Scalable video coding using reference and scaled reference layer offsets
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 accommodate other applications such as interlace/progressive scalability and to increase the resolution of the alignment between layers, it is proposed that the phase offset adjustment parameters be signaled.
1. A video coding method for deriving a current picture implemented in a system for scalable video coding, said method comprising:
determining whether scaled offsets and phase shifts are present in one or more syntax structures at a picture level;
parsing the one or more picture level syntax structures to determine the scaled offsets and phase shifts for deriving an inter-layer reference picture, wherein the scaled offsets and phase shifts signaled in syntax elements at the picture level are adaptive per picture and applicable to all slices in the inter-layer reference picture for which they are signaled;
deriving the inter-layer reference picture from a decoded reference picture using the scaled offsets and phase shifts, wherein the decoded reference picture is in a first coding layer in a plurality of coding layers and the inter-layer reference picture is in a second coding layer in the plurality of coding layers,
the derivation including a prediction of a value at a pixel location in the second coding layer based on a corresponding value at a pixel location in the first coding layer in the plurality of coding layers;
the derivation including use of the scaled offsets, that specify offsets between a first picture sample in the inter-layer reference picture in the second coding layer that is collocated with a picture sample of the decoded reference picture in the first coding layer and a second picture sample of the inter-layer reference picture in the second coding layer, the scaled offsets between said first and second picture samples in the inter-layer reference picture for adjusting the predicted value pixel location; and
deriving the current picture using the inter-layer reference picture including the predicted value at the adjusted predicted value pixel location.
2. The method of claim 1 , wherein the scaled offsets are signaled in a pps_multilayer_extension syntax that is conditional on a pps_extension_type_flag[1] flag.
3. The method of claim 1 , wherein the scaled offsets are signaled conditional on a scaled_reference_offset_present_flag flag.
4. The method of claim 1 , wherein at least one of the scaled offsets specifies a horizontal component of the at least one of the scaled offsets.
5. The method of claim 1 , wherein at least one of the scaled offsets specifies a vertical component of the at least one of the scaled offsets.
6. The method of claim 1 ,
wherein at least one of the scaled offsets specifies an offset between a picture sample in the inter-layer reference picture that is collocated with a bottom-right picture sample of the decoded reference picture in the first coding layer and a corresponding bottom-right picture sample of the inter-layer reference picture in the second layer coding for adjustment of said predicted value pixel location.
7. The method of claim 5 , wherein a scaled_ref_layer_top_offset syntax element and/or a scaled_ref_layer_bottom_offset syntax element specifies the vertical component of the at least one of the scaled offsets.
8. The method of claim 4 , wherein a scaled_ref_layer_left_offset syntax element and/or a scaled_ref_layer_right_offset syntax element specifies the horizontal component of the at least one of the scaled offsets.
9. The method of claim 1 , wherein at least one of the scaled offsets specifies an offset between the picture sample in the inter-layer reference picture that is collocated with a top-left picture sample of the decoded reference picture in the first coding layer and a corresponding top-left picture sample of the inter-layer reference picture in said second coding layer.
10. The method of claim 4 , wherein the at least one of the scaled offsets specifies a horizontal offset between the picture sample in the inter-layer reference picture that is collocated with a top-left picture sample of the reference picture in the first coding layer and a corresponding top-left picture sample of the inter-layer reference picture in said second coding layer.
11. The method of claim 5 ,
wherein the at least one of the scaled offsets specifies a vertical offset between the picture sample in the inter-layer reference picture that is collocated with a top-left picture sample of the decoded reference picture in the first coding layer and a corresponding top-left sample of the inter-layer reference picture in said second coding layer.
12. The method of claim 4 , wherein the at least one of the scaled offsets specifies a horizontal offset between the picture sample in the inter-layer reference picture that is collocated with a bottom-right picture sample of the decoded reference picture in the first coding layer and a corresponding bottom-right picture sample of the second coding layer for adjustment of said predicted value pixel location.
13. The method of claim 5 , wherein the at least one of the scaled offsets specifies a vertical offset between the picture sample in the inter-layer reference picture that is collocated with a bottom-right picture sample of the decoded reference picture in the first coding layer and a corresponding bottom-right picture sample of the second coding layer for adjustment of said predicted value pixel location.
14. The method of claim 1 , wherein the one or more syntax structures are signaled in a picture parameter set (PPS) syntax.
15. The method of claim 1 ,
wherein at least one of the phase shifts signaled at the picture level specifies a phase shift used in a resampling process.
16. The method of claim 15 , wherein the at least one of the offset phase shifts is signaled in a pps_multilayer_extension syntax that is conditional on a pps_extension_type_flag[1] flag.
17. The method of claim 15 , wherein the at least one of the phase shifts is signaled conditional on a scaled_reference_phase_present_flag flag.
18. The method of claim 15 , wherein the at least one of the phase shifts specifies a horizontal component of the phase shift used in the resampling process.
19. The method of claim 15 , wherein the at least one of the phase shifts specifies a vertical component of the phase shift used in the resampling process.
20. The method of claim 1 , further comprising:
determining if a pps_extension_type_flag[1] is set indicating presence of the pps_multilayer_extension syntax structure;
parsing the pps_multilayer_extension syntax structure if the pps_extension_type_flag[1] is set; and
determining if a scaled_reference_offset_present_flag_flag is set to determine whether the scaled offsets and phase shifts are present in the one or more syntax structures at the picture level.