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Real-time playback of 4k DNxHD HR files

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Chris Wade
Real-time playback of 4k DNxHD HR files
on Jun 26, 2016 at 9:21:18 pm

Greetings again, CreativeCow experts. I have a question on my Avid workflow that is baffling me.

I've been working with 4k files from the Red Scarlet camera, and I've never had an issue. Trailers, music videos, promo videos, instructional videos...I always work with 4k footage, no problems.

Now I'm editing together a short film. It's the largest project I've worked on so far. I cleared all of my old projects and started fresh, and everything worked as per usual, but this time, I'm having severe stuttering. Granted, I'm working at a demanding data rate, but I've never had any issues with this previously.

My basic workflow is this:

1. Link to 4k .R3D files in Avid.
2. Subclip .R3D files to sync'd audio files.
3. Transcode those files to DNxHR HQX full res footage. (I've used the codec since it was released with no issues...wishing I had transcoded to DNxHR SQ now, but this is a LOT of footage...)
4. Seperate resulting footage into bins by scenes.
5. Put original AMA files and subclips in bins marked "Delete"
6. Create seperate sequences for each scene
7. Edit

My computer isn't the best thing in the world, but it's no slouch:

Intel i7-4790k overclocked to 4.7GHz (watercooled)
nVidia GTX-980 Ti overclocked to 1.4GHz Clock and 4.1 GHz Memory (watercooler)
9tb RAID 0 (Striped) media drive (3.5TB free; this is where all of the media files are located)
512GB RAID 0 (Striped) SSD OS drive (250GB free; this is where all of the operating system and Avid program files are located)
Dual Samsung 28" 4k (UHD) monitors (could always bump these down to 1920x1080 to ease the video card's workload, but again, I've always worked like this with no issue, and I'm hesitant to do that...I think I'd prefer to bump quality down to SQ first).

Here are the steps I've taken so far to eliminate the stutter:

1. Quality set to "Best Performance" mode (which I've never had to do before. I typically work in "Draft Quality" or "Full Quality".)
2. Working in proxy mode (which I've never had to do before, and the quality loss is extremely irritating). At 1:4, the stutter is still there and unbearable. At 1:16 it's almost gone, but I can't see my actor's mouths due to quality degradation.
3. Minimized timeline to just a single audio and single video track.
4. Eliminated any effects unless absolutely necessary. I rendered the one unavoidable effect to the timeline.

Not sure what else to do, other than re-transcoding the entire project back to DNxHR SQ, which seems like it will take forever. Any ideas?


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Robert Dian
Re: Real-time playback of 4k DNxHD HR files
on Jun 26, 2016 at 10:12:44 pm

cpu usage ?
disk usage ?
disk speed / benchmark ?
what raid ? Intel RST ? what drivers ?

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Chris Wade
Re: Real-time playback of 4k DNxHD HR files
on Jun 26, 2016 at 11:19:36 pm

Just played a 3 minute sequence from beginning to end. By the end, the audio was almost 7 seconds ahead of the video due to stutter.

This is despite having changed the format to a 2K preset, turned proxy on to 1/16 (512x272 resolution), and adjusted the display resolution of both monitors down to 2K.

CPU utilization during the entire clip was 100%. Temp peaked at 100 degrees C. Not good, especially on a system with an $800 custom water cooling setup on it.

I removed all overclocking on the CPU and saw an improvement in performance (makes me think the guy who did my OC work didn't know what he was doing). Audio was only 1.5 seconds ahead of video by the end, but CPU utilization and temps still hovered at 100 each.

Even with nothing running and CPU at 1% utilization, my CPU temps are hovering at around 74 degrees C. Something's not right.

I never would've started digging into that without your questions, so I appreciate it. Apparently I have a PC issue. May need to re-seat the CPU. I'm going to do some hardware troubleshooting.

Thanks again! At least it's not my Avid! :)

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Robert Dian
Re: Real-time playback of 4k DNxHD HR files
on Jun 27, 2016 at 7:45:32 am

74 in idle is problem, in load CPU start throttling = problem

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