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io HD playback stutters
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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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[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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[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 -
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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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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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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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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Brian,
abandon this thread on Creative Cow. Contact Hector at AJA support with your information.bob Zelin
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