1080p vs 2160p which source should we use for encoding

[iKron]

lets say 1080p x264 file size is 3GB and 2160p x265 file size is 6GB. i know it's kind of foolish question because both file has different encode settings and codec. but in general which source should i use if i want to use for encode in x265 1080p resolution?

is there any common rule like if a x264 1080p size is X, then normally A x265 2160p size will be preferably Y? in terms of math calculation. not going for encode settings etc.

[Selur]

.. in general which source should i use if i want to use for encode in x265 1080p resolution?
Whatever source looks better.
is there any common rule like if a x264 1080p size is X, then normally A x265 2160p size will be preferably Y?
No.

[FranceBB]

lets say 1080p x264 file size is 3GB and 2160p x265 file size is 6GB. i know it's kind of foolish question because both file has different encode settings and codec. but in general which source should i use if i want to use for encode in x265 1080p resolution?

We have too little info, so I'm gonna make a few assumptions.
I assume both the FULL HD and the UHD sources are 4:2:0, but the FULL HD one is 8bit and the UHD one is 10bit planar.
Here's an interesting idea: unless you have hardware compatibility in mind (i.e BD players etc), you can do the following

Step A) Index the 3840x2160 4:2:0 UHD 10bit source in Avisynth

Step B) Downscale the luma to 1920x1080 but leave the chroma as it is (given that it's 4:2:0 it will be 1920x1080)

Step C) Merge the downscaled luma with the original chroma

Step D) Encode with x265 to get a glorious FULL HD 10bit 4:4:4 with full chroma resolution.

You're welcome

;)


EDIT: Not my best script, but assuming the UHD source is BT709 SDR


UHD 4:2:0 yv12 planar to FULL HD 4:4:4 yv24
### You need to take care of chroma alignment yourself!! ###
### For 4:2:0 MPEG-2 classic top-left src_left=-0.50, src_top=0 ###

Y = ConvertToY8(matrix="Rec709").SincResize(1920, 1080, src_left=-0.50, src_top=0)
U = UToY8()
V = VToY8()
YToUV(U, V, Y)

[jpsdr]

I suggest instead the following for high bits :

video= "your source filter High bit depth 4:2:0"
Y=PlaneToY(video,"Y").SincResize(1920, 1080, src_left=-0.50, src_top=0)
U=PlaneToY(video,"U")
V=PlaneToY(video,"V")
YtoUV(U,V,Y)

[benwaggoner]

That said, 4:4:4 chroma isn't really going to make a visible difference in natural continuous-tone images. It's most useful for things like screen recordings and highly saturated text with tapered serifs.

[RanmaCanada]

Leave them both as is, because if they are more than an hour long, they are seriously bitstarved.

[FranceBB]

That said, 4:4:4 chroma isn't really going to make a visible difference in natural continuous-tone images.

Well but it's nice to have for free given that he's gonna downscale to FULL HD anyway and that monitors are RGB so the chroma must match luma anyway and this way it won't be downscaled in encoding and upscaled in playback but it will stay as is instead. That being said, call me crazy but while modern TVs do their fair share of processing with fairly good chroma upscaling on live feeds, when I'm watching something live on my computer and I can't go through a proper player and I have to rather use a browser like chrome (BBC iPlayer, ITV Hub, All 4, 5 USA, CBS etc) chroma is upscaled with point resize / nearest neighbour and I can see it, especially on red surfaces.

[Boulder]

I think that a bigger problem with chroma is that x265 destroys the red component, no matter if you use a heavily negative QP offset or whatever. I guess it does the same to blue as well but it's much more difficult to see.

[SaurusX]

I think that a bigger problem with chroma is that x265 destroys the red component, no matter if you use a heavily negative QP offset or whatever. I guess it does the same to blue as well but it's much more difficult to see.

Why is this true? I've noticed that when encoding some 1080p material in x265 the red chroma is extremely aliased. I thought I was doing something wrong, but is this just something to be expected if using x265?

[Boulder]

This is an old problem with x265 and cannot be avoided. I doubt it will ever be fixed since the project has been inactive for so long already.

[Forteen88]

This is an old problem with x265 and cannot be avoided. I doubt it will ever be fixed since the project has been inactive for so long already.So is MainConcept's HEVC/H.265 encoder better? It got a better score at MSU's test.

[kolak]

Ateme may be better.