Methods, systems and apparatus for electro-optical and opto-electrical conversion of images and video
The present principles are directed to a parameterized OETF/EOTF for processing images and video. The present principles provide a method for encoding a picture, comprising: applying a parameterized transfer function to a luminance (L) signal of the picture to determine a resulting V(L) transformed signal; encoding the resulting V(L); wherein the parameterized transfer function is adjusted based on a plurality of parameters to model one of a plurality of transfer functions. The present principles also provide for a method for decoding a digital picture, the method comprising: receiving the digital picture; applying a parameterized transfer function to the digital picture to determine a luminance (L) signal of the digital picture, the parameterized transfer function being based on a plurality of parameters; wherein the parameterized transfer function is adjusted based on a plurality of parameters to model one of a plurality of transfer functions.
1. A method for encoding a picture, the method comprising:
receiving a picture;
applying a parameterized transfer function to a luminance L of pixels of the picture to determine a resulting transformed luminance V(L); and
encoding the resulting transformed luminance V(L) into an encoded modified luminance picture;
outputting the encoded modified luminance picture in a bitstream;
wherein the parameterized transfer function is based on:
V
(
L
)
=
sL
n
+
c
L
n
+
st
+
m
and is adjusted based on five parameters s, n, c, t and m to model the parameterized transfer function, wherein s, n, c and t are different from zero;
wherein a parameter among the parameters allows the parameterized transfer function to determine a desired value of V(L) based on at least one selected from a group of: a smallest value of the luminance L and a highest value of the luminance L;
wherein at least one of the following describes the parameters s, n, c, t, and m:
(i) the parameters s, n, c, t, and m are encoded and signaled in a bit-stream;
(ii) the parameters s, n, c, t, and m comprise a set of pre-defined parameters of a plurality of sets of pre-defined parameters, wherein each set of the plurality of sets relates to a video content property or application;
(iii) the parameters s, n, c, t, and m are set such that V(L) is normalized to a selected range;
(iv) the parameters s, n, c, t, and m are received with the picture;
(v) the parameters s, n, c, t, and m are predefined for a certain parameter set of the parameters s, n, c, t, and m;
(vi) the parameters s, n, c, t, and m are determined for an identified Opto-Electrical Transfer Function (OETF) curve;
(vii) the parameters s, n, c, t, and m model a known luminance curve.
2. A method for decoding an encoded picture, the method comprising:
receiving the encoded picture;
decoding the encoded picture to determine a decoded picture; and
applying a parameterized transfer function to the decoded picture to determine a luminance L, the parameterized transfer function being based on:
L
(
V
)
=
(
c
-
(
V
-
m
)
st
V
-
m
-
s
)
1
/
n
and is adjusted based on five parameters s, n, c, t and m to model the parameterized transfer function, wherein s, n, c and t are all different from zero;
wherein a parameter of the plurality of parameters allows the parameterized transfer function to determine a desired value of the luminance L based on at least one selected from a group of: a smallest value of a codeword V and a highest value of the codeword V;
outputting a picture resulting from applying a parameterized transfer function to the decoded picture;
wherein at least one of the following describes the parameters s, n, c, t, and m:
(i) the parameters s, n, c, t, and m are encoded and signaled in a bit-stream;
(ii) the parameters s, n, c, t, and m comprise a set of pre-defined parameters of a plurality of sets of pre-defined parameters, wherein each set of the plurality of sets relates to a video content property or application;
(iii) the parameters s, n, c, t, and m are set such that V(L) is normalized to a selected range;
(iv) the parameters s, n, c, t, and m are received with the picture;
(v) the parameters s, n, c, t, and m are predefined for a certain parameter set of the parameters s, n, c, t, and m;
(vi) the parameters s, n, c, t, and m are determined for an identified Opto-Electrical Transfer Function (OETF) curve;
(vii) the parameters s, n, c, t, and m model a known luminance curve.
3. The method of claim 2 ,
where c=−mst, where m=V max (1+st)−s, and where u=st; and
wherein
L
(
V
)
≈
(
-
Vu
V
-
V
max
(
1
+
u
)
)
1
/
n
where Vmax, u and n are parameters, wherein an optimization algorithm is utilized to determine the parameters u and n.
4. The method of claim 3 , wherein the values of the parameters u and n are determined based on a reference curve that is based on luminance/codeword pairs (Li, Vi).
5. The method of claim 4 , wherein the values of the parameters u and n are determined by adding non-uniform weights to the luminance/codeword pairs (Li, Vi).
6. An apparatus comprising:
a processor; and
a memory, the memory storing instructions that, when executed by the apparatus, cause the apparatus to:
receive a picture;
apply a parameterized transfer function to a luminance L of pixels of the picture to determine a resulting transformed luminance V(L); and
encode the resulting transformed luminance V(L) into an encoded modified luminance picture;
output the encoded modified luminance picture in a bitstream;
wherein the parameterized transfer function is based on:
V
(
L
)
=
sL
n
+
c
L
n
+
st
+
m
and is adjusted based on five parameters s, n, c, t and m to model the parameterized transfer function, wherein s, n, c, and t are different from zero;
wherein a parameter among the parameters allows the parameterized transfer function to determine a desired value of V(L) based on at least one selected from a group of: a smallest value of the luminance L and a highest value of the luminance L;
wherein at least one of the following describes the parameters s, n, c, t, and m:
(i) the parameters s, n, c, t, and m are encoded and signaled in a bit-stream;
(ii) the parameters s, n, c, t, and m comprise a set of pre-defined parameters of a plurality of sets of pre-defined parameters, wherein each set of the plurality of sets relates to a video content property or application;
(iii) the parameters s, n, c, t, and m are set such that V(L) is normalized to a selected range;
(iv) the parameters s, n, c, t, and m are received with the picture;
(v) the parameters s, n, c, t, and m are predefined for a certain parameter set of the parameters s, n, c, t, and m;
(vi) the parameters s, n, c, t, and m are determined for an identified Opto-Electrical Transfer Function (OETF) curve;
(vii) the parameters s, n, c, t, and m model a known luminance curve.
7. An apparatus comprising:
a processor; and
a memory, the memory storing instructions that, when executed by the apparatus, cause the apparatus to:
receive the encoded picture;
decode the encoded picture to determine a decoded picture; and
apply a parameterized transfer function to the decoded picture to determine a luminance L, the parameterized transfer function being based on:
L
(
V
)
=
(
c
-
(
V
-
m
)
st
V
-
m
-
s
)
1
/
n
and is adjusted based on five parameters s, n, c, t and m to model the parameterized transfer function, wherein s, n, c and t are all different from zero;
wherein a parameter of the plurality of parameters allows the parameterized transfer function to determine a desired value of the luminance L based on at least one selected from a group of: a smallest value of a codeword V and a highest value of the codeword V;
output a picture resulting from applying a parameterized transfer function to the decoded picture;
wherein at least one of the following describes the parameters s, n, c, t, and m:
(i) the parameters s, n, c, t, and m are encoded and signaled in a bit-stream;
(ii) the parameters s, n, c, t, and m comprise a set of pre-defined parameters of a plurality of sets of pre-defined parameters,
wherein each set of the plurality of sets relates to a video content property or application;
(iii) the parameters s, n, c, t, and m are set such that V(L) is normalized to a selected range;
(iv) the parameters s, n, c, t, and m are received with the picture;
(v) the parameters s, n, c, t, and m are predefined for a certain parameter set of the parameters s, n, c, t, and m;
(vi) the parameters s, n, c, t, and m are determined for an identified Opto-Electrical Transfer Function (OETF) curve;
(vii) the parameters s, n, c, t, and m model a known luminance curve.
8. The apparatus of claim 7 ,
where c=−mst, where m=V max (1+st)−s, and where u=st; and
wherein
L
(
V
)
≈
(
-
Vu
V
-
V
max
(
1
+
u
)
)
1
/
n
where Vmax, u and n are parameters, wherein an optimization algorithm is utilized to determine the parameters u and n.