Multimedia device for processing video signal and control method thereof
The present invention discloses a multimedia device for processing a video signal and control method thereof. According to an embodiment of the present invention, the multimedia device includes a controller configured to perform tone mapping, a dynamic contrast function, and a local contrast function. The controller performs the tone mapping not only on an HDR video signal but also on an SDR video signal. When performing the tone mapping on the SDR video signal, the controller amplifies only an intermediate-gradient region without adjusting low-gradient and high-gradient regions. When performing the dynamic contrast function, the controller only an intermediate-gradient region of the video signal without adjusting low-gradient and high-gradient regions. When performing the local contrast function, the controller divides the video signal into blocks, calculates an APL value of each block, and then applies a linear curve based on the APL value.
1. A multimedia device for processing a video signal, the multimedia device comprising:
a memory;
a receiving unit configured to receive a video signal; and
a controller configured to:
perform, by referring to the memory, a first tone mapping on the received video signal by applying a first linear curve to the received video signal based on a determination that the received video signal corresponds to a high dynamic range (HDR) video signal;
perform, by referring to the memory, a second tone mapping on the received video signal by
applying a non-linear curve amplifying a second gradient of the received video signal and applying a second linear curve to a first gradient region and a third gradient region of the received video signal based on a determination that the received video signal corresponds to a standard dynamic range (SDR) video signal, wherein the non-linear curve is different from the first linear curve and the second linear curve, wherein the second gradient region is a signal region higher than the first gradient region, and the third gradient region is a signal region higher than the second gradient region and the first gradient region, the second gradient region, and the third gradient region do not overlap with each other; and
perform a dynamic contrast function on the second tone mapped received SDR video signal based on the determination that the received video signal corresponds to the SDR video signal by applying different curves based on a gradient region of each of the first tone mapped HDR received video signal and the second tone mapped SDR received video signal, wherein the first tone mapping and the second tone mapping are performed in a first color space and the dynamic contrast function is performed in a second color space that is different from the first color space; and
perform the dynamic contrast function on the first tone mapped HDR received video signal based on the determination that the received video signal corresponds to the HDR video signal.
2. The multimedia device of claim 1 , wherein the controller is configured to:
perform different hue and saturation preserving on each of the HDR video signal and the SDR video signal.
3. The multimedia device of claim 1 , wherein the controller is further configured to perform a local contrast function, and wherein in the local contrast function, different curves are applied based on an average picture level (APL) value of each of the HDR video signal and the SDR video signal.
4. The multimedia device of claim 3 , wherein performing the local contrast function, comprises:
divide the HDR video signal or the SDR video signal into virtual blocks;
calculate an APL value for each of the virtual blocks; and
apply a linear curve to each of the virtual blocks based on the calculated APL value.
5. The multimedia device of claim 1 , wherein the color space for the first tone mapping and the second tone mapping is an RGB color space.
6. The multimedia device of claim 1 , wherein performing the dynamic contrast function, comprises:
output a fourth gradient region and a sixth gradient region of an original signal as it is; and
apply a curve amplifying the original signal to a fifth gradient region,
wherein the fourth to sixth regions do not overlap with each other, and
wherein the fifth gradient region is a signal region higher than the fourth gradient region, and the sixth gradient region is a signal region higher than the fifth gradient region.
7. A method performed by a multimedia device for processing a video signal, the method comprising:
receiving a video signal;
performing a first tone mapping on the received video signal by applying a first linear curve to the received video signal based on a determination that the received video signal corresponds to a high dynamic range (HDR) video signal;
performing a second tone mapping on the received video signal by applying a non-linear curve amplifying a second gradient region of the received video signal and applying a second linear curve to a first gradient region and a third gradient region of the received video signal based on a determination that the received video signal corresponds to a standard dynamic range (SDR) video signal, wherein the non-linear curve is different from the first linear curve and the second linear curve, wherein the second gradient region is a signal region higher than the first gradient region, and the third gradient region is a signal region higher than the second gradient region and the first gradient region, the second gradient region, and the third gradient region do not overlap with each other;
performing a dynamic contrast function on the second tone mapped received SDR video signal based on the determination that the received video signal corresponds to the SDR video signal by applying different curves based on a gradient region of each of the first tone mapped HDR received video signal and the second tone mapped SDR received video signal, wherein the first tone mapping and the second tone mapping are performed in a first color space and the dynamic contrast function is performed in a second color space that is different from the first color space; and
performing the dynamic contrast function on the first tone mapped HDR received video signal based on the determination that the received video signal corresponds to the HDR video signal.
8. The method of claim 7 , wherein different hue and saturation preserving is performed in each of the first and second tone mapping.
9. The method of claim 7 , further comprising performing a local contrast function, and wherein in the local contrast function, different curves are applied based on an average picture level (APL) value of each of the HDR video signal and the SDR video signal.
10. The method of claim 9 , wherein performing the local contrast function further comprises:
dividing the HDR video signal or the SDR video signal into virtual blocks;
calculating an APL value for each of the virtual blocks; and
applying a linear curve to each of the virtual blocks based on the calculated APL value.
11. The method of claim 7 , wherein the color space for the first tone mapping and the second tone mapping is an RGB color space.
12. The method of claim 7 , wherein performing the dynamic contrast function comprises:
outputting a fourth gradient region and a sixth gradient region of an original signal as it is; and
applying a curve amplifying the original signal to a fifth gradient region,
wherein the fourth to sixth regions do not overlap with each other, and
wherein the fifth gradient region is a signal region higher than the fourth gradient region, and the sixth gradient region is a signal region higher than the fifth gradient region.