How do I test my CPU/iGPU for smooth video playback?

geoto · March 18, 2016

Hello guys!

CPU - i7 6700K + iGPU.

I'm trying to find out if this thing can playback 4k videos @30/60fps smoothly. I've tested with some videos and it seems that some of them play perfectly, while others stutter sometimes.

Also, there's times where if I play the same video twice and the first time I watch it it plays perfectly, the second time there'd be a slight stutter (in some places, not constantly). Both YouTube and downloaded on the PC.

I downloaded FRAPS to see if the FPS changes when I watch videos, and the weird thing is that e.g. if the video is 4k60fps, FRAPS will always show 60fps, but my eyes would notice slight stutter from time to time.. and then I'd play the same video again and have no stutter whatsoever.

Is there a sure way to check if there are playback issues, some software?

Thank you.

geoto · March 19, 2016

They're all compressed .mp4. It's just kind of weird. I'm not running anything else but the video and it just randomly stutters. And then if I rewind it back to where it made the stutter, this time it'd be smooth. It's different every time. And I'm looking at CPU utilization, there are no spikes. Fluctuates around ~50-75% in YouTube and around 30% for the same video when played through MPC-HC.

Any idea what might cause this?

swordsm3n · March 19, 2016

Check your CPU usage while playing the videos. See if usage is maxed out when a stutter occurs, if not then it is probably a software issue.

jamesk543 · March 19, 2016

Skylake should be able to play 4K videos, provided some criteria are met. They all boil down to weather or not the fixed-function hardware decoder (IIRC, built into the iGPU) is being used.

5 hours ago, CUDA_Cores said:

it depends on what videos you are trying to play and and what file extension they use (ie mp4, mov). Uncompressed 4K video (in the MOV format) is very hard to play back on any machine, but compressed 4K video (like an mp4 video) is quite easy to play back.

Interesting point, but this is not specific enough. OP, for smoothest playback, your video must not only be compressed, but be compressed in H264 or 8-bit HEVC/H.265. These are fully supported by the hardware decoder. These compression formats can be held in containers including but not limited to .mp4 and mkv.

Now the problem is that on Youtube, video is not encoded in VP9 because VP9 allows for higher quality at lower bitrate. However, Youtube also stores the videos encoded in H.264, probably because some browsers (like Firefox) support VP9. So if you are downloading a video from Youtube, you might be downloading a video in VP9.

However, even if you download a video that is encoded in a format compatible with the Skylake hardware decoder, your playback software must use that decoder. For example, my GTX 960 has a hardware decoder that supports VP9, but Chrome does not use it, so I have relatively high CPU usage when playing 4K videos on Youtube. Anytime the hardware decoder is not used, the video will be decoded fully with software, or partially(using hardware and software). With software and partial decoding, you will see CPU usage rise as the bitrate of the video increases. Once the CPU's limit is reached, you will see performance drop. If full hardware decoding is used, CPU usage will remain very low (provided no post-processing is be performed by the playback software) and the hardware decoder will easily handle really high bitrates. Skylake's hardware decoder, IIRC, supports H.264 at resolutions up to 4K, and 8-bit HEVC/H.265 at resolutions up to 8K! However, this hardware decoder will only work with HEVC in 8-bit video, not 10-bit. I don't know about the bit depth support for H.264

In my experience, the default video player in Windows 10 (called Movies & TV or something like that) is best at taking advantage of the Skylake hardware decoder. Unfortunately, that does not allow you to measure performance. However, you can try using MPC-HC. In the internal video filter settings, which are the LAV video settings, set the decoder to DXVA2 if you want to use the hardware decoder. I have had limited success doing that. Maybe you can do better buy changing some settings. To check performance, press Ctr+J during playback of a video and look for dropped frames.

On a final note, even if you are using full software decoding, your 6700K should easily be able to process and smoothly play back 4K YouTube videos encoded in VP9. It just won't be done with as low CPU usage and power as a hardware decoder.

geoto · March 19, 2016

@jamesk543 - thanks for the information. In the video below, I haven't noticed a single stutter. I've watched it multiple times.

This one, however - sometimes it will play smoothly, and sometimes it will stutter a bit at the exact same spot, if I were to rewind it. I don't understand if this is a hardware or software issue. That's what bugs me. Why would it run perfectly 3 times, and then stutter 2 times at random places. It can't be from the video. CPU usage fluctuates between 50-75% when watching a single 4k60p video in YouTube and around 30-40% for the same video when played through MPC-HC on my computer.
It's not like I'm using anything else. I just have an antivirus on and malwarebytes, that's it. And one tab for the video in Chrome. I tried Mozilla - even worse stutter (randomly). I also tried downloading said videos to my computer and running them with MPC-HC, and again - sometimes they'll run ideally, and sometimes they'd stutter at random spots. I have no clue what's going on. I tried DVXA as per your suggestion - no change. I don't know anymore. Maybe it's drivers, maybe it's Windows 10. Could be multiple things. What's funny is that when I run FRAPS on MPC-HC, it says 60FPS, but I see the stutter. What the hell?

jamesk543 · March 19, 2016

Fraps might not be accurate for video playback. Try pressing control+J to look for dropped frames in MPC-HC. On youtube, you can right-click the video, click "stats for nerds", and look at the first number in dropped frames.

I don't have my desktop on with me right now, so I'm just testing with a Macbook Pro. I'm getting stutter in that video too, but don't see too many dropped frames in the "stats for nerds" section. It might just be a problem with the video. Try some other videos and see if you get the same problem.

50-75% CPU usage might be fine because the video is encoded in VP9. It requires more processing to decode, and on top of that, the video is 4K@60fps.

MPC-HC might have lower CPU usage because it might just be more efficient.