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4770k OC for Video Encoding... no performance gains

post #1 of 4
Thread Starter 
So i recently created a gaming rig that I also use for 3D modelling, Video encoding, etc. This was my first attempt at overclocking and I did it mostly to speed up my bluray rip/encode process. I needed to keep my overclock at safe temps/voltages since transcoding a single bluray takes over 24 hours from start to finish using my setup.

I have the following setup:
4770k i7
Corsair H50 Heatsink
16 GB DDR3 running at 1600 MHz
ASUS Z87-G45 Gaming Mobo
1TB WD Black HD
EVGA Geforce GTX 760

My overclock is set to 4.4 GHz at 1.35V, sadly when I tried to push it further at the same voltage it would BSOD. I didn't want to push it above 1.35V since it would be running for 24+ hours at 100% capacity and going above 1.4V seems to be considered "Dangerous" the 4770k. Regardless, I would probably start breaking into undesired temps if I went any higher (I know I could get better cooling, but there isn't much point if OC does nothing for my encodes). During the entire process I have an average temp of 70c and an occasional peak at just under 80c which is right where I wanted it.

I use ffmpeg with the following parameters:
ffmpeg -i input -strict experimental -map 0:0 -map 0:1 -map 0:1 -c:v libx264 -preset placebo -crf 17 -c:a:0 aac -b:a:0 192k -c:a:1 ac3 -b:a:1 192k output

Now I know these aren't the best encoders on ffmpeg, but to get the best I would need to compile from source to get the best since they are part of the nonfree encoder set. I just wanted to compare two encodes with roughly what I wanted.

At stock settings (well... after updating my ram speeds from 1333), my transcode averaged about 1.6-1.7 frames per second encode at 3.7-3.9 GHz after turboboost kicked in.
At OC settngs, my transcode averaged about 1.6-1.7 frames per second encode at 4.4 GHZ (turbo disabled, of course).

What is going on here? Why do I seem to get absolutely NO performance gain despite a 10-20% increase in CPU speed. Ideally I should see a 10-20% increase in my encode speed (somewhere around 1.9 - 2.0 fps).

Disclaimer: This was NOT measuring the entire encode. The OC encode ran for 6 hours before I killed it, the stock encode ran for 1.5 hours before I killed it. This was a preliminary test. I am currently doing a full encode test, but it will take ~48 hours to finish.
post #2 of 4
Thread Starter 
Anybody? There is only so many practical reasons for overclocking. Has anyone done it to speed up video encoding? Have you experienced negligible change in throughput due to OC or have you noticed significant increases/decreases? I just want to know if I am missing something here. Perhaps overclocking does not affect video encoding rates.
post #3 of 4
try encoding a smaller file and see if it takes less time to encode.
my 955be and fx8120 have performed better when overclocked with handbrake and convertxtodvd, not sure which program you're using for those ffmpeg settings.
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post #4 of 4
Try this benchmark: http://downloads.guru3d.com/x264-FHD-Benchmark-v1.0.1-64bit-download-2825.html If it doesn't show a marked difference from stock to overclock something else is wrong.

Fire up handbrake or ripbot (ripbot has 10bit support as it's just a frontend for 264) and do a few sample clips to change your settings - a 2pass encode will generally give you better results @ a lower filesize without having to stick it in placebo mode, placebo is a massive increase in encode time for an almost imperceptible increase in quality.
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