Adaptive sampling filter process for scalable video coding
View Patent ↗A sampling filter process for scalable video coding provides correction for phase shift occurring during downsampling. The process uses video data obtained from an encoder or decoder process of a base layer (BL) in a multi-layer system using adaptive phase shifting based on downsampling to improve quality. Examples of a multi-layers are MPEG-4 Advanced Video Coding (AVC) and High Efficiency Video Coding (HEVC). The re-sampled BL data can be used in higher layers in a scalable video coding system. For example, the re-sampled or upsampled data can be used as a basis for prediction of the higher resolution video data.
1. A system for scalable video coding comprising:
a first coding layer for coding video with a base resolution;
a second coding layer for coding video with an enhanced resolution having a higher resolution than the base resolution;
an upsampling unit receiving sampling signals from the first coding layer and providing an output signal to the second coding layer after an upsampling process, wherein the upsampling unit output signal enables more efficient coding in the second coding layer,
wherein the first coding layer is downsampled from the second coding layer, and wherein a global phase offset generated in the downsampling is calculated during the upsampling to provide the output signal from the upsampling unit
wherein phase shift q_c is used during downsampling,
wherein phase shift p_c is used during upsampling,
wherein r is a factor used in downsampling from the enhanced resolution to the base resolution and in upsampling from the base resolution to the enhanced resolution,
and
wherein the phase shift q_c and the phase shift p_c provide a vertical chroma phase offset, respectively in the downsampling and upsampling, with the phase shift q_c=(r−1)/4 and
wherein the downsampling by the factor of r and the upsampling by the factor of r, the phase shift p_c=−q_c/r=(1−r)/(4r) is calculated as the global phase offset.
2. The system for scalable video coding of claim 1 , wherein the global phase offset used in upsampling is computed by a decoder in the second coding layer.