z.lib resizers for AviSynth+

[tormento]

Originally Posted by hello_hello

I think the same applies to FMTConv

I deeply encourage you to use FMTconv when dithering down, instead of AVS+ implicits or z_img, at least for its wider dithering choices and resilience of some of them (i.e. 8) to codec encoding.

[StvG]

Originally Posted by hello_hello

StvG,

I know I asked about 32 bit float handling a while ago, but I'm still not 100% sure how to correctly convert to float and back.

For an 8 bit limited range clip, the frame property becomes full range if I do this:

ConvertBits(32)\
.z_ConvertFormat(colorspace_op="170m:601:170m=>470bg:601:470bg")\
.ConvertBits(8)

ConvertBits can change the frame property back to limited range though, and the result is exactly the same:

ConvertBits(32)\
.z_ConvertFormat(colorspace_op="170m:601:170m=>470bg:601:470bg")\
.ConvertBits(8, fulls=false, fulld=false)

However as you previously said zimg assumes 32-bit float is full range, I'm wondering if I should do it like this. According to Compare() the output isn't the same, but in my head at least, it seems to be the technically correct method. Would that assumption be correct?

Cheers.

ConvertBits(32, fulls=false, fulld=true)\
.z_ConvertFormat(colorspace_op="170m:601:170m=>470bg:601:470bg")\
.ConvertBits(8, fulls=true, fulld=false)

The latest example is the correct one.

If you will use z_ConvertFormat in already converted 32-bit environment you have to be sure that the range is [0,1] (full) before the z_ConvertFormat call.

Originally Posted by hello_hello

The output here is very close, but not exactly the same. Maybe a rounding difference when converted back to 8 bit?

A = ConvertBits(32, fulls=false, fulld=true)\
.z_ConvertFormat(colorspace_op="170m:601:170m=>470bg:601:470bg")\
.ConvertBits(8, fulls=true, fulld=false)

B = z_ConvertFormat(colorspace_op="170m:601:170m=>470bg:601:470bg", bit_depth=32)\
.z_ConvertFormat(bit_depth=8)

Compare(A,B)

Yes, the difference is due to rounding diff.