Method for coding and an apparatus based on a DC prediction value

1. A method comprising:

receiving a block of pixels;

determining a set of potential reference samples for the block of pixels, wherein the set of potential reference samples for the block of pixels comprises at least a part of the pixels of an encoded neighboring block which is adjacent to the block of pixels;

selecting a subset of the set of potential reference samples to be used as reference samples for the block of pixels, wherein the selected subset of reference samples comprises sets of n consecutive reference samples with m reference samples between the sets wherein variables n and m are positive integers; and

using the selected subset of reference samples to determine a DC prediction value for the block of pixels.

2. A method according to claim 1 further comprising determining a prediction error for a pixel in the block of pixels on the basis of the DC prediction value and the value of the pixel in the block of pixels.

3. A method according to claim 1 , wherein the received block of pixels differs from a square, wherein the method comprises selecting all samples on a boundary having smaller number of potential reference samples than another boundary, and selecting the same number of samples on the other boundary.

4. A method comprising:

receiving an encoded block of pixels;

determining a set of potential reference samples for the block of pixels;

selecting a subset of the set of potential reference samples to be used as reference samples for the block of pixels wherein the set of potential reference samples for the block of pixels comprises at least a part of the pixels of an encoded neighboring block which is adjacent to the block of pixels;

determining reference samples for the encoded block of pixels, wherein the selected subset of reference samples comprises sets of n consecutive reference samples with m reference samples between the sets wherein variables n and m are positive integers;

using the determined reference samples to define a DC prediction value for the block of pixels;

receiving a prediction error for a pixel of the encoded block of pixels; and

reconstructing the pixel value on the basis of the DC prediction value and the prediction error.

5. A method according to claim 4 , wherein the received block of pixels differs from a square, wherein the method comprises selecting all samples on a boundary having smaller number of potential reference samples than another boundary, and selecting the same number of samples on the other boundary.

6. An apparatus comprising a processor and a memory including computer program code, the memory and the computer program code configured to, with the processor, cause the apparatus to:

receive a block of pixels;

determine a set of potential reference samples for the block of pixels, wherein the set of potential reference samples for the block of pixels comprises at least a part of the pixels of an encoded neighboring block which is adjacent to the block of pixels; and

select a subset of the set of potential reference samples to be used as reference samples for the block of pixels, wherein the selected subset of reference samples comprises sets of n consecutive reference samples with m reference samples between the sets wherein variables n and m are positive integers;

use the selected subset of reference samples to determine a DC prediction value for the block of pixels.

7. An apparatus according to claim 6 , the memory and the computer program code further configured to, with the processor, cause the apparatus to determine a prediction error for a pixel in the block of pixels on the basis of the DC prediction value and the value of the pixel in the block of pixels.

8. An apparatus comprising a processor and a memory including computer program code, the memory and the computer program code configured to, with the processor, cause the apparatus to:

receive an encoded block of pixels;

determine a set of potential reference samples for the block of pixels, wherein the set of potential reference samples for the block of pixels comprises at least a part of the pixels of an encoded neighboring block which is adjacent to the block of pixels;

select a subset of the set of potential reference samples to be used as reference samples for the block of pixels, wherein the selected subset of reference samples comprises sets of n consecutive reference samples with m reference samples between the sets wherein variables n and m are positive integers;

determine reference samples for the encoded block of pixels;

use the determined reference samples to define a DC prediction value for the block of pixels;

receive a prediction error for a pixel of the encoded block of pixels; and

reconstruct the pixel value on the basis of the DC prediction value and the prediction error.

9. A non-transitory storage medium having stored thereon a computer program code, said program codes comprising instructions for use by an encoder, said program code comprising instructions for:

receiving a block of pixels;

determining a set of potential reference samples for the block of pixels, wherein the set of potential reference samples for the block of pixels comprises at least a part of the pixels of an encoded neighboring block which is adjacent to the block of pixels;

selecting a subset of the set of potential reference samples to be used as reference samples for the block of pixels, wherein the selected subset of reference samples comprises sets of n consecutive reference samples with m reference samples between the sets wherein variables n and m are positive integers; and

using the selected subset of reference samples to determine a DC prediction value for the block of pixels.

10. A storage medium according to claim 9 , the computer program code further configured to, with the processor, cause the apparatus to determine a prediction error for a pixel in the block of pixels on the basis of the DC prediction value and the value of the pixel in the block of pixels.

11. A non-transitory storage medium having stored thereon a computer executable program code for use by a decoder, said program code comprises instructions for:

receiving an encoded block of pixels;

determining a set of potential reference samples for the block of pixels, wherein the set of potential reference samples for the block of pixels comprises at least a part of the pixels of an encoded neighboring block which is adjacent to the block of pixels;

selecting a subset of the set of potential reference samples to be used as reference samples for the block of pixels, wherein the selected subset of reference samples comprises sets of n consecutive reference samples with m reference samples between the sets wherein variables n and m are positive integers;

determining reference samples for the encoded block of pixels;

using the determined reference samples to define a DC prediction value for the block of pixels;

receiving a prediction error for a pixel of the encoded block of pixels; and

reconstructing the pixel value on the basis of the DC prediction value and the prediction error.

12. An apparatus comprising:

means for receiving a block of pixels;

means for determining a set of potential reference samples for the block of pixels, wherein the set of potential reference samples for the block of pixels comprises at least a part of the pixels of an encoded neighboring block which is adjacent to the block of pixels;

means for selecting a subset of the set of potential reference samples to be used as reference samples for the block of pixels, wherein the selected subset of reference samples comprises sets of n consecutive reference samples with m reference samples between the sets wherein variables n and m are positive integers; and

means for using the selected subset of reference samples to determine a DC prediction value for the block of pixels.

13. The apparatus of claim 12 further comprising:

means for determining a prediction error for a pixel in the block of pixels on the basis of the DC prediction value and the value of the pixel in the block of pixels.

14. An apparatus comprising:

means for receiving an encoded block of pixels;

means for determining a set of potential reference samples for the block of pixels, wherein the set of potential reference samples for the block of pixels comprises at least a part of the pixels of an encoded neighboring block which is adjacent to the block of pixels;

means for selecting a subset of the set of potential reference samples to be used as reference samples for the block of pixels, wherein the selected subset of reference samples comprises sets of n consecutive reference samples with m reference samples between the sets wherein variables n and m are positive integers;

means for determining reference samples for the encoded block of pixels;

means for using the determined reference samples to define a DC prediction value for the block of pixels;

means for receiving a prediction error for a pixel of the encoded block of pixels; and

means for reconstructing the pixel value on the basis of the DC prediction value and the prediction error.