’t get the feeling that it is.
Jeremy
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[Jeremy Garchow] “Sounds almost like a reference issue. Is it in the acutal file or just on output? Open the captured file in QT to check.”
I’ve tried it without the reference connected and we get the same issue. If we export the file and bring it back into FCP as a single clip then it’s fine. Also when playing the problem sequence in FCP the issue does not seem to be present in the desktop window although it’s pretty subtle so it would be difficult to see anyway.
If it’s any help, we get the same issue when working Stateside at 1080i/60 and also in Europe at 1080i/50.
Also the hop is not always in the same place so I don’t think it’s a problem with the actual file. We can play the sequence and it hops at T/C a… play it again and it no longer hops there but hops at point b.
Brian
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So, this is only happening on the output of the AJA then, but what is odd that if you export a movie then reimport that it works. What that says to me is that either there’s a mismatch of frame rates somewhere (like 30 vs 29.97) or your drives are having a hard time keeping up, but aren’t reporting the droppped frames. If you select all in the timeline and then hit command-option-r to mix down the audio, does the problem go away? How many tracks of audio? Is absolutely all of your media on your external drives? no audio, or still frames or anything is on the boot drive, correct?
Jeremy
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[Jeremy Garchow] “So, this is only happening on the output of the AJA then, but what is odd that if you export a movie then reimport that it works. What that says to me is that either there’s a mismatch “
good catch, but it is not a mismatch of frame rates, but with the codec implementation playback. since the glitch is not in the same place every time. I think it has to do with some other process on your computer that for short periods it is taking enough power from your CPU to make the video skip.
Try playing back the file in AJA TV and see, since it requires less overhead to operate for playback, you should not see stuttering, if you do then you need to systematically check to see if it is the Storage, the FW connection or the IoHD.
gary adcock
Studio37
HD & Film Consultation
Post and Production Workflow for the Digitally Inclined
Chicago, IL -
Ah, in that case maybe the airport/network as well?
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