Devices and methods for signaling sample adaptive offset (SAO) parameters
View Patent ↗Systems and methods that improve video quality by signaling of parameters in a sample adaptive offset (SAO) process are disclosed. The methods and systems described herein generally pertain to video processing such as video encoders and decoders.
1. A method for sample adaptive offset (SAO) filtering and SAO parameter signaling in a video encoder, the method comprising:
determining SAO parameters for largest coding units (LCUs) of a reconstructed picture using a merge flag by:
copying SAO parameters for all color components of a current LCU from corresponding color components of a left neighboring LCU if the merge flag indicates to use merge and a left neighboring LCU is available;
copying SAO parameters for one or more color components of the current LCU from corresponding color components of the above neighboring LCU if the merge flag indicates to use merge and the left neighboring LCU is not available; and
if the merge flag does not indicate to use merge, explicitly signaling SAO parameters for each luminance and chrominance color component of the current LCU using a luminance merge flag and at least one chrominance merge flag; and
applying SAO filtering to the reconstructed picture according to the SAO parameters.
2. The method of claim 1 , wherein the SAO parameters comprise an indicator of an SAO filter type and a plurality of SAO offsets.
3. The method of claim 1 , further comprising:
encoding LCU specific SAO information for each LCU of the reconstructed picture in an encoded video bit stream.
4. The method of claim 3 , wherein the LCU specific SAO information consists of values of the SAO parameters.
5. The method 1 , wherein explicitly signaling SAO parameters for each luminance and chrominance color component of the current LCU comprises determining for each color component if an SAO flag is on.
6. The method of claim 5 , wherein if an SAO flag is on for a color component, the explicitly signaling comprises transmitting SAO parameters for the color component.
7. The method of claim 5 , wherein if the SAO flag is off for a color component, the explicitly signaling comprises not transmitting SAO parameters for the color component.
8. The method of claim 1 , wherein using a merge flag to indicate if SAO parameters are copied from a neighboring LCU for all or none of the color components results in a bit savings relative to using individual merge flags per color component.
9. The method of claim 8 , wherein the bit savings is two or four bits.
10. The method of claim 1 , wherein the merge flag is explicitly signaled by the encoder.
11. The method of claim 1 , wherein the merge flag is inferred by a decoder.
12. The method of claim 11 , wherein an immediate left neighboring LCU and an immediate above neighboring LCU of the current LCU use identical SAO parameters, a merge flag associated with one of the neighboring LCUs indicates that merge is not selected.
13. The method of claim 1 , wherein the method is implemented on a computer having a processor and a memory coupled to said processor, wherein at least some of the steps are performed using said processor.
14. A method for sample adaptive offset (SAO) filtering in a video decoder, the method comprising:
decoding largest coding unit (LCU) specific SAO information for an LCU from an encoded video bit stream; and
determining SAO parameters for the LCU from the LCU specific SAO information using a merge flag by:
copying SAO parameters for all color components of the LCU from corresponding color components of a left neighboring LCU if the merge flag indicates to use merge and a left neighboring LCU is available;
copying SAO parameters for one or more color components of the LCU from corresponding color components of the above neighboring LCU if the merge flag indicates to use merge and the left neighboring LCU is not available; and
if the merge flag does not indicate to use merge, explicitly signaling SAO parameters for each luminance and chrominance color component of the LCU using a luminance merge flag and at least one chrominance merge flag.
15. The method of claim 14 , wherein the SAO parameters comprise an indicator of an SAO filter type and a plurality of SAO offsets.
16. The method of claim 14 , wherein the LCU specific SAO information consists of values of the SAO parameters.
17. The method 14 , wherein explicitly signaling SAO parameters for each luminance and chrominance color component of the LCU comprises determining for each color component if an SAO flag is on.
18. The method of claim 17 , wherein if an SAO flag is on for a color component, the explicitly signaling comprises transmitting SAO parameters for the color component.
19. The method of claim 17 , wherein if the SAO flag is off for a color component, the explicitly signaling comprises not transmitting SAO parameters for the color component.
20. The method of claim 14 , wherein using a merge flag to indicate if SAO parameters are copied from a neighboring LCU for all or none of the color components results in a bit savings relative to using individual merge flags per color component.
21. The method of claim 20 , wherein the bit savings is two or four bits.
22. The method of claim 14 , wherein the merge flag is explicitly signaled by an encoder.
23. The method of claim 14 , wherein the merge flag is inferred by the decoder.
24. The method of claim 23 , wherein an immediate left neighboring LCU and an immediate above neighboring LCU of the current LCU use identical SAO parameters, and a merge flag associated with one of the neighboring LCUs indicates that merge is not selected.
25. An apparatus for encoding video data having a plurality of pictures, using sample adaptive offset (SAO), the apparatus comprising a video encoder configured to:
determine SAO parameters for largest coding units (LCUs) of a reconstructed picture using a merge flag by:
copying SAO parameters for all color components of a current LCU from corresponding color components of a left neighboring LCU if the merge flag indicates to use merge and a left neighboring LCU is available;
copying SAO parameters for one or more color components of the current LCU from corresponding color components of the above neighboring LCU if the merge flag indicates to use merge and the left neighboring LCU is not available; and
if the merge flag does not indicate to use merge, explicitly signaling SAO parameters for each luminance and chrominance color component of the current LCU using a luminance merge flag and at least one chrominance merge flag; and
apply SAO filtering to the reconstructed picture according to the SAO parameters.
26. The apparatus of claim 25 , wherein the apparatus comprises at least one of:
an integrated circuit;
a microprocessor; and
a wireless communication device that includes the video encoder.
27. An apparatus for decoding an encoded video bit stream having a plurality of pictures, the apparatus comprising a video decoder configured to:
decode largest coding unit (LCU) specific SAO information for an LCU from an encoded video bit stream; and
determine SAO parameters for the LCU from the LCU specific SAO information using a merge flag by:
copying SAO parameters for all color components of the LCU from corresponding color components of a left neighboring LCU if the merge flag indicates to use merge and a left neighboring LCU is available;
copying SAO parameters for one or more color components of the LCU from corresponding color components of the above neighboring LCU if the merge flag indicates to use merge and the left neighboring LCU is not available; and
if the merge flag does not indicate to use merge, explicitly signaling SAO parameters for each luminance and chrominance color component of the LCU using a luminance merge flag and at least one chrominance merge flag.
28. The apparatus of claim 27 , wherein the apparatus comprises at least one of:
an integrated circuit;
a microprocessor; and
a wireless communication device that includes the video decoder.