Help with blocks on H264

[jolumatro]

Hello everyone!

Im currently encoding a lot with Intel QuickSync, and I've come to notice a lot the blocking artifacts on black colors, I almost cannot take it.

On the other hand, I cannot switch to software encoding, as my Intel Atom quad-core is not powerful enough to make BD->AVCHD in realistic times, or BD->720p mp4, that is what I used to do with a more powerful PC.

What would be the H264 parameter that controls or influences those blocking artifacts the most? Bitrate does not count

Thank you very much in advance.

PS: Sorry I cannot provide a screenshot ATM

[LigH.de]

There are only two ways to avoid blocking: Either a more efficient encoder, or more bitrate. You don't want either.

Reminds me of overweight people who would do anything to lose weight. Except hunger or sports. There must be a miracle ...

[jolumatro]

Thanks for the answer

I get it, but my situation is pretty concrete, I really cannot upgrade anything in this laptop, and software takes forever as in not practical.

Let me show you a couple of samples


[Attachment 44760 - Click to enlarge]
[Attachment 44761 - Click to enlarge]

Notice the black blocks in the darker areas. Surely some parameter could help with that, no? Im talking x264 straight, not precisely Quick Sync.

I gotta say, for the rest, QS does a pretty good job.

Thanks

[hello_hello]

It's harder to tell when the pictures aren't moving, but how obvious does the blocking look to everyone else?

Displaying the screenshots on my Plasma, I can barely see the blocking. There's obviously plenty of it, because I can see it when I adjust the luminance levels, but using my normal configuration on the TV (which admittedly I calibrated by sight), it doesn't stand out too much because it's almost black. Maybe it's more noticable when the pictures are moving.

jolumatro, do the encodes look really blocky when viewing them on a TV or is it just the laptop? I'm wondering how much of it is displaying video with the wrong luminance levels, or using a laptop display with crap black levels etc.

[jolumatro]

Thanks for the answer.

The laptop is connected to a 24' Samsung TV, where I check the encodes. I have not calibrated it per se, and the blocking in movement becomes apparent. The laptop itself does a good job, but it's just a 11,6" HD Ready display. A 5" 1280x720 phone also does not show anything, but it's scaled down.

[poisondeathray]

Im talking x264 straight, not precisely Quick Sync.

For x264, increasing the aq strength will improve distribution to those areas; but if you use crf encoding, it will increase the bitrate at a given crf value . If you used multipass encode, then at the same bitrate, you will notice improvement there, but at the expense of edge quality . You can also try some of the other aq modes, but I think mode 1 is the most balanced. In the end you're still going to need more bitrate if you want to keep picture quality same, but just increase the dark area quality. It's just that if you tweak some of the settings, you might not need as much extra bitrate to get the result you want.

NVenc has AQ options(but they mostly run on CPU, slows down encoding speed immensely), but I don't think QSV does

[hello_hello]

Thanks for the answer.

The laptop is connected to a 24' Samsung TV, where I check the encodes. I have not calibrated it per se, and the blocking in movement becomes apparent. The laptop itself does a good job, but it's just a 11,6" HD Ready display. A 5" 1280x720 phone also does not show anything, but it's scaled down.

If you have a Bluray player connected to the TV and you compare the original Bluray video to the encoded version and it looks the same (black isn't dark grey rather than black etc) then that won't be the problem, but it might be worth checking.

The TV could have a deblocking filter. I think for Samsung the filter can be configured for each inout. My Samsung Plasma has two filters called Noise Filter and MPEG Filter (I think) under Advanced picture options. If I remember correctly, "MPEG filter" is Samsung-speak for deblocking. If you crank it up it'll probably blur the picture a little, but it might help, assuming your TV has the same options.

[jolumatro]

Im talking x264 straight, not precisely Quick Sync.

For x264, increasing the aq strength will improve distribution to those areas; but if you use crf encoding, it will increase the bitrate at a given crf value . If you used multipass encode, then at the same bitrate, you will notice improvement there, but at the expense of edge quality . You can also try some of the other aq modes, but I think mode 1 is the most balanced. In the end you're still going to need more bitrate if you want to keep picture quality same, but just increase the dark area quality. It's just that if you tweak some of the settings, you might not need as much extra bitrate to get the result you want.

NVenc has AQ options(but they mostly run on CPU, slows down encoding speed immensely), but I don't think QSV does

Thank you so much! Ive been trying to find that precisely, if QSV has that parameter, so far no luck. But that's the answer I was looking for.

[jolumatro]

Thanks for the answer.

The laptop is connected to a 24' Samsung TV, where I check the encodes. I have not calibrated it per se, and the blocking in movement becomes apparent. The laptop itself does a good job, but it's just a 11,6" HD Ready display. A 5" 1280x720 phone also does not show anything, but it's scaled down.

If you have a Bluray player connected to the TV and you compare the original Bluray video to the encoded version and it looks the same (black isn't dark grey rather than black etc) then that won't be the problem, but it might be worth checking.

The TV could have a deblocking filter. I think for Samsung the filter can be configured for each inout. My Samsung Plasma has two filters called Noise Filter and MPEG Filter (I think) under Advanced picture options. If I remember correctly, "MPEG filter" is Samsung-speak for deblocking. If you crank it up it'll probably blur the picture a little, but it might help, assuming your TV has the same options.

My TV does not have those settings, but it would be nice to test in another screen, I might have a change to do that this weekend. Thanks for the tip.

[pandy]

Check input and output quantization range and check if they are properly signalled in bitstream. Perhaps black level is elevated by TV and blocking is exaggerated. I would also check QSV manuals on psy tuning - perhaps insufficient (too high quantizer) bitrate is allocated for dark areas - this is common issue for poor psy tuning.