Poor quality output using new Hardware Acceleration and h.264

[UKMatt2000]

i7-8700K

GTX 1080Ti

Premiere Pro 12.1.1 (Build 10)

After discovering the new hardware acceleration feature I enabled the required BIOS option to allow the UHD 630 graphics to play alongside my 1080Ti, made sure the driver was up to date and found that it works perfectly with my i7-8700K. I then proceeded to render out a bunch of videos to h.264 with a 10mpbs target, enjoying the higher speed and lower CPU load. However when I checked one of the videos I noticed that the quality was extremely poor, despite only changing the hardware/software setting. I re-rendered it using software only and found that to be fine as previously, so it is the hardware accelerated rendering that is causing this. The files are the same size and are otherwise identical so this doesn't make much sense. Here are two screen grabs from the videos, I've made up a little clip in Forza Horizon 3 for demo purposes.

Software Only:

Hardware accelerated:

The difference is clear to see, very poor. As I've said these files are otherwise identical, at least as far as I can tell.

The only different output setting is the software/hardware option. It allows to set a high max bitrate but I can't see that making such a significant difference. For the sake of ensuring I bumped the hardware accelerated output up past 15mbps and it was still poor.

Can anyone shed any light on what's going on or what I'm doing wrong? Thanks

[Andy Urtu]

i7-8700K

GTX 570

Premiere Pro 12.1.1 (Build 10)

I just finished testing the new h.264 hardware acceleration also.  My source is Sony a7s II 1080p footage. I  output high quality 30 mbits per second, both hardware accelerated and non-hardware accelerated.

I had the same results as you.  The hardware accelerated h.264 output is MUCH lower quality, fuzzy, lack of detail and easily noticed even at high bit rates.

I tried a 2nd test. I added an adjustment layer to do some minor color correcting, This was much better, but still not quite as good as the software only.

I tried a 3rd test. During export I clicked the "Maximum Render Quality" check box. Again, much better, but still not quite as good as the software only.

[Vinay Dwivedi]

Hi Andy,

This feature is still under development and there are some limitations to i as of now.

One limitation I can mention looking at Matthew Tester's screenshot of Export settings that it is supported only for Level 5.1 and lower.

//Vinay

[Andy Urtu]

Here is some more info.  I used Profile 4.2.

What is causing the really bad quality is when I check the Key Frame box and set it to  60 (The source footage is 59.94)

    ORIGINAL                                                                      H.264 Hardware

Now, if un-check Key Frame box, the quality is very close to the original.

    ORIGINAL                                                            H.264 Hardware

[UKMatt2000]

I understand it's still in development, I'm struggling to find any detailed feature information though to give me an idea of what I should actually expect or how I should be using it. For example I did not know about the level 5.1 limitation. My original exports were using this but I raised it to ensure I hadn't missed anything.

I do not believe this is GPU related at all as I have tested it with the GPU acceleration turned off with no difference.

I have tried disabling key frames and had the same or similar quality improvement, how bizarre that it should make such a difference. Thank you Andy for testing this and posting your results.

Edit: Further testing shows that the quality is improved further by using level 4.0 with key frames turned off, however this limits the framerate to 30fps. Level 5.1 at 30fps is still awful.

[Jim_Simon]

These results actually do make sense.  Hardware encoding has long been inferior to software encoding.