How To Use Mpeg4 AVC Deblocking Effectively (Small FAQ)

[jellysandwich]

Would someone mind posting a few screenshot examples? I tried doing a test on a small clip, but I can't really tell any differences... I think I'm picking bad scenes or something.

js

[akupenguin]

http://forum.doom9.org/showthread.ph...115#post689115

[lovelove]

Originally Posted by *.mp4 guy

...Threshold Parameter refers to Beta Deblocking (Alpha and Beta Deblocking are the official names). [...]

Lower values of Beta Deblocking apply less deblocking to more flat blocks with details present (but more deblocking to blocks without details), while Higher values cause more deblocking to be applied to less flat blocks with details present.

If beta deblocking is indeed a treshold parameter, then your abovementioned explanation is wrong. A treshold is not gradual but a specific level/value dividing the basic set in two subsets: all values below the treshold and all values above the treshold. Now given a function with 2 parameters (strength and threshold), 'strength' will be applied to all values below (or above) the threshold.

Thus the correct explanation is (assuming the parameters work as you describe, which I have NOT tested in practice):

Deblocking is applied with alpha strength to blocks with less detail than the (beta) threshold. 

Therefore:
The higher the alpha parameter, the higher the deblocking strength applied.
The higher the beta parameter, the more blocks are deblocked (namely with strength alpha).

PS: In order for your explanation to be more correct, you would have to replace all red words above (i.e. "less deblocking" and "more deblocking") by "deblocking with alpha strength". But then you are still contradicting yourself when saying "to more flat blocks with details present" vs. "to less flat blocks with details present". So I would stick to my shorter and correct version ;-)

EDIT: having read the remainder of the thread, I add that DarkZell666 gives the same (correct) explanation.

[infoeater]

Originally Posted by *.mp4 guy

(...)more flat blocks with details present(...)

Is it antagonism or deblocking filter has some other method to measure amount of details then flatness?

[asarian]

Does --deblock require the existence of conventional block sizes (like 8x8) to work properly? Or does it work as effectively on upscaled material too? (with still some visible blocking, but with what would now be larger, non-standard block sizes).

Thanks.

[Andouille]

Originally Posted by asarian

Does --deblock require the existence of conventional block sizes (like 8x8) to work properly? Or does it work as effectively on upscaled material too? (with still some visible blocking, but with what would now be larger, non-standard block sizes).

Thanks.

x264's "deblock" does not filter your blocky source. It is a part of the encoding.
So resolution does not matter.

[asarian]

Originally Posted by Andouille

x264's "deblock" does not filter your blocky source. It is a part of the encoding.
So resolution does not matter.

Not sure I fully understand the answer. Obviously x264 does deblocking on what invariably takes my source for input, right?

Or are you saying it does not look at the source per se to deblock, but just generally deblocks on what it encodes? (Which would still leave me with a deblocked movie, right?)

[detmek]

X264 divides image into diferent block sizes, 16x16, 8x8, 4x4. Internal deblocking deblocks these macroblocks to prevent hard edges between those, and in general to prevent blocking as a result of encoding. It also removes a bit of details and makes picture softer when used with higher values. It does not remove blocking from source. Usd avisynth deblock or unblock plugin if you want to deblock source.
Read first post for more detailed explanation.

[asarian]

Originally Posted by detmek

X264 divides image into diferent block sizes, 16x16, 8x8, 4x4. Internal deblocking deblocks these macroblocks to prevent hard edges between those, and in general to prevent blocking as a result of encoding. It also removes a bit of details and makes picture softer when used with higher values. It does not remove blocking from source. Usd avisynth deblock or unblock plugin if you want to deblock source.
Read first post for more detailed explanation.

Ah, thank you! It's a lot more clear now.

[Thunderbolt8]

what are the deblocking effects on encoding speed? is it logical to assume that the lowest values -3;-3 are fastest, because the least amount of deblocking is applied then?

[foxyshadis]

Depends on high low your crf and how high your rd level is. The more blocks with quants below or barely above the deblocking threshold, the less get deblocked. The higher your rd level, the more times each block is checked, so the more helpful less deblocking is. Any benchmarks will be heavily weighted toward the video and settings you use, but will be a rather small part of the overall speed.

You can actually go all the way down to -6,-6, at which point you might as well just turn deblocking off completely.

[Lathe]

Sort of along the topic of this thread...

If I lower the deblock settings and slightly raise the Psy Trellis, this is pretty much encoding at high bitrates with Blu-rays using a CRF around 20 and x264 settings around 'Slow', does that increase the amount of bitrate used and thus increase the file size?

Say I use a setting of --deblock -3:-3 --psy-rd 1.00:0.25, will this inherently raise the amount of bitrate 'needed' while encoding and thus increase the overall resulting file size?

Thanks!

***EDIT

Hmmm, well, I THINK I got the answer to my question here from reading a few more threads. Apparently, YES, the bitrate will indeed go up even using --tune film according to other threads, so -3, -3 AND raising the Psy Trellis is BOUND to increase it even more, I guess...

I was bloody wondering WHY my encodes were coming out so big...

[Kill3rWolf]

Originally Posted by Lathe

Sort of along the topic of this thread...

If I lower the deblock settings and slightly raise the Psy Trellis, this is pretty much encoding at high bitrates with Blu-rays using a CRF around 20 and x264 settings around 'Slow', does that increase the amount of bitrate used and thus increase the file size?

Say I use a setting of --deblock -3:-3 --psy-rd 1.00:0.25, will this inherently raise the amount of bitrate 'needed' while encoding and thus increase the overall resulting file size?

Thanks!

***EDIT

Hmmm, well, I THINK I got the answer to my question here from reading a few more threads. Apparently, YES, the bitrate will indeed go up even using --tune film according to other threads, so -3, -3 AND raising the Psy Trellis is BOUND to increase it even more, I guess...

I was bloody wondering WHY my encodes were coming out so big...

Could you explain more about how you got your answers & your test results? What about animation film x265 encoding? Deblock=1:-3:-3 can be used?

[benwaggoner]

Originally Posted by Kill3rWolf

Could you explain more about how you got your answers & your test results? What about animation film x265 encoding? Deblock=1:-3:-3 can be used?

Note the post you responded to was nearly 5 years ago.