KR20130045740A

KR20130045740A - ＤｅｌｔａＱｐｓｃａｌｉｎｇ method using ｐｒｅｄｉｃｔｉｏｎｍｏｄｅ in the surrounding ｂｌｏｃｋ

Info

Publication number: KR20130045740A
Application number: KR1020110110147A
Authority: KR
Inventors: 이배근; 권재철
Original assignee: 주식회사 케이티
Priority date: 2011-10-26
Filing date: 2011-10-26
Publication date: 2013-05-06

Abstract

When the prediction mode of the current CU / PU and the prediction mode of the left block / above block are different, when the Qp value of the neighboring block is predicted, there is a high probability that the dQp value becomes large. In the present invention, when a neighboring block and a current block have different prediction modes, a method of scaling and representing dQp is provided. In this case, as suggested by JCTVC-F495, by using dQp_scale larger than 1, the coding performance can be improved by reducing the amount of information signaling the dQp value. In particular, when the current block is in the inter mode, and the neighboring left block and the above block are in the intra mode, since the probability that the Qp value of the neighboring block is the same as the Qp value of the current block is small, the dQp value increases.

Description

ＤｅｌｔａＱｐｓｃａｌｉｎｇ method using ｐｒｅｄｉｃｔｉｏｎｍｏｄｅ in the surrounding ｂｌｏｃｋ {.}

The present invention relates to a prediction mode.

When the prediction mode of the current CU / PU and the prediction mode of the left block / above block are different, when the Qp value of the neighboring block is predicted, there is a high probability that the dQp value becomes large.

In the present invention, when a neighboring block and a current block have different prediction modes, a method of scaling and representing dQp is provided.

According to an embodiment of the present invention, a delta Qp scaling method using a prediction mode of a peripheral blcok is provided.

Encoding performance can be improved.

1 shows dQP = 1 with different dQP_scale.
2 illustrates a Qp_scale value according to a prediction type correlation between a neighboring block and a current block.

I. Existing Method

1. Adaptive dQp signaling [JCTVC-F495]

Existing methods currently use the method of obtaining Qp_prediction and transmitting the difference with the current Qp value (dQP). As shown in the following equation, multiplying dQP by dQP_scale reduces the amount of bits used to encode the value of dQP.

QP_curr = QP_pred + dQP * dQP_Scale

1 shows dQP = 1 with different dQP_scale.

II. Proposal method

1. Method of setting dQP_Scale of prediction according to prediction mode or intra / inter mode of neighboring block

If the prediction mode of the current block and the prediction mode of the current block and the left block of the current block are different, the prediction QP value is different from the prediction QP of the current block, and the difference is likely to be large. In this case, the dQP_scale value may be set to a value greater than 1 to reduce the dQP coded bit.

A method of setting a dQP_scale value according to a prediction mode or intra / inter mode correlation of a neighboring block and a current block is presented.

The dQP_scale value is determined according to the correlation between the left block and the above block. When the current block is in intra mode, dQP_scale may be applied differently depending on whether the left block and the above block are inter or intra.

The dQP_scale derivation method is as follows.

1.If (PredMode (A) = PredMode (L) = PredMode (Curr)) Qp_scale = 1

2.If (PredMode (A) = PredMode (Curr) and PredMode (L) ≠ PredMode (Curr)) Qp_scale = 1

3.If (PredMode (A) ≠ PredMode (Curr) and PredMode (L) = PredMode (Curr)) Qp_scale = 1

4.If (PredMode (A) = PredMode (L) ≠ PredMode (Curr)) Qp_scale = 2

Curr denotes current block, A denotes above block of Curr and L denotes left block of Curr.

2 illustrates a Qp_scale value according to a prediction type correlation between a neighboring block and a current block.

or

1.If (PredMode (A) = PredMode (L) = PredMode (Curr)) Qp_scale = 1

2.If (PredMode (A) = PredMode (Curr) and PredMode (L) ≠ PredMode (Curr)) Qp_scale = 2

3.If (PredMode (A) ≠ PredMode (Curr) and PredMode (L) = PredMode (Curr)) Qp_scale = 2

4.If (PredMode (A) = PredMode (L) ≠ PredMode (Curr)) Qp_scale = 3

III. Encoding Process

1. A new coding unit of the current frame is input.

A. Coding Unit is the basic unit of region segmentation used for Inter / Intra prediction. The CU is always square and its size can range from 8x8 Luma blocks to TB (Tree Block, 64x64). The CU may be recursively partitioned into four blocks of equal size starting from TB.

B. The prediction unit PU is a block smaller than a coding unit (CU), not necessarily square, and may be a rectangular block.

i. Intra prediction of a PU is basically performed in units of 2N * 2N and N * N blocks.

2. Generate a reference pixel for intra prediction.

A. The pixels on the rightmost vertical line of the left block adjacent to the current prediction block and the pixels on the bottom horizontal line of the top block are used to generate reference pixels. If the size of the prediction block is N, 2N pixels in each direction are used as reference pixels.

B. Reference pixels can be just written, smoothed, or signaled when smoothing.

i. For smoothing, use an Adaptive Intra Smoothing (AIS) filter. The filter coefficient uses one of [1,2,1], [1,1,4,1,1]. The latter filter provides a sharper interface.

ii. Signal whether to use a filter or not, and if so, what filter to use.

3. Determine the intra prediction mode.

A. Intra prediction mode is performed in PU units.

B. The optimal prediction mode is determined considering the relationship between the required bit rate and the distortion amount.

C. The number of prediction modes for the luma component according to the PU block size is as follows.

D. The prediction direction of intra prediction mode is as follows.

i. 0 generates adjacent block pixel values in the vertical direction, 1 in the horizontal direction, and 2 in the predicted block with the average brightness value (DC) of the current PU.

ii. The remaining modes predict the neighboring block pixel values according to the corresponding angles.

Find the prediction mode of the E. Chroma component.

4. Code the prediction mode of the current block.

i. Prediction mode is encoded for the Luma block and the Chroma block of the current block.

ii. Since the prediction mode of the current block has a high correlation with the prediction mode of the neighboring block, the bit amount is reduced by encoding the prediction mode of the current block using the prediction mode of the neighboring block.

iii. Determining the Most Probable Mode (MPM) of the current block and encoding the prediction mode of the current block using the MPM.

5. A residual signal is obtained by obtaining a difference in pixel units between the pixel value of the current block and the pixel value of the prediction block.

6. Transform and encode the residual signal.

A. The transcoding kernel uses 4x4, 8x8, 16x16, 32x32.

B. For n * n blocks, the conversion factor C is calculated as

C (n, n) = T (n, n) x B (n, n) x T (n, n) ^T

C. Quantize the transform coefficients.

i. If the current prediction unit is intra prediction, Qp is predicted (PredQp) according to the intra prediction mode. ,

ii. The dQp_scale value is set according to the correlation between the prediction type of the neighboring block and the prediction type of the current block.

1.If the same mode is used among Intra / Inter of the current block and neighboring blocks, set dQp_scale value to 1.

2. If the Intra / Inter moderk of the current block and neighboring blocks is not the same, set dQp_scale value to 2.

iii. A dQp value obtained by subtracting a Qp value PredQp predicted from Qp of the current block is encoded.

7. The RDO decides whether to send the residual signal or the conversion factor.

A. If the prediction is good, the residual signal can be transmitted without conversion coding.

B. Compare the cost functions before and after the conversion encoding and choose how the cost is minimized.

C. Signal the type of signal (Residual or transform coefficient) to be transmitted for the current block.

8. Scan the conversion factor.

9. Entropy code the scanned transform coefficients and intra prediction mode.

IV. Decoding process

1. Entropy decode the received bitstream.

A. Find the block type from the VLC table and get the prediction mode of the current block.

B. Determine whether the signal transmitted for the current block is residual or conversion factor.

C. Obtain the residual signal or transform coefficient for the current block.

2. An inverse scan of the entropy decoded residual signal or transform coefficient is performed to generate a two-dimensional block.

A. For residual signals, create residual blocks.

B. In the case of transform coefficients, generate transform blocks.

3. In case of transform coefficient, inverse quantization and inverse transform are performed to obtain residual block.

A. Perform dequantization.

i. Decode the dQp value.

ii. If the current prediction unit is intra prediction, Qp is predicted (PredQp) according to the intra prediction mode.

iii. The Qp_scale value is obtained by looking at the correlation between the neighboring block and the intra / inter mode of the current block.

iv. Get the Qp value of the current block. Qp = dQp + PredQp * Qp_scale

B. B (n, n) = T (n, n) x C (n, n) x T (n, n) ^T. Or B (m, n) = T (m, m) x C (m, n) x T (n, n) ^T.

C. Residual signal is obtained by inverse transformation.

4. Create a reference pixel.

A. When generating a reference pixel at the encoder, the decoder generates a reference pixel by referring to the signaled information about whether a smoothing filter was used or what type of filter was used.

B. Pixels on the rightmost vertical line of the left block that are already decoded and reproduced adjacent to the current prediction block and pixels on the bottom horizontal line of the upper block are used to generate the reference pixel.

C. Depending on the reference pixel generation method used in the encoder

i. If smoothed, use the Adaptive Intra Smoothing filter.

ii. The filter coefficient is selected from [1, 2, 1] and [1, 1, 4, 1, 1] using the filter type information.

5. Create a prediction block using the prediction mode.

A. A prediction block is generated using a reference pixel from the prediction mode of the entropy decoded current block.

B. The generation process of the prediction block is the same as the process used to determine the prediction mode of the encoder.

6. A prediction block is generated by adding the prediction block pixel value and the residual block pixel value.

Claims

A delta Qp scaling method using prediction mode of surrounding blcok.