quick sync vs gpu vs cpu

ushere wrote on 4/29/2013, 9:45 PM

ok, new laptop has quick sync.

it's very, very fast rendering certain formats (and is apparently coming to handbrake).

however, i'm reading that it's quality isn't as good as gpu, which i've also read isn't as good as cpu. regarding the latter i haven't seen / experienced any problems with either gpu or cpu renders - they both look equally good.

what's the (abbreviated) story with quick sync?

as ever, thanks in advance ;-)

Comments

NormanPCN wrote on 4/29/2013, 9:53 PM

Quicksync is a hardware GPU encoder.
Some other GPU encoders are CUDA or OpenCL based.

GPU encoders to date have not had the same visual quality level as more mature CPU encoders. This really only shows up when you push the bitrate down low. Most everything does well at higher bitrates.

More info than you want, but here is a link for the curious.
compression.ru/video/codec_comparison/h264_2012/

ushere wrote on 4/29/2013, 10:23 PM

thanks norman (?)

i came across that comparison during my 'research'. very comprehensive.

so, from what you, and many others have written, the main 'problem' with quick sync (and in some cases gpu) is encoding at low bit rate. exactly how low are we talking? i mean, if i want to put something up on youtube / vimeo at their recommended bit rate would i see a 'noticeable' difference. alternatively, when i knock out high quality mp4's for clients would i see a difference?

i might add i'm not a pixel peeker and i doubt any of my audience would see the difference between 720 and 1080, etc.,

NormanPCN wrote on 4/30/2013, 1:06 AM

Yes it's Norman,

I am not one to tell others what is good/acceptable. You just have to try it and look for yourself, as I have. It is a pain but you are your best judge.

Having said that, I upload to my Smugmug account and I have seen SonyAVC 3Mbps 950x540 files not be as good as 1.8Mbps x264 files. Both High profile. I got a little better Smug re-encode with the x264 upload. I took to uploading a 3Mbps x264 encode. Smugmug encodes those files to 1.8Mbps. I use DNxHD as an intermediate and use Handbrake to encode the H.264 m4v file I upload.

I did play with the Main Concept OpenCL encoder and it is really close to my camera quality given the same bitrate. 20Mbps 1080p30.

The Main Concept AVC CPU encoder is probably the best quality out of the box in Vegas, but OMG is it SLOW! Of course DNxHD is stinking slow too.

Loved using the OpenCL encoder. It speed was blazing. Good for quick test encodes to watch your vid. Unfortunately it does not like my new video card.

For me, I would use the fastest GPU encoder that works for me to general test encodes and good bitrate. Then if you want max quality in H.264, hands down no question, regardless of bitrate, go with x264 via some intermediate. Otherwise Main Concept AVC 2-pass CPU for max Q straight from Vegas.

john_dennis wrote on 4/30/2013, 7:34 PM

Some of my original Quick Sync results in this thread.

ushere wrote on 4/30/2013, 11:49 PM

thanks john, appreciated.