Compression Artifacts

[nfv]

What do you guys use to help reduce compression artifacts?

I've tried deblock and I honestly see no difference at all. Maybe I'm not using it right?

I have a lot of captures sourced from satellite TV with lots of compression artifacts.

Thanks!

[FranceBB]

Deblock can be quite effective against starved images suffering from blocking artifacts.
If you are re-encoding using x264 or x265 you can use the built-in deblock filter which is quite good: positive values are more aggressive, negative values are less aggressive.
You can try by setting it really high and then lower it down 'till you'll find the sweet spot.
There are also deblocking plugins for Avisynth, like Deblock_QED, Unbloc etc, but it's really up to what you gotta do.

As a side note: please note that once the quantizer cut off important values, there's no way you can get them back, so although the picture will look "nicer" than a blocky one, it's gonna be blurry.

[johnmeyer]

There are many tricks to getting clean encodes with minimal artifacts.

1. Do light noise reduction (although resist the urge to do too much: never over-do NR) before encoding.

2. Get rid of any pulldown. I learned this twenty years ago when doing SVCD encodes. At those low bitrates and crude encoding, artifacts could be huge. IVTC made the most massive reduction in compression artifacts of anything I've ever done.

3. Do multi-pass encoding. This too is really important when doing low bitrate encodes. High bitrates should not exhibit significant compression artifacts, and if you are getting artifacts when using high bitrates, you are doing something wrong.

4. Use a good encoder. With every type of video compression, there can be massive differences between encoders. Back when MPEG-2 was the big thing, the cheap encoders were really quite awful, and the professional codecs ran circles around them. These days, the open source encoders are actually pretty good, but there still can be differences.

[Cary Knoop]

I have a lot of captures sourced from satellite TV with lots of compression artifacts.

Did you capture with a too low bitrate or were the compression artifacts already in the TV stream?

[Boulder]

Sometimes excessive ugly compression artifacts can be hidden by applying artificial noise on the image and then denoising slightly if required. It can create a layer of fake detail to fool your brain. Something like GrainFactory3 could be useful here.

[Mounir]

I use this script:


MPEG2Source("video.d2v", cpu=0,info=3)

# deblocking interlaced video with Deblock_QED:
par=getparity()
SeparateFields().PointResize(width,height)
Deblock_QED(24,28,uv=3)
AssumeFrameBased()
SeparateFields()
Merge(SelectEven(),SelectOdd())
par ? AssumeTFF() : AssumeBFF()
Weave()


# Noise reduction (for interlaced video)

c=last
#even fields
# Motion compensation on frames -2...+2
even = c.SeparateFields().SelectEven()
super_even=even.MSuper()
vf2 = super_even.MAnalyse (isb=false, delta=2, overlap=4)
vf1 = super_even.MAnalyse (isb=false, delta=1, overlap=4)
vb1 = super_even.MAnalyse (isb=true, delta=1, overlap=4)
vb2 = super_even.MAnalyse (isb=true, delta=2, overlap=4)
cf2 = MCompensate (even, super_even, vf2, thSAD=400)
cf1 = MCompensate (even, super_even, vf1, thSAD=400)
cb1 = MCompensate (even, super_even, vb1, thSAD=400)
cb2 = MCompensate (even, super_even, vb2, thSAD=400)
# dfttest on motion-compensated clip
Interleave (cf2, cf1, even, cb1, cb2)
RemoveSpotsMC()
dfttest (sigma=4, sigma2=4, tbsize=5, lsb=false)
SelectEvery (5, 2)
# Gradient smoothing
presmooth = last
#SmoothGrad (radius=20, thr=0.15) #
#SmoothGrad (radius=12, thr=0.25, ref=presmooth)#
# Back to 8 bits, ordered dithering
#DitherPost () #
filtered_even=last
#odd fields
# Motion compensation on frames -2...+2
odd = c.SeparateFields().SelectOdd()
super_odd=odd.MSuper()
vf2 = super_odd.MAnalyse (isb=false, delta=2, overlap=4)
vf1 = super_odd.MAnalyse (isb=false, delta=1, overlap=4)
vb1 = super_odd.MAnalyse (isb=true, delta=1, overlap=4)
vb2 = super_odd.MAnalyse (isb=true, delta=2, overlap=4)
cf2 = MCompensate (odd, super_odd, vf2, thSAD=400)
cf1 = MCompensate (odd, super_odd, vf1, thSAD=400)
cb1 = MCompensate (odd, super_odd, vb1, thSAD=400)
cb2 = MCompensate (odd, super_odd, vb2, thSAD=400)
# dfttest on motion-compensated clip
Interleave (cf2, cf1, odd, cb1, cb2)
RemoveSpotsMC()
dfttest (sigma=4, sigma2=4, tbsize=5, lsb=false)
SelectEvery (5, 2)
# Gradient smoothing
presmooth = last
#SmoothGrad (radius=20, thr=0.15) #
#SmoothGrad (radius=12, thr=0.25, ref=presmooth)#
# Back to 8 bits, ordered dithering
#DitherPost ()#
filtered_odd=last
Interleave(filtered_even, filtered_odd)
weave()