On reference layer and scaled reference layer offset parameters for inter-layer prediction in scalable video coding
A process for determining the selection of filters and input samples is provided for scalable video coding. The process provides for re-sampling using video data obtained from an encoder or decoder process of a base layer (BL) in a multi-layer system to improve quality in Scalable High Efficiency Video Coding (SHVC). In order to provide better alignment between layers, it is proposed that reference layer offset adjustment parameters be signaled.
1. A video coding method implemented in a scalable video coding system for decoding a current picture in a bitstream of coded pictures, the method comprising:
(a) receiving a first coding layer carrying video with a base resolution;
(b) 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;
(c) 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;
(d) 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;
(e) 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;
(f) 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;
(g) decoding 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 decoding 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
RefLayerRegionWidthInSamples Y =RefLayerPicWidthInSamples Y −ref_layer_left_offset−ref_layer_right_offset.
4. The method of claim 1 , wherein the decoding 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
RefLayerRegionHeightInSamples Y =RefLayerPicHeightInSamples Y −ref_layer_top_offset−ref_layer_bottom_offset.
5. The method of claim 1 , wherein the decoding 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
RefLayerRegionWidthInSamples Y =RefLayerPicWidthInSamples Y −ref_layer_left_offset−ref_layer_right_offset.