Colorspace Dataset¶

Allows you to see the impact of the color space on compression.

Download¶

mendevi download colorspace.db.xz.torrent

colorspace.json.xz (0 Mo).
colorspace.db.xz.torrent (0 Go).

Plots¶

The reference video park_joy was losslessly transcoded with different colorspaces to form the set of reference videos park_joy_*.
Each of the park_joy_* videos was lossly encoded by varying several parameters but without changing the colorspace. These videos form the sample* collection.

Distortion as a function of bitrate for several colorspaces¶

On the left, the sample videos are directly compared (without color conversion) to their lossless reference park_joy_*.
On the right, the sample videos are transformed back using the inverse color transformation and then, compared to the same reference park_joy.

mendevi plot '<colorspace.db>' -x rate -y psnr -y ssim_comp -c eotf -m '(prim, range)' -wx 'name=="park_joy"' -f 'codec!="ffv1"'

Lossless color transformation¶

The reference videos park_joy_* are transformed back using the inverse color transformation and then, compared to the same reference park_joy. In view of the PSNR, the conversion can be considered lossless.

mendevi plot '<colorspace.db>' -x rate -y psnr -c eotf -m '(prim, range)' -f 'codec=="ffv1"'

Visualize transfer functions¶

import cutcutcodec
import matplotlib.pyplot as plt
import torch
from mendevi.cst.plot import COLORS, FIGSIZE

# get curves
l2v_names: dict = {}
for name, (l2v, _) in cutcutcodec.core.colorspace.cst.TRC.items():
    l2v_names[l2v] = l2v_names.get(l2v, [])
    l2v_names[l2v].append(name)

# matplotlib plot chart
fig = plt.figure(layout="constrained", figsize=FIGSIZE)
axe = fig.subplots()
axe.grid()
fig.supylabel("v")
fig.supxlabel("l")

# plot data
l = torch.linspace(0, 1, 1000)
for i, (l2v, names) in enumerate(l2v_names.items()):
    axe.plot(l, cutcutcodec.Lambdify(l2v)(l), label=min(names), color=COLORS[i])

axe.legend()
plt.savefig("transfer.svg", format="svg")
plt.show()

Reproduce¶

for prim in bt601 bt709 bt2020
do
    for trans in linear gamma22 gamma28 smpte170m smpte2084
    do
        mendevi prepare park_joy.mkv -p fhd --primaries $prim --transfer $trans --range tv
        mendevi prepare park_joy.mkv -p fhd --primaries $prim --transfer $trans --range pc
    done
done

mendevi encode -c libx264 -c libsvtav1 reference*
mendevi probe --ref reference_park_joy_fhd.mp4 reference* sample*