Scalable video encoding/decoding method and apparatus
Provided is a video decoding apparatus including an encoding information obtainer configured to obtain, from a bitstream, reference layer size information, reference layer offset information, current layer size information, and current layer offset information, a scale ratio determiner configured to determine a scale ratio indicating a difference between a size of a reference area and a size of an expanded reference area, according to the size of the reference area which is determined from the reference layer size information and the reference layer offset information and the size of the expanded reference area which is determined from the current layer size information and the current layer offset information, and an up-sampling unit configured to determine the expanded reference area by up-sampling the reference area according to the reference layer offset information, the current layer offset information, and the scale ratio.
1. A video decoding apparatus comprising:
a memory storing instructions; and
one or more processors configured to execute the stored instructions to:
obtain, from a bitstream, reference layer size information indicating a height and width of a reference layer picture, reference layer offset information to define a reference area used in inter-layer prediction from the reference layer picture, current layer size information indicating a height and width of a current layer picture, and current layer offset information to define, from the current layer picture, an expanded reference area corresponding to the reference area,
modify reference layer offset information and current layer offset information according to a color index of the reference layer picture and the current layer picture,
determine a scale ratio indicating a ratio of a size of the reference area to a size of the expanded reference area, according to the size of the reference area which is determined from the reference layer size information and the reference layer offset information, and the size of the expanded reference area which is determined from the current layer size information and the current layer offset information, and
determine the expanded reference area by up-sampling the reference area according to the reference layer offset information, the current layer offset information, and the scale ratio.
2. The video decoding apparatus of claim 1 , wherein
the reference layer offset information comprises a reference layer left offset, a reference layer right offset, a reference layer top offset, and a reference layer bottom offset.
3. The video decoding apparatus of claim 2 , wherein
the reference layer left offset is a horizontal offset between a sample in an upper left area of the reference layer picture and a sample in an upper left area of the reference area,
the reference layer top offset is a vertical offset between the sample in the upper left area of the reference layer picture and the sample in the upper left area of the reference area,
the reference layer right offset is a horizontal offset between a sample in a lower right area of the reference layer picture and a sample in a lower right area of the reference area, and
the reference layer bottom offset is a vertical offset between the sample in the lower right area of the reference layer picture and the sample in the lower right area of the reference area.
4. The video decoding apparatus of claim 2 , one or more processors configured to execute further instructions to: determine a height of the reference area by subtracting the reference layer top offset and the reference layer bottom offset from the height of the reference layer picture, and
determine a width of the reference area by subtracting the reference layer right offset and the reference layer left offset from the width of the reference layer picture.
5. The video decoding apparatus of claim 1 , wherein the one or more processors generate a prediction image with respect to the current layer picture based on the expanded reference area.
6. A video decoding method performed by a processor comprising:
obtaining, by the processor, from a bitstream, reference layer size information indicating a height and width of a reference layer picture, reference layer offset information to define a reference area used in inter-layer prediction from the reference layer picture, current layer size information indicating a height and width of a current layer picture, and current layer offset information to define, from the current layer picture, an expanded reference area corresponding to the reference area;
modifying, by the processor, reference layer offset information and current layer offset information according to a color index of the reference layer picture and the current layer picture;
determining, by the processor, a scale ratio indicating a ratio of a size of the reference area to a size of the expanded reference area, according to the size of the reference area which is determined from the reference layer size information and the reference layer offset information, and the size of the expanded reference area which is determined from the current layer size information and the current layer offset information; and
determining, by the processor, the expanded reference area by up-sampling the reference area according to the reference layer offset information, the current layer offset information, and the scale ratio.
7. The video decoding method of claim 6 , wherein the reference layer offset information comprises a reference layer left offset, a reference layer right offset, a reference layer top offset, and a reference layer bottom offset.
8. The video decoding method of claim 6 , wherein
the reference layer left offset is a horizontal offset between a sample in an upper left area of the reference layer picture and a sample in an upper left area of the reference area,
the reference layer top offset is a vertical offset between the sample in the upper left area of the reference layer picture and the sample in the upper left area of the reference area,
the reference layer right offset is a horizontal offset between a sample in a lower right area of the reference layer picture and a sample in a lower right area of the reference area, and
the reference layer bottom offset is a vertical offset between the sample in the lower right area of the reference layer picture and the sample in the lower right area of the reference area.
9. The video decoding method of claim 6 , wherein the determining of the size of the reference area comprises determining a height of the reference area by subtracting the reference layer top offset and the reference layer bottom offset from the height of the reference layer picture, and determining a width of the reference area by subtracting the reference layer right offset and the reference layer left offset from the width of the reference layer picture.
10. The video decoding method of claim 6 , further comprising generating, by the processor, a prediction image with respect to the current layer picture based on the expanded reference area.
11. A non-transitory computer-readable recording medium having recorded thereon a program for executing, by a processor, the video decoding method of claim 6 .