Rolling intra prediction for image and video coding
Methods and devices for image and video coding using rolling intra prediction. The encoder selects a mode for a current block, the current block having a plurality of neighboring reference samples from an adjacent block, wherein the mode is associated with a prediction function. A predicted block of predicted pixels is constructed by initially determining at least some of the predicted pixels based on the prediction function with one or more of the neighboring reference samples as inputs to the prediction function, and by determining at least some other of the predicted pixels based on the prediction function with the at least some of the predicted pixels as inputs. The process proceeds to build the predicted block in a traversing order using predicted pixels of the same predicted block as inputs to the prediction function for determining other predicted pixels of the predicted block. The decoder performs the same prediction process.
1. A method of decoding an image in a video or image decoder from a bitstream, the method comprising:
decoding a mode from the bitstream for a current block, the current block having a plurality of neighboring reference samples from an adjacent block, wherein the mode is associated with a prediction function;
selecting a template from among a plurality of templates based on a traversing order, wherein the template specifies relative locations of three or more nearby pixels to be used as inputs to the prediction function for a particular pixel;
constructing a predicted block of predicted pixels for the current block, wherein constructing includes selecting the traversing order according to the mode decoded from the bitstream and, in the traversing order,
determining at least some of the predicted pixels based on the prediction function and the template with one or more of the neighboring reference samples as inputs to the prediction function, and
determining at least some other of the predicted pixels based on the prediction function and the template with the at least some of the predicted pixels as inputs;
decoding residual data to create a reconstructed residual block for the current block; and
reconstructing the current block as the sum of the predicted block and the reconstructed residual block.
2. The method claimed in claim 1 , wherein the determining at least some other of the predicted pixels is based on the prediction function excluding any neighboring reference samples as inputs.
3. The method claimed in claim 1 , wherein the neighboring reference samples comprise previously-reconstructed pixels neighboring the current block.
4. The method claimed in claim 1 , wherein the prediction function comprises a linear function of two or more pixels near the particular pixel.
5. The method claimed in claim 1 , wherein the traversing order is a horizontal raster scan order.
6. The method claimed in claim 1 , wherein constructing comprises defining a work block in memory, populating a first column and a first row of work block samples of the work block with the neighboring reference samples, and determining, in a traversing order, additional work block samples of the work block based on the prediction function and the template, and wherein a portion of the additional work block samples comprise the predicted pixels.
7. The method claimed in claim 6 , wherein constructing further comprises determining a work block size based on a size of the predicted block and based on the mode.
8. A decoder for decoding an image from a bitstream, the image being partitioned into blocks and having a current block, the decoder comprising:
a processor;
memory storing a plurality of neighboring reference samples from an adjacent block; and
a decoding application containing instructions executable by the processor that, when executed, cause the processor to
decode a mode from the bitstream for the current block, wherein the mode is associated with a prediction function,
select a template from among a plurality of templates based on traversing order, wherein the template specifies relative locations of three or more nearby pixels to be used as inputs to the prediction function for a particular pixel;
construct a predicted block of predicted pixels for the current block, wherein constructing includes selecting the traversing order according to the mode decoded from the bitstream and, in the traversing order,
determining at least some of the predicted pixels based on the prediction function and the template with one or more of the neighboring reference samples as inputs to the prediction function, and
determining at least some other of the predicted pixels based on the prediction function and the template with the at least some of the predicted pixels as inputs, and
decode residual data to create a reconstructed residual block for the current block; and
reconstruct the current block as the sum of the predicted block and the reconstructed residual block.
9. A non-transitory processor-readable medium storing processor-executable instructions for decoding an image in a video or image decoder from a bitstream, wherein the processor-executable instructions, when executed by a processor in the video or image decoder, cause the processor to perform the method of:
decoding a mode from the bitstream for a current block, the current block having a plurality of neighboring reference samples from an adjacent block, wherein the mode is associated with a prediction function;
selecting a template from among a plurality of templates based on a traversing order, wherein the template specifies relative locations of three or more nearby pixels to be used as inputs to the prediction function for a particular pixel;
constructing a predicted block of predicted pixels for the current block, wherein constructing includes selecting the traversing order according to the mode decoded from the bitstream and, in the traversing order,
determining at least some of the predicted pixels based on the prediction function and the template with one or more of the neighboring reference samples as inputs to the prediction function, and
determining at least some other of the predicted pixels based on the prediction function and the template with the at least some of the predicted pixels as inputs;
decoding residual data to create a reconstructed residual block for the current block; and
reconstructing the current block as the sum of the predicted block and the reconstructed residual block.
10. A method of encoding an image in a video or image encoder to produce a bitstream, the method comprising:
selecting a mode for a current block, the current block having a plurality of neighboring reference samples from an adjacent block, wherein the mode is associated with a prediction function;
selecting a template from among a plurality of templates based on a traversing order, wherein the template specifies relative locations of three or more nearby pixels to be used as inputs to the prediction function for a particular pixel;
constructing a predicted block of predicted pixels for the current block, wherein constructing includes selecting the traversing order according to the mode selected for the current block and, in the traversing order,
determining at least some of the predicted pixels based on the prediction function and the template with one or more of the neighboring reference samples as inputs to the prediction function, and
determining at least some other of the predicted pixels based on the prediction function and the template with the at least some of the predicted pixels as inputs;
determining residual data as the difference between the current block and the predicted block; and
encoding the residual data and the selected mode for output as a portion of the bitstream.
11. The method claimed in claim 10 , wherein the determining at least some other of the predicted pixels is based on the prediction function excluding any neighboring reference samples as inputs.
12. The method claimed in claim 10 , wherein the neighboring reference samples comprise previously-reconstructed pixels neighboring the current block.
13. The method claimed in claim 10 , wherein the prediction function comprises a linear function of two or more pixels near the particular pixel.
14. The method claimed in claim 10 , wherein the traversing order is a horizontal raster scan order.
15. The method claimed in claim 10 , wherein constructing comprises defining a work block in memory, populating a first column and a first row of work block samples of the work block with the neighboring reference samples, and determining, in a traversing order, additional work block samples of the work block based on the prediction function and the template, and wherein a portion of the additional work block samples comprise the predicted pixels.
16. The method claimed in claim 15 , wherein constructing further comprises determining a work block size based on a size of the predicted block and based on the mode.
17. An encoder for encoding an image to produce a bitstream of encoded data, the image being partitioned into blocks and having a current block, the encoder comprising:
a processor;
memory storing a plurality of neighboring reference samples from an adjacent block; and
an encoding application containing instructions executable by the processor that, when executed, cause the processor to
select a mode for the current block, wherein the mode is associated with a prediction function,
select a template from among a plurality of templates based on a traversing order, wherein the template specifies relative locations of three or more nearby pixels to be used as inputs to the prediction function for a particular pixel;
construct a predicted block of predicted pixels for the current block, wherein to construct includes to select the traversing order according to the mode selected for the current block and, in the traversing order,
to determine at least some of the predicted pixels based on the prediction function and the template with one or more of the neighboring reference samples as inputs to the prediction function, and
to determine at least some other of the predicted pixels based on the prediction function and the template with the at least some of the predicted pixels as inputs, and
determine residual data as the difference between the current block and the predicted block; and
encode the residual data and the selected mode for output as a portion of the bitstream.
18. A non-transitory processor-readable medium storing processor-executable instructions for encoding an image in a video or image encoder to produce a bitstream, wherein the processor-executable instructions, when executed by a processor in the video or image encoder, cause the processor to perform the method of:
selecting a mode for a current block, the current block having a plurality of neighboring reference samples from an adjacent block, wherein the mode is associated with a prediction function;
selecting a template from among a plurality of templates based on a traversing order, wherein the template specifies relative locations of three or more nearby pixels to be used as inputs to the prediction function for a particular pixel;
constructing a predicted block of predicted pixels for the current block, wherein constructing includes selecting the traversing order according to the mode selected for the current block and, in the traversing order,
determining at least some of the predicted pixels based on the prediction function and the template with one or more of the neighboring reference samples as inputs to the prediction function, and
determining at least some other of the predicted pixels based on the prediction function and the template with the at least some of the predicted pixels as inputs;
determining residual data as the difference between the current block and the predicted block; and
encoding the residual data and the selected mode for output as a portion of the bitstream.