On reference layer and scaled reference layer offset parameters for inter-layer prediction in scalable video coding

1. A video coding method implemented in a scalable video coding system for deriving a current picture in a bitstream of coded pictures, the method comprising:

receiving a first coding layer carrying video with a base resolution,

receiving a second coding layer carrying video with an enhanced resolution having a higher resolution than the base resolution, a sample luma location xP, yP representing a position relative to a top-left sample in a current picture, said current picture is an enhancement layer picture having the enhanced resolution;

parsing the bitstream for location offset values signaled individually per reference layer picture in the first coding layer and signaled individually per enhancement layer picture in the second coding layer, the location offsets including, offsets between luma samples of a reference region in the reference layer picture and luma samples of the same reference layer picture and a corresponding enhancement layer picture, respectively; and

using the xP, yP luma location relative to a top-left luma sample of the current picture and the signaled reference layer picture and enhancement layer offset values to derive a corresponding xRef16, yRef16 luma location relative to the top-left luma sample of the reference layer picture, the luma location xRef16, yRef16 representing a luma location in the reference layer picture having the base resolution, location xRef16, yRef16 is a position in the reference layer picture relative to a top-left luma sample of the reference layer picture;

wherein the corresponding xRef16, yRef16 luma location in the reference layer picture is derived in fractional units relative to the top-left sample of the reference layer picture,

using phase shifts signaled in the bitstream to derive luma values at each of the xP, yP luma locations in the enhancement layer picture based on the luma values at each of the corresponding xRef16, yRef16 locations in the reference layer picture; and

deriving the current picture in the second coding layer.

2. The method of claim 1 , wherein the location offset values when present are signaled in a pps_multilayer_extension syntax.

3. The method of claim 1 , wherein the deriving of the current picture comprises,

a RefLayerPicWidthInSamplesY that specifies a width of the first layer picture in units of luma samples,

a RefLayerRegionWidthInSamplesY that specifies a width of the first layer reference region in units of luma samples,

wherein RefLayerRegionWidthInSamplesY=RefLayerPicWidthInSamplesY−ref_layer_left_offset−ref_layer_right_offset.

4. The method of claim 1 , wherein the deriving of the current picture comprises:

a RefLayerPicHeightInSamplesY that is equal to a height of the first layer picture in units of luma samples;

a RefLayerRegionHeightInSamplesY that is equal to a height of the first layer reference region in units of luma samples,

wherein RefLayerRegionHeightInSamplesY=RefLayerPicHeightInSamplesY−ref_layer_top_offset−ref_layer_bottom_offset.

5. The method of claim 1 , wherein the deriving of the current picture comprises,

a RefLayerPicWidthInSamplesY that specifies a width of the first layer picture in units of luma samples,

a RefLayerRegionWidthInSamplesY that specifies a width of the first layer reference region in units of luma samples; and

wherein RefLayerRegionWidthInSamplesY=RefLayerPicWidthInSamplesY−ref_layer_left_offset−ref_layer_right_offset.

6. A video coding method implemented in a scalable video coding system for deriving a current picture in a bitstream of coded pictures, the method comprising:

receiving location offset values signaled in a bitstream syntax at the picture level in said bitstream, the location offset values including:

a location offset value specifying at least one of a horizontal offset or vertical offset between a top-left luma sample of a reference region of a decoded reference picture and a top-left luma sample of said decoded reference picture, and

a location offset value specifying at least one of a horizontal offset or vertical offset between a bottom-right luma sample of a reference region of the decoded reference picture and a bottom-right luma sample of said decoded reference picture,

wherein the location offset values are signaled at the picture level for adaptability per picture, applying to all slices in the current picture for which they are signaled;

parsing the bitstream syntax to determine the location offset values applicable to all slices in the current picture for which they are signaled, using said location offset values to determine a width and height of the reference region in the decoded reference picture;

deriving an inter-layer reference picture from said decoded reference picture said derivation using the width and height of the reference region determined from said location offsets signaled in the bitstream on the picture level for deriving each of a plurality of sample values for inter-layer prediction of the inter-layer reference picture; and

deriving the current picture using the inter-layer picture.

7. The video coding method of claim 6 , wherein the location offset values when present are signaled in a pps_multilayer_extension syntax.

8. The video coding method of claim 6 , wherein a plurality of decoded reference pictures are used to derive the inter-layer reference picture.

9. The video coding method of claim 6 , wherein a corresponding sample location in the first coding layer is computed for signaling in the bitstream based on a sample location in the second coding layer.

10. The video coding method of claim 8 , wherein at least one of the one or more additional reference pictures is a reference picture from the same coding layer as the current picture.