Quantization parameter signaling
AssigneeDolby Laboratories Licensing Corporation
InventorsFangjun Pu, Taoran Lu, Peng Yin, Sean Thomas McCarthy
Life of this patent
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Abstract
A quantization parameter signaling mechanism for both SDR and HDR content in video coding is described using two approaches. The first approach is to send the user-defined QpC table directly in high level syntax. This leads to more flexible and efficient QP control for future codec development and video content coding. The second approach is to signal luma and chroma QPs independently. This approach eliminates the need for QpC tables and removes the dependency of chroma quantization parameter on luma QP.
Claims7
An apparatus to reconstruct coded data, the apparatus comprising:
- means for receiving a coded bitstream comprising one or more coded pictures, wherein each picture comprises a luminance component, a first chroma component, and a second chroma component;
- means for extracting syntax parameters from the coded bitstream to determine a chroma quantization parameter (QP) table, wherein the chroma QP table maps input luminance QP values to corresponding chroma QP values;
- and
- means for decoding the one or more coded pictures based on the chroma QP table, wherein the syntax parameters comprise a start luminance QP value and one or more offset parameters to determine a mapping of the luminance QP values to corresponding chroma QP values using a piece-wise linear representation, wherein for luminance quantization values qP[i] for i larger than an end index value, corresponding chroma quantization values (Qpc[i]) are determined as Qpc[i]=qP[i]-offset, where offset denotes a fixed value.
A apparatus to encode a sequence of video pictures to generate a coded video bitstream, the apparatus comprising:
- means for receiving a sequence of pictures wherein each picture comprises a luminance component, a first chroma component, and a second chroma component;
- means for encoding the sequence of video pictures using luminance quantization parameters (QP) values and chroma QP values to generate a coded video bitstream;
- and
- means for encoding signal parameters in the coded video bitstream for a decoder to determine a chroma QP table, wherein the chroma QP table maps input luminance QP values to corresponding chroma QP values, wherein the signal parameters comprise a start luminance QP value and one or more offset parameters to determine a mapping of the luminance QP values to the corresponding chroma QP values using a piece-wise linear representation, wherein for luminance quantization values qP[i] for i larger than an end index value, corresponding chroma quantization values (Qpc[i]) are determined as Qpc[i]=qP[i]-offset, where offset denotes a fixed value.
A method for transmitting a bitstream which is generated by a video encoding apparatus and used to reconstruct a video, wherein the method comprises:
- transmitting the bitstream, wherein generating the bitstream comprises:
- receiving a sequence of pictures wherein each picture comprises a luminance component, a first chroma component, and a second chroma component;
- encoding the sequence of video pictures using luminance quantization parameters (QP) values and chroma QP values to generate a coded video bitstream;
- and
- encoding signal parameters in the coded video bitstream for a decoder to determine a chroma QP table, wherein the chroma QP table maps input luminance QP values to corresponding chroma QP values, wherein the signal parameters comprise a start luminance QP value and one or more offset parameters to determine a mapping of the luminance QP values to the corresponding chroma QP values using a piece-wise linear representation, wherein for luminance quantization values qP[i] for i larger than an end index value, corresponding chroma quantization values (Qpc[i]) are determined as Qpc[i]=qP[i]-offset, where offset denotes a fixed value.
Dependencies are inferred from the claim text.