CUDA = chunky video?

[DarioD]

Hi, all.
Whenever I encode with the CUDA encoder, the video comes out chunky, no matter what my H.264 settings are. Am I doing something wrong? It's as if CUDA is getting its settings from somewhere else.

(my video card is the nVidia GTX 260)
Thanks!

[DarioD]

Anyone?

[rosenhauer]

It seems that when using CUDA it ignores the "Video" settings and just does some low quality default setting.

So until this is fixed CUDA is worthless for me.

[Jamesbond007]

I just installed Mediacoder 2011 R1 5100 on a system using Intel Core 2 Quad Q9550 and a GTS450 video card and tested the conversion of a 720p MKV file to MP4 using CUDA and x264 encoders (CPU). It is quite obvious to me that even though using CUDA used just one quarter of time to convert the video file versus using CPU (9 minutes vs 36 minutes), the quality of the video converted using CUDA was noticeably worse than that converted using CPU.

Although this is to be expected given what I have read elsewhere about tests done on CUDA vs CPU encoding, it is still disappointing when I saw the result in person.

I will test again later after my planned upgrade to Sandy Bridge later this year as Mediacoder 2011 apparently already supported using Quick Sync. I shall see if Quick Sync will give faster encoding speeds without suffering from the quality problems with CUDA encoding now.

[AnonCrow]

To really change the quality of CUDA encodes, I find that one needs to go to CUDA advanced options and enter the desired QP levels for I/P/B frames there -
something like 16/18/22 for high bitrates , upto maybe 25/28/31 for low bitrates (barely acceptable quality)

[kwreid]

This is a regression from the previous build.

I was using the iPod 64bit version build 5016 and updated to 5100 and I noticed the same effect when using CUDA. Using my previous version I had no such quality issues.

[DarioD]

[thread resurrection] Is a fix for this on the way? I'd really like to encode via CUDA.

To really change the quality of CUDA encodes, I find that one needs to go to CUDA advanced options and enter the desired QP levels for I/P/B frames there -
something like 16/18/22 for high bitrates , upto maybe 25/28/31 for low bitrates (barely acceptable quality)

Thanks, but everything comes out the same. I'm clicking "Save" after changing the numbers, and trying random other ones as well. Am I missing something? Encoding Preset = Custom, and Bitstream Profile = Baseline.

[AnonCrow]

[thread resurrection] Is a fix for this on the way? :) I'd really like to encode via CUDA.
Encoding Preset = Custom, and Bitstream Profile = Baseline.

At least use Main or High profile instead of Baseline.
Dynamic GOP, Cabac and most importantly deblocking enabled ?
IDR period ? 15 is really the minimum, 10-20 times your FPS could be better, unless you need a short keyint for compatibility reasons (blu-ray).
How many B-frames (2-5 would be reasonable, 8 for animated video, anything over 10 is an overkill) ?
Try some extreme QP values; like 1 for all three.
What's the mediainfo detailed info , bitrate, fps, resolution like on an encoded video ?

[DarioD]

Woot, it all started working as soon as I increased the IDR period. (MediaCoder's regular Video Bitrate slider also affects quality again.) Thanks a lot!

Update: Actually, the IDR setting 200,000 seems to give the least "trail" behind moving objects, at least in 720p, 60fps videos encoded at super low-quality. (In high-quality renders, it's almost impossible to tell the difference between any settings.)
Update 2: ...and it makes occasional blotches on faces. Well, back down to 300, which seems like the best balance for these particular clips, right now.

[AnonCrow]

Update: Actually, the IDR setting 200,000 seems to give the least "trail" behind moving objects, at least in 720p, 60fps videos encoded at super low-quality.

A 200k keyint is crazy, with 60 fps material that would mean only one keyframe about every 55 and a half minutes.