Low complexity coding based on dynamic mode decision branching

1. A method for video coding, comprising:

calculating a first sum of absolute difference (SAD) value between a coding unit (CU) block and a first corresponding block in a reference frame;

defining branching conditions for branching of CU sizes based at least in part on the first SAD value, the branching conditions comprising a background condition and a homogeneous condition;

detecting the background condition in response to the first SAD value of the CU block being less than a first threshold background value;

detecting the homogeneous condition in response to a second SAD value of a sub-block of the CU block being between upper and lower homogeneous threshold values based at least in part on the first SAD value; and

determining the branching of the CU sizes based on the detection of the background condition or the homogeneous condition.

2. The method of claim 1 , wherein:

the upper homogeneous threshold value equals C u *(first SAD value)/4, wherein C d is greater than 1; and

the lower homogeneous threshold value equals C d *(first SAD value)/4, wherein C d is less than 1.

3. The method of claim 1 , wherein defining the branching conditions for the branching of CU sizes comprises:

defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition;

defining the branching conditions for a second branch to comprise satisfaction of: (i) the second SAD value of the sub-block being less than a second threshold background value; or (ii) the second SAD value of the sub-block being between upper and lower homogeneous threshold values based at least in part on the first SAD value; and

defining the branching conditions for a third branch to comprise non-satisfaction of the branching conditions for the first and second branches.

4. The method of claim 1 , wherein defining the branching conditions for the branching of CU sizes comprises:

defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition;

defining the branching conditions for a second branch to comprise satisfaction of: (i) the second SAD value of the sub-block being less than a second threshold background value; or (ii) the third SAD value of a sub-sub block of the sub-block being between upper and lower homogeneous threshold values based at least in part on the second SAD value; and

defining the branching conditions for a third branch to comprise non-satisfaction of the branching conditions for the first and second branches.

5. The method of claim 1 , wherein defining the branching conditions for the branching of CU sizes comprises:

defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition; and

defining the branching conditions for a second branch to comprise non-satisfaction of the branching conditions for the first branch.

6. The method of claim 1 , further comprising performing dynamic mode decision (DMD) branching for a largest coding unit (LCU) based on checking a subset of the CU sizes according to the branching of the CU sizes.

7. The method of claim 6 , further comprising (i) selecting a coding mode for a coding tree unit (CTU) or (ii) performing motion estimation, based at least in part on the DMD branching for the LCU.

8. The method of claim 6 , further comprising encoding video data based on performing block-based processing of the video data according to the DMD branching for the LCU, the block-based processing comprising:

determining prediction blocks based on the DMD branching for the LCU;

calculating residuals based on subtracting the prediction blocks from original pixels of the video data;

forward transforming the calculated residuals into coefficients; and

quantizing and entropy encoding the coefficients.

9. The method of claim 6 , further comprising decoding video data based on performing block-based processing of the video data according to the DMD branching for the LCU, the block-based processing comprising:

entropy decoding and de-quantizing the received coefficients;

calculating residuals based on inverse transforming the entropy-decoded, de-quantized coefficients;

determining prediction blocks based on the DMD branching for the LCU; and

forming reconstructed pixels based on adding the calculated residuals to the prediction blocks.

10. The method of claim 1 , the method being executable on a wireless communication device, wherein the device comprises:

a memory configured to store video data;

a processor configured to execute instructions to process the video data stored in said memory; and

a transmitter configured to transmit encoded video data using a coding mode based upon CU sizes as determined by the branching conditions.

11. The method of claim 10 , wherein the wireless communication device is a wireless telephone and the encoded video data is transmitted by the transmitter and modulated according to a wireless communication standard.

12. An apparatus for video coding, comprising:

a memory unit configured to store video data; and

a video encoder in communication with the memory unit, the video encoder configured to:

calculate a first sum of absolute difference (SAD) value between a coding unit (CU) block and a first corresponding block in a reference frame;

define branching conditions for branching of CU sizes based at least in part on the first SAD value, the branching conditions comprising a background condition and a homogeneous condition;

detect the background condition in response to the first SAD value of the CU block being less than a first threshold background value;

detect the homogeneous condition in response to a second SAD value of a sub-block of the CU block being between upper and lower homogeneous threshold values based at least in part on the first SAD value; and

determine the branching of the CU sizes based on the detection of the background condition or the homogeneous condition.

13. The apparatus of claim 12 , wherein:

the upper homogeneous threshold value equals C u *(first SAD value)/4, wherein C d is greater than 1; and

the lower homogeneous threshold value equals C d *(first SAD value)/4, wherein C d is less than 1.

14. The apparatus of claim 12 , wherein the video encoder is configured to define the branching conditions for the branching of CU sizes based on:

defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition;

defining the branching conditions for a second branch to comprise satisfaction of: (i) the second SAD value of the sub-block being less than a second threshold background value; or (ii) the second SAD value of the sub-block being between upper and lower homogeneous threshold values based at least in part on the first SAD value; and

defining the branching conditions for a third branch to comprise non-satisfaction of the branching conditions for the first and second branches.

15. The apparatus of claim 12 , wherein the video encoder is configured to define the branching conditions for the branching of CU sizes based on:

defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition;

defining the branching conditions for a second branch to comprise satisfaction of: (i) the second SAD value of the sub-block being less than a second threshold background value; or (ii) the third SAD value of a sub-sub block of the sub-block being between upper and lower homogeneous threshold values based at least in part on the second SAD value; and

defining the branching conditions for a third branch to comprise non-satisfaction of the branching conditions for the first and second branches.

16. The apparatus of claim 12 , wherein the video encoder is configured to define the branching conditions for the branching of CU sizes based on:

defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition; and

defining the branching conditions for a second branch to comprise non-satisfaction of the branching conditions for the first branch.

17. The apparatus of claim 12 , wherein the video encoder is further configured to perform dynamic mode decision (DMD) branching for a largest coding unit (LCU) based on checking a subset of the CU sizes according to the branching of the CU sizes.

18. The apparatus of claim 17 , wherein the video encoder is further configured to (i) select a coding mode for a coding tree unit (CTU) or (ii) perform motion estimation, based at least in part on the DMD branching for the LCU.

19. The apparatus of claim 12 , wherein the device is a wireless communication device, further comprising:

a transmitter configured to transmit encoded video data using a coding mode based upon CU sizes as determined by the branching conditions.

20. The apparatus of claim 19 , wherein the wireless communication device is a wireless telephone and the encoded video data is transmitted by the transmitter and modulated according to a wireless communication standard.

21. An apparatus for video coding, comprising:

means for calculating a first sum of absolute difference (SAD) value between a coding unit (CU) block and a first corresponding block in a reference frame;

means for defining branching conditions for branching of CU sizes based at least in part on the first SAD value, the branching conditions comprising a background condition and a homogeneous condition;

means for detecting the background condition in response to the first SAD value of the CU block being less than a first threshold background value;

means for detecting the homogeneous condition in response to a second SAD value of a sub-block of the CU block being between upper and lower homogeneous threshold values based at least in part on the first SAD value; and

means for determining the branching of the CU sizes based on the detection of the background condition or the homogeneous condition.

22. The apparatus of claim 21 , wherein:

the upper homogeneous threshold value equals C u *(first SAD value)/4, wherein C d is greater than 1; and

the lower homogeneous threshold value equals C d *(first SAD value)/4, wherein C d is less than 1.

23. The apparatus of claim 21 , wherein the means for defining branching conditions for branching of CU sizes comprises:

means for defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition;

means for defining the branching conditions for a second branch to comprise satisfaction of: (i) the second SAD value of the sub-block being less than a second threshold background value; or (ii) the second SAD value of the sub-block being between upper and lower homogeneous threshold values based at least in part on the first SAD value; and

means for defining the branching conditions for a third branch to comprise non-satisfaction of the branching conditions for the first and second branches.

24. The apparatus of claim 21 , wherein the means for defining branching conditions for branching of CU sizes comprises:

means for defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition;

means for defining the branching conditions for a second branch to comprise satisfaction of: (i) the second SAD value of the sub-block being less than a second threshold background value; or (ii) the third SAD value of a sub-sub block of the sub-block being between upper and lower homogeneous threshold values based at least in part on the second SAD value; and

means for defining the branching conditions for a third branch to comprise non-satisfaction of the branching conditions for the first and second branches.

25. The apparatus of claim 21 , wherein the means for defining branching conditions for branching of CU sizes comprises:

means for defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition; and

means for defining the branching conditions for a second branch to comprise non-satisfaction of the branching conditions for the first branch.

26. The apparatus of claim 21 , further comprising means for performing dynamic mode decision (DMD) branching for a largest coding unit (LCU) based on checking a subset of the CU sizes according to the branching of the CU sizes.

27. The apparatus of claim 26 , further comprising at least one of: (i) means for selecting a coding mode for a coding tree unit (CTU) based at least in part on the DMD branching for the LCU; or (ii) means for performing motion estimation based at least in part on the DMD branching for the LCU.

28. A non-transitory computer readable medium comprising code that, when executed, causes an apparatus to perform a process comprising:

calculating a first sum of absolute difference (SAD) value between a coding unit (CU) block and a first corresponding block in a reference frame;

defining branching conditions for branching of CU sizes based at least in part on the first SAD value, the branching conditions comprising a background condition and a homogeneous condition;

detecting the background condition in response to the first SAD value of the CU block being less than a first threshold background value;

detecting the homogeneous condition in response to a second SAD value of a sub-block of the CU block being between upper and lower homogeneous threshold values based at least in part on the first SAD value; and

determining the branching of the CU sizes based on the detection of the background condition or the homogeneous condition.

29. The non-transitory computer readable medium of claim 28 , further comprising code that, when executed, causes the apparatus to define the branching conditions for the branching of CU sizes based on:

defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition; and

defining the branching conditions for a second branch to comprise non-satisfaction of the branching conditions for the first branch.

30. The non-transitory computer readable medium of claim 28 , further comprising code that, when executed, causes the apparatus to define the branching conditions for the branching of CU sizes based on:

defining the branching conditions for a first branch to comprise satisfaction of the background condition or the homogeneous condition;

defining the branching conditions for a second branch to comprise satisfaction of: (i) the second SAD value of the sub-block being less than a second threshold background value; or (ii) the second SAD value of the sub-block being between upper and lower homogeneous threshold values based at least in part on the first SAD value; and

defining the branching conditions for a third branch to comprise non-satisfaction of the branching conditions for the first and second branches.