BACKGROUND

Technical Field

The present invention relates to the process of using a two layer Scalable Video Coding (SVC) scheme for encoding and decoding of video sequences derived from the same source with differences in resolution. More specifically, it relates to arranging, prediction and reconstruction of video data obtained from an encoder or decoder process during scalable coding. Examples of scalable encoder or decoder processes include MPEG-4 Advanced Video Coding (AVC) and High Efficiency Video Coding (HEVC) that can be labeled Scalable HEVC (SHVC).

Related Art

An example of a scalable video coding system using two layers where color tone mapping can be applied is shown inFIG. 1. In the system ofFIG. 1, one of the two layers is the Base Layer (BL) where a BL video is encoded in an Encoder E0, labeled100, and decoded in a decoder D0, labeled102, to produce a base layer video output BL out. The BL video is typically at a lower quality than the Enhancement Layer (EL) that receives an input y from the Full Resolution (FR) layer. The EL includes an encoder E1, labeled104, for encoding the FR video, as well as a decoder D1, labeled106. In encoding in encoder E1104of the full resolution video, cross-layer (CL) information from the BL encoder100is used to produce enhancement layer (EL) information. The corresponding EL bitstream of the full resolution layer is then decoded in decoder D1106using the CL information from decoder D0102of the BL to output full resolution video, FR out. By using CL information in a scalable video coding system, the encoded information can be transmitted more efficiently in the EL than if the FR was encoded independently without the CL information. An example of SVC coding that can use two layers shown inFIG. 1includes video coding using AVC and HEVC.

In spatial scalability, the BL is typically at a lower spatial resolution than Full Resolution (FR), as illustrated inFIG. 1with a downsampling conversion process is applied from FR to BL.FIG. 1shows block108with a down-arrow r illustrating a resolution reduction from the FR to the BL to illustrate that the BL can be created by a downsampling of the FR layer data. Overall, the down arrow of block108illustrates that for scalability, the base layer BL is typically at a lower spatial resolution than the full resolution FR layer. It is worth noting that the multilayer methods described apply when there are more than two layers.

The CL information from the BL later can be used after upsampling to enhance the coding of the FR video in the EL. In the system ofFIG. 1in combination with an upsampler ofFIG. 2, the CL information includes pixel information derived from the encoding and decoding process of the BL. Because the BL pictures are at a different spatial resolution than the FR pictures, a BL picture needs to be upsampled (or re-sampled) back to the FR picture resolution in order to generate a suitable prediction for the FR picture.

SUMMARY

Embodiments of the present invention provide systems for SVC that account for color gamut conversion between layers as well as spatial resolution conversion in some embodiments. The process provides for re-sampling using video color data obtained from an encoder or decoder process of a base layer (BL) in a multi-layer system to enable improved encoding and decoding in an enhancement layer (EL) or higher layers taking into account color conversion between layers. For example, with the reconstructed data, video data expressed in a lower resolution in one color gamut space can be used to predict a higher resolution video in another color gamut space and can also account for a different bit-depth.

In one further embodiment, a different color mapping is applied to different regions of a video frame. The mapping to different frame regions can be done by at least one of the following procedures: (a) signaling linear or non-linear 3DLUT color mapping parameters with an adaptive quad-tree structure; (b) signaling mapping parameters in the slice or tile headers to create the same spatial freedom for correcting the color tones; (c) signaling to reuse collocated partitioning and color mapping parameters from previous frames; and (d) using the adaptive quad-tree partitioning to adaptively signal filter parameters in the case that spatial scalability is also applied.

In a further embodiment, both color tone mapping from a base to a target color gamut and spatial scaling are separately applied in an order where one is applied first and then the other. In one embodiment when the color gamut scaling is applied for a tone mapping function in an encoder side, the tone mapping function occurs after spatial scaling. Then the reverse order of spatial scaling applied first and then tone mapping applied occurs at a decoder side.

In a further embodiment, the tone mapping is applied as a function mapping from a vector of three color values in one color gamut space to a corresponding vector of three color values in a different gamut space. The mapping can also map to values in the same color space. The mapping at the encoder is then applied on a three-color-component grid that is different than a grid a Base Layer (BL) is on. In this embodiment, a relative location of luma and chroma samples in vertical and horizontal dimensions are signaled to a decoder to enable the decoder to adjust the sample locations to reverse the one used for the tone mapping in a forward direction.

