Perceptual image and video coding
Methods and devices for perceptual image and video coding. A method for reconstructing a quantization parameter for a current block includes predicting the quantization parameter, wherein predicting the quantization parameter is based upon a previous quantization parameter used for a neighboring block in the image, an estimated AC energy of the neighboring block, and an estimated AC energy of the current block; decoding from the bitstream a quantization parameter residual; and deriving the quantization parameter from the predicted quantization parameter and the quantization parameter residual. The method may include reconstructing the pixels of the current block, including dequantizing decoded quantized transform domain coefficients based on the quantization parameter.
1. A method of decoding an image from a bitstream of encoded data using a decoder, the image being partitioned into blocks, the method comprising:
for a current block of the image,
determining a predicted value of a quantization parameter to be used in decoding the current block, wherein the predicted value is based upon
a previous quantization parameter used for a neighboring block in the image,
an estimated AC energy of the neighboring block, and
an estimated AC energy of the current block;
decoding from the bitstream a quantization parameter residual and deriving the quantization parameter from the predicted value and the quantization parameter residual; and
reconstructing the pixels of the block, including dequantizing decoded quantized transform domain coefficients based on the quantization parameter.
2. The method claimed in claim 1 , wherein the predicted value is further based upon a second previous quantization parameter used for another neighboring block in the image.
3. The method claimed in claim 2 , wherein the neighboring block and the another neighboring block comprise the block to the left of the current block in the image and the block above the current block in the image.
4. The method claimed in claim 1 , wherein the predicted value is further based upon a second previous quantization parameter used for a previous quantization group in decoding order or obtained from header information for the image.
5. The method claimed in claim 1 , wherein the quantization parameter comprises one of a plurality of defined QP values, and wherein dequantizing decoded quantized transform domain coefficients based on the quantization parameter identifying a quantization step size corresponding to that QP value and using that quantization step size in the dequantization.
6. The method claimed in claim 1 , wherein the estimated AC energy of the neighboring block comprises the AC energy of a prediction of the neighboring block, and wherein the estimated AC energy of the current block comprises the AC energy of a prediction of the current block.
7. The method claimed in claim 1 , wherein the estimated AC energy of the neighboring block comprises the AC energy of a reconstruction of the neighboring block, and wherein the estimated AC energy of the current block is estimated based upon:
the AC energy of a prediction of the current block, and
a difference between the AC energy of the reconstruction of the neighboring block and the AC energy of a prediction of the neighboring block.
8. The method claimed in claim 1 , wherein each block comprises one of a coding unit, a group of coding units, and a quantization group containing multiple coding units.
9. A decoder for decoding an image from a bitstream of encoded data, the image being partitioned into blocks, the decoder comprising:
a processor;
a memory; and
a decoding application stored in memory and containing instructions executable by the processor to
for a current block of the image,
determine a predicted value of a quantization parameter to be used in decoding the current block, wherein the predicted value is based upon
a previous quantization parameter used for a neighboring block in the image,
an estimated AC energy of the neighboring block, and
an estimated AC energy of the current block,
decode from the bitstream a quantization parameter residual and derive the quantization parameter from the predicted value and the quantization parameter residual, and
reconstruct the pixels of the block by dequantizing decoded quantized transform domain coefficients based on the quantization parameter.
10. The decoder claimed in claim 9 , wherein the predicted value is further based upon a second previous quantization parameter used for another neighboring block in the image.
11. The decoder claimed in claim 10 , wherein the neighboring block and the another neighboring block comprise the block to the left of the current block in the image and the block above the current block in the image.
12. The decoder claimed in claim 9 , wherein the predicted value is further based upon a second previous quantization parameter used for a previous quantization group in decoding order or obtained from header information for the image.
13. The decoder claimed in claim 9 , wherein the quantization parameter comprises one of a plurality of defined QP values, and wherein the processor is to dequantize decoded quantized transform domain coefficients based on the quantization parameter identifying a quantization step size corresponding to that QP value and using that quantization step size in the dequantization.
14. The decoder claimed in claim 9 , wherein the estimated AC energy of the neighboring block comprises the AC energy of a prediction of the neighboring block, and wherein the estimated AC energy of the current block comprises the AC energy of a prediction of the current block.
15. The decoder claimed in claim 9 , wherein the estimated AC energy of the neighboring block comprises the AC energy of a reconstruction of the neighboring block, and wherein the estimated AC energy of the current block is estimated based upon:
the AC energy of a prediction of the current block, and
a difference between the AC energy of the reconstruction of the neighboring block and the AC energy of a prediction of the neighboring block.
16. The decoder claimed in claim 9 , wherein each block comprises one of a coding unit, a group of coding units, and a quantization group containing multiple coding units.
17. A non-transitory processor-readable medium storing processor-executable instructions for decoding an image from a bitstream of encoded data using a decoder, the image being partitioned into blocks, wherein the processor-executable instructions comprise:
for a current block of the image,
instructions to determine a predicted value of a quantization parameter to be used in decoding the current block, wherein the predicted value is based upon
a previous quantization parameter used for a neighboring block in the image,
an estimated AC energy of the neighboring block, and
an estimated AC energy of the current block;
instructions to decode from the bitstream a quantization parameter residual and derive the quantization parameter from the predicted value and the quantization parameter residual; and
instructions to reconstruct the pixels of the block, including dequantizing decoded quantized transform domain coefficients based on the quantization parameter.
18. The non-transitory processor-readable medium claimed in claim 17 , wherein the predicted value is further based upon a second previous quantization parameter used for another neighboring block in the image.
19. The non-transitory processor-readable medium claimed in claim 18 , wherein the neighboring block and the another neighboring block comprise the block to the left of the current block in the image and the block above the current block in the image.
20. The non-transitory processor-readable medium claimed in claim 17 , wherein the estimated AC energy of the neighboring block comprises the AC energy of a prediction of the neighboring block, and wherein the estimated AC energy of the current block comprises the AC energy of a prediction of the current block.