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Brian Cutts
io HD playback stutters
on Aug 11, 2009 at 4:40:26 pm

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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Jeremy Garchow
Re: io HD playback stutters
on Aug 11, 2009 at 4:58:18 pm

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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Brian Cutts
Re: io HD playback stutters
on Aug 11, 2009 at 7:11:34 pm

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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Jeremy Garchow
Re: io HD playback stutters
on Aug 11, 2009 at 7:23:39 pm

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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Brian Cutts
Re: io HD playback stutters
on Aug 11, 2009 at 8:11:47 pm

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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Brian Cutts
Re: io HD playback stutters
on Aug 12, 2009 at 2:54:52 pm

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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Jeremy Garchow
Re: io HD playback stutters
on Aug 12, 2009 at 3:23:26 pm

[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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Brian Cutts
Re: io HD playback stutters
on Aug 12, 2009 at 3:30:40 pm

[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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Jeremy Garchow
Re: io HD playback stutters
on Aug 12, 2009 at 3:41:50 pm

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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gary adcock
Re: io HD playback stutters
on Aug 13, 2009 at 11:14:22 am

[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





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Jeremy Garchow
Re: io HD playback stutters
on Aug 13, 2009 at 1:13:24 pm

Ah, in that case maybe the airport/network as well?


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gary adcock
Re: io HD playback stutters
on Aug 13, 2009 at 4:47:53 pm

[Jeremy Garchow] "Ah, in that case maybe the airport/network as well?"

started seeing these issues on the highend capture- like to 2K DPX and found that on older or marginal machines YES often something as simple as the airport constantly looking searching for a network to connect to could affect capture.

there are so many things that by themselves only consume 1-2% of the CPU but you add to the airport, polling for DHCP, NTP (timeservers) and all of a sudden your using 12-15% of the CPU in overhead processing in the background.

While I am not saying that is the case here, ( I think it was how the files were created) or that he was using a masked image (alpha) in a codec that is not currently supported on the IoHD.

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflow for the Digitally Inclined
Chicago, IL





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Brian Cutts
Re: io HD playback stutters
on Aug 13, 2009 at 1:50:41 pm

OK, looks like we're starting to win... thanks for your help so far.

Mixing down the audio seems to have fixed the problem. We had a three playouts yesterday and they all worked if we mixed down the audio. Incidentally the edits are simple single video layer (with some dissolves) and two tracks of audio.

I can certainly confirm that there are no frame rate mismatches or material stored on the internal drive.

So I guess I'm correct in thinking that the issue is down to system performance - maybe drive throughput - and the system is actually dropping frames. Is it possible for frames to be dropped but not reported?

If it's down to performance then I guess we're right on the edge and if we create sequences with more complexity we could have the problem re-occur. Is it fair to expect our system to be able to work in ProRes HD?

Brian



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Jeremy Garchow
Re: io HD playback stutters
on Aug 13, 2009 at 2:26:03 pm

[Brian Cutts] "Incidentally the edits are simple single video layer (with some dissolves) and two tracks of audio. "

And where's the audio coming from? Embedded in the QT?

[Brian Cutts] "So I guess I'm correct in thinking that the issue is down to system performance - maybe drive throughput - and the system is actually dropping frames. Is it possible for frames to be dropped but not reported? "

There's a preference for this in FCP User Prefs. Report dropped frames on playback and Abort ETT/PTV on dropped frames.

Remind of your drive setup again? Also, computer, RAM, and Express34 card?

[Brian Cutts] "If it's down to performance then I guess we're right on the edge and if we create sequences with more complexity we could have the problem re-occur. "

Maybe, but a full rt render of your timeline, and a mix-down of the audio is a good way to 'simplify' the playback of your timeline without the export and subsequent reimport. Keep in mind that 'mix-down' is not what you usually think it is, a la Avid. The render mix-down in FCP simply takes all the audio files and combines them in to one temporary render. It does not take 8 tracks and make it two. If you have 8 stems outputting, the mix-down will keep those 8 stems, but will render one 8 channel audio file for easier and smoother playback. Some people get scared of the work mix-down as it means something totally different in Avid.

[Brian Cutts] "s it fair to expect our system to be able to work in ProRes HD? "

I would say you should be able to do it. I have a 2.33 Ghz MBP (the lowest recommended system for the ioHD) and it works.

Jeremy


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Brian Cutts
Re: io HD playback stutters
on Aug 14, 2009 at 7:36:50 pm

Hi Guys,

Well the problem has started again... arggg!

I've checked the FCP preferences and report dropped frames is turned on for ETT & PTV. I've disabled the Airport & Bluetooth modules as well as anything else I can think of. There are no other apps running and nothing is set to run under user login.

Fully rendering the sequence (both video and audio) does not fix the problem but the export/import does seem to as far as I can tell. The export also plays fine under AJATV.

I've tried swapping the MacBook Pro out for another unit (of higher spec) and the problem remained when using that unit so it looks to be related to the 3rd party hardware.

As a reminder, we are using the AJA IO box with the latest software drivers & firmware connected to the onboard FireWire 800 port, a G-RAID 2 2TB drive connected via a FireWire 800 Express34 card. This card is a Dynex DX-ECFW 800 card. I'm wondering if maybe this is the root cause of the problem. I've been reading up on the G-RAID site and they only 'qualify' their own FW800 Express34 card.

I also see that the G-RAID 2 uses the Oxford 924 FireWire chipset. I know from my Avid experience with Adrenaline that connecting FireWire devices which use different chipsets can result in some 'interesting' issues so is replacing the Express34 card a reasonable course to take? G-Technology don't seem to supply their own one now as far as I can see and they don't seem to recommend any by 3rd party manufacturers... do you guys have any recommendation?

Brian



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Jeremy Garchow
Re: io HD playback stutters
on Aug 14, 2009 at 7:52:35 pm

Sonnet is a good one.

http://sonnettech.com/product/fw800expresscard34.html

Jeremy


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Bob Zelin
Re: io HD playback stutters
on Aug 14, 2009 at 10:39:13 pm

Brian,
now, I want you to listen to me. You need to do this for me, because it is very important. I know you are busy, but do this anyway.

Playback your "stuttering" sequence, and output it to a VTR. If you don't have one there, find one, and output it to a VTR - one that you can go back and check "frame by frame" - with a jog wheel on the VTR.

When you say "stutter", you can't really tell what is happening, and you are not getting a "drop frame" error. When you playback your sequence, and you see that "stutter" once or twice intermittently, I want you to jog up to that "stutter", and look at it FRAME BY FRAME.

I want to you to tell me if it's a "stutter", or if you are seeing the frame repeating itself, or even worse, it goes back a frame and continues, giving a "Max Headroom" appearance to the video at that moment. If you are seeing exactly what I am describing to you, then people bigger than you or I (or anyone on this list) need to address this issue, and I will make sure that this happens.

Please do this test ASAP, and let me know what you find.

Bob Zelin




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Brian Cutts
Re: io HD playback stutters
on Aug 14, 2009 at 11:56:50 pm

Bob,

Excellent idea. That's exactly what I've done and it does actually go BACK a frame!! In fact on one instance it went back a frame and then missed out a frame before going on to the next frame.

So I guess that blows the whole system bandwidth theory right out of the window?

Brian



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Brian Cutts
Re: io HD playback stutters
on Aug 15, 2009 at 2:45:26 am

I've also captured the footage exhibiting the stutter back to FCP, clipped the 'offending' sections and created an export - all using the same codec as the original. The file is around 17 seconds long and about 250MB. I can upload it to my personal .mac site if it would help you in seeing the problem first hand.

Brian



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Bob Zelin
Re: io HD playback stutters
on Aug 15, 2009 at 3:26:31 pm

Brian,
abandon this thread on Creative Cow. Contact Hector at AJA support with your information.

bob Zelin




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Bob Zelin
Re: io HD playback stutters
on Aug 15, 2009 at 3:27:31 pm

Brian,
please send me your direct email to
maxavid@cfl.rr.com

Bob Zelin




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Jeff Kirby
Re: io HD playback stutters
on Aug 16, 2009 at 11:22:01 pm

Mine does the same thing, but it repeats a frame, then skips a frame, then continues at a normal rate. Also, I find my stutter problem occurs when the action on-screen is fast-moving (I work with hockey footage primarily, and the times when a puck it shot, or someone is hit, and the camera pans, the stutter tends to happen). I am going to call AJA this week and see if I can have someone look at it, as I need to be using it full-time again in October.


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Bruce Rawlings
Re: io HD playback stutters
on Aug 29, 2009 at 8:37:15 pm

I have the same problem when using my MBP. Material plays perfectly when project and drive connected to a MacPro machine with a BlackLink card.



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Joseph Harkins
Re: io HD playback stutters
on Jun 15, 2011 at 8:50:08 pm

I know this is an incredibly old thread, but I am having that same problem Brian described and am wondering if he ever got a fix.


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