Method for encoding and/or decoding images on macroblock level using intra-prediction
Conventional intra-prediction uses pixels from left and upper neighbour blocks to predict a macroblock (MB). Thus, the MBs must be sequentially processed, since reconstructed left and upper MBs must be available for prediction. In an improved method for encoding Intra predicted MBs, a MB is encoded in two steps: first, a first portion of the MB is encoded independently, without references outside the MB. Pixels of the first portion can be Intra predicted using DC mode. Then, the first portion is reconstructed. The remaining pixels of the MB, being a second portion, are intra predicted from the reconstructed pixels of the first portion and then reconstructed. The first portion comprises at least one column or one row of pixels of the MB. The encoding is applied to at least two Intra predicted MBs per slice, or per picture if no slices are used.
1. A non-transitory computer readable medium with instructions stored therein which, upon execution, instruct at least one processor to decode a block of an image using intra prediction, wherein the decoding comprises:
decoding a syntax element specifying that the block is encoded according to an intra coding mode, the intra coding mode excluding a DC mode;
determining two portions in the block, wherein a first portion comprises independent pixels of the block, and a second portion comprises remaining pixels of the block;
intra-predicting the independent pixels of the first portion based on an average value relative to a bit depth of pixels of the block;
decoding the first portion using the intra-predicted pixels of the first portion;
intra-predicting, using the intra coding mode, one or more pixels of the second portion using decoded pixels of the first portion or one or more previously decoded pixels of the second portion; and
decoding the second portion using the one or more intra-predicted pixels of the second portion, wherein decoded pixels of the first portion and decoded pixels of the second portion are part of a decoded block.
2. The non-transitory computer readable medium of claim 1 , wherein the first portion comprises at least half the pixels of one column and half the pixels of one row.
3. The non-transitory computer readable medium of claim 1 , wherein the intra coding mode depends on block division into two portions.
4. The non-transitory computer readable medium of claim 1 , wherein a size of a block encoded according to the intra coding mode is larger than 16×16.
5. The non-transitory computer readable medium of claim 1 , wherein the image comprises at least one slice, and wherein at least two intra-coded blocks per slice are decoded simultaneously.
6. The non-transitory computer readable medium of claim 1 , wherein the intra-predicted pixels of the first portion are based on a power of two whose exponent is equal to the bit depth of pixels of the block minus one.
7. A non-transitory computer readable medium with instructions stored therein which, upon execution, instruct at least one processor to encode a block of an image using intra prediction, wherein the encoding comprises:
dividing the block into two portions, wherein a first portion comprises independent pixels of the block, and a second portion comprises remaining pixels of the block;
intra-predicting the independent pixels of the first portion based on an average value relative to a bit depth of pixels of the block;
encoding the first portion using the intra-predicted pixels of the first portion;
reconstructing encoded pixels of the first portion;
intra-predicting, using an intra coding mode that excludes a DC mode, one or more of the remaining pixels of the second portion using reconstructed pixels of the first portion or one or more previously reconstructed pixels of the second portion;
encoding the second portion using the one or more intra-predicted pixels of the second portion wherein encoded pixels of the first portion and encoded pixels of the second portion are part of an encoded block, the encoded block being encoded by the intra coding mode;
reconstructing the one or more previously encoded pixels of the second portion; and
encoding a syntax element specifying that the block is encoded according to the intra coding mode.
8. The non-transitory computer readable medium of claim 7 , wherein the first portion comprises at least half the pixels of one column and half the pixels of one row.
9. The non-transitory computer readable medium of claim 7 , wherein the intra coding mode depends on block division into two portions.
10. The non-transitory computer readable medium of claim 7 , wherein a size of a block encoded according to the intra prediction mode is larger than 16×16.
11. The non-transitory computer readable medium of claim 7 , wherein the image comprises at least one slice, and wherein at least two intra-coded blocks per slice are encoded simultaneously.
12. The non-transitory computer readable medium of claim 7 , wherein the intra-predicted pixels of the first portion are based on a power of two whose exponent is equal to the bit depth of pixels of the block minus one.
13. A non-transitory computer readable storage media having video data encoded thereupon, comprising:
an intra-coded block including (i) a first intra-coded portion for a first portion of the block that includes independent pixels and (ii) a second intra-coded portion for a second portion of the block that includes remaining pixels; and
an indicator of an intra-coding mode associated with the intra-coded block, wherein the intra coding mode excludes a DC mode;
wherein the first intra-coded portion is intra-coded based on an average value of a bit depth of pixels in the block;
wherein at least a part of the second intra-coded portion is intra-coded using the intra-coding mode based on reconstructed pixels of the intra-coded first portion or one or more previously reconstructed pixels of the second portion of the block.
14. A method comprising transmitting video data, said transmitted video data comprising:
an intra-coded block including (i) a first intra-coded portion for a first portion of the block that includes independent pixels and (ii) a second intra-coded portion for a second portion of the block that includes remaining pixels; and
an indicator of an intra-coding mode associated with the intra-coded block, wherein the intra coding mode excludes a DC mode;
wherein the first intra-coded portion is intra-coded based on an average value of a bit depth of pixels in the block;
wherein at least a part of the second intra-coded portion is intra-coded using the intra-coding mode based on reconstructed pixels of the intra-coded first portion or one or more previously reconstructed pixels of the second portion of the block.
15. An apparatus comprising at least a memory and one or more processors, wherein the one or more processors are configured to transmit video data, said transmitted video data comprising:
an intra-coded block including (i) a first intra-coded portion for a first portion of the block that includes independent pixels and (ii) a second intra-coded portion for a second portion of the block that includes remaining pixels; and
an indicator of an intra-coding mode associated with the intra-coded block, wherein the intra coding mode excludes a DC mode;
wherein the first intra-coded portion is intra-coded based on an average value of a bit depth of pixels in the block;
wherein at least a part of the second intra-coded portion is intra-coded using the intra-coding mode based on reconstructed pixels of the intra-coded first portion or one or more previously reconstructed pixels of the second portion of the block.
16. A method comprising receiving video data, said video data comprising:
an intra-coded block including (i) a first intra-coded portion for a first portion of the block that includes independent pixels and (ii) a second intra-coded portion for a second portion of the block that includes remaining pixels; and
an indicator of an intra-coding mode associated with the intra-coded block, wherein the intra coding mode excludes a DC mode;
wherein the first intra-coded portion is intra-coded based on an average value of a bit depth of pixels in the block;
wherein at least a part of the second intra-coded portion is intra-coded using the intra-coding mode based on reconstructed pixels of the intra-coded first portion or one or more previously reconstructed pixels of the second portion of the block.
17. An apparatus comprising at least a memory and one or more processors, wherein the one or more processors are configured to receive video data, said video data comprising:
an intra-coded block including (i) a first intra-coded portion for a first portion of the block that includes independent pixels and (ii) a second intra-coded portion for a second portion of the block that includes remaining pixels; and
an indicator of an intra-coding mode associated with the intra-coded block, wherein the intra coding mode excludes a DC mode;
wherein the first intra-coded portion is intra-coded based on an average value of a bit depth of pixels in the block;
wherein at least a part of the second intra-coded portion is intra-coded using the intra-coding mode based on reconstructed pixels of the intra-coded first portion or one or more previously reconstructed pixels of the second portion of the block.