Re-sampling with phase offset adjustment for luma and chroma to select filters in scalable video coding
View Patent ↗A sampling filter process 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 using adaptive phase shifting to improve quality in Scalable High efficiency Video Coding (SHVC). In order to compensate for phase offsets introduced by downsampling an appropriate phase offset adjustment is made for upsampling in SHVC with an appropriate offset included for proper luma/chroma color space positions. In one approach the luma/chroma phase offset is specified and a filter is selected to apply the appropriate phase change.
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 upsampling unit comprises:
a first module formed by code executable in a processor for selecting input samples of the video signal in the first coding layer;
a second module formed by code executable in a processor providing selection of a plurality of filters for processing the selected input samples;
and a third module including the plurality of filters, the third module formed by code executable in a processor for filtering the selected input samples with the selected filters, the third module providing the output signal from the upsampling unit, wherein the first coding layer is downsampled from the second coding layer, wherein a first phase offset is generated to select one of the filters used in the upsampling process to provide the output signal from the upsampling unit, and wherein at least one of luma phase offset and chroma phase offset in downsampling is used to determine the first phase offset to select the one of the filters in the upsampling process,
wherein the luma phase offset and the chroma phase offset are specified for both row and column filtering, and
wherein a sample location xRef16 and yRef16 for the first module is determined with the luma phase offset for row denoted, luma phase offset [0], the luma phase offset for column denoted, luma phase offset[1], the chroma phase offset for row denoted, chroma phase offset[0], the chroma phase offset for column denoted, chroma phase offset[1],
all considered using the following equations for luma offset:
x Ref16=( xP *PicWRL*16+Scaled W/ 2)/Scaled W +luma phase offset[0]
y Ref16=( yP *PicHRL*16+Scaled H/ 2)/Scaled H +luma phase offset[1]
and the following equations for the chroma offset:
x Ref16=( xP *PicWRL*16+Scaled W/ 2)/Scaled W +chroma phase offset[0]
y Ref16=( yP *PicHRL*16+Scaled H/ 2)/Scaled H +chroma phase offset[1]
wherein xP and yP are a sample location relative to a top left sample, PicWRL is the picture width reference layer, PicHRL is the picture height reference layer, and ScaledW and ScaledH are the scalable width and height in the second coding layer.
2. The system of claim 1 , wherein both the luma phase offset and the chroma phase offset are determined and included in the first phase offset to select the one of the filters in the upsampling process.
3. The system of claim 1 , wherein it is signaled from an encoder to a decoder using a flag in the second coding layer whether the first coding layer data is deblocked data.
4. The system of claim 1 , wherein when data has been deblocked it is signaled from an encoder to a decoder using a flag in the second coding layer whether the first coding layer data has been processed with SAO.
5. The system of claim 1 , wherein the selection of a filter from the plurality of filters third module is controlled by selection from the second module based on the first phase offset determination.
6. A method for scalable video coding comprising: receiving sampling signals from the first coding layer and providing an output signal to a second coding layer that codes video with an enhanced resolution having a higher resolution than the base resolution;
selecting input samples of the video signal in the first coding layer for coding video with a base resolution; selecting a filter from a plurality of filters for processing the selected input samples for an upsampling process; and
filtering the selected input samples with the selected filter, wherein a first phase offset is generated to select one the filters used to provide the output in the upsampling process, and wherein at least one of luma phase offset and chroma phase offset is determined and included in the first phase offset to select the one of the filters for the upsampling process,
wherein both the luma phase offset and the chroma hale offset are determined and included in the first phase offset to select the filters for the upsampling process,
wherein the luma phase offset and the chroma phase offset are specified for both row and column filtering,
a sample location xRef16 and yRef16 is determined with the luma phase offset for row denoted, luma phase offset[0], the luma phase offset for column denoted, luma phase offset[1], the chroma phase offset for row denoted, chroma phase offset[0], the chroma phase offset for column denoted, chroma phase offset[1], all considered using the following equations for luma offset:
x Ref16=( xP *PicWRL*16+Scaled W/ 2)/Scaled W +luma phase offset[0]
y Ref16=( yP *PicHRL*16+Scaled H/ 2)/Scaled H +luma phase offset[1]
and the following equations for the chroma offset:
x Ref16=( xP *PicWRL*16+Scaled W/ 2)/Scaled W +chroma phase offset[0]
y Ref16=( yP *PicHRL*16+Scaled H/ 2)/Scaled H +chroma phase offset[1]
wherein xP and yP are a sample location relative to a top left sample, PicWRL is the picture width reference layer, PicHRL is the picture height reference layer, and ScaledW and ScaledH are the scalable width and height in the second coding layer.
7. The method of claim 6 , wherein both the luma phase offset and the chroma phase offset are determined and included in the first phase offset to select the filters for the upsampling process.
8. The method of claim 6 , wherein it is signaled from an encoder to a decoder using a flag in the second coding layer whether the first coding layer data is deblocked data.
9. The method of claim 6 , wherein when data has been deblocked it is signaled from an encoder to a decoder using a flag in the second coding layer whether the first coding layer data has been processed with SAO.
10. The method of claim 6 , wherein the selection of a filter from the plurality of filters third module is controlled by selection from the second module based on the first phase offset determination.