Methods and apparatuses for filtering of ringing artifacts post decoding
View Patent ↗A technique to perform filtering of ringing artifacts is disclosed herein. An example apparatus may include a decoder configured to receive a bitstream, decode the bitstream into blocks, identify conditions in the blocks associated with generation of ringing artifacts, and filter the ringing artifacts from one or more of the blocks responsive to identification of the conditions by the decoder. An example method may include detecting conditions in a bitstream that lead to ringing artifacts, configuring a filter based on the conditions, and filtering the ringing artifacts from blocks of decoded bitstream.
1. An apparatus comprising:
a decode module configured to (i) receive a bitstream, (ii) generate a block by decoding the bitstream and (iii) extract a quantization parameter used to encode the block from the bitstream;
a maximum difference module coupled to the decode module, and configured to (i) receive the block and the quantization parameter from the decode module, and (ii) determine a first threshold of the block based on a plurality of pixels in the block and the quantization parameter; and
a de-ringing filter module coupled to the maximum difference module and the decode module, and configured to (i) receive the first threshold from the maximum difference module, (ii) receive the block from the decode module, (iii) determine a second threshold based on the first threshold, wherein the second threshold is higher than the first threshold, (iv) determine a weighting factor for a first pixel among the pixels in the block based on a comparison of (a) an absolute difference between the first pixel and a second pixel among the pixels in the block with (b) the first threshold and the second threshold and (v) filter the second pixel based on the weighting factor.
2. The apparatus of claim 1 , wherein the bitstream is encoded using an MPEG-2 compression format.
3. An apparatus comprising:
a decoder configured to (i) receive a bitstream, (ii) generate a plurality of blocks by decoding the bitstream and (iii) extract a plurality of quantization parameters used to encode the blocks from the bitstream; and
a processor coupled to the decoder and configured to (i) receive the blocks and the quantization parameters from the decoder, and (ii) determine a plurality of first thresholds of the blocks based on a plurality of pixels in each of the blocks and the quantization parameters, (iii) determine a plurality of second thresholds of the blocks based on the first thresholds, wherein the second threshold is higher than the first threshold, (iv) determine a weighting factor for a first pixel among the pixels in each of the blocks based on a comparison of (a) an absolute difference between the first pixel and a second pixel among the pixels in a same block with (b) the first threshold of the same block and the second threshold of the same block and (v) filter the second pixels based on the weighting factors.
4. A method for filtering ringing artifacts, comprising the steps of:
receiving a bitstream at a circuit;
generating a block by decoding the bitstream;
extracting a quantization parameter used to encode the block from the bitstream;
determining a first threshold of the block based on a plurality of pixels in the block and the quantization parameter;
determining a second threshold based on the first threshold, wherein the second threshold is higher than the first threshold;
determining a weighting factor for a first pixel among the pixels in the block based on a comparison of (i) an absolute difference between the first pixel and a second pixel among the pixels in the block with (ii) the first threshold and the second threshold; and
filtering the second pixel based on the weighting factor.
5. The method of claim 4 , wherein the determination of the first threshold comprises:
determining a maximum activity of the pixels of the block;
generating a combined value by combining the quantization parameter and the maximum activity; and
scaling the combined value to produce the first threshold.
6. The apparatus of claim 1 , wherein the determination of the first threshold comprises (i) determining a maximum activity of the pixels of the block, (ii) generating a combined value by combining the quantization parameter and the maximum activity and (iii) scaling the combined value to produce the first threshold.
7. The apparatus of claim 1 , wherein the weighting factor is set to a zero value while the absolute difference is greater than the second threshold.
8. The apparatus of claim 1 , wherein the weighting factor is set to a maximum value while the absolute difference is less than the first threshold.
9. The apparatus of claim 1 , wherein the weighting factor is based on an interpolation between the first threshold and the second threshold while the absolute difference is greater than the first threshold but less than the second threshold.
10. The apparatus of claim 3 , wherein the weighting factor is set to a zero value while the absolute difference is greater than the second threshold.
11. The apparatus of claim 3 , wherein the weighting factor is set to a maximum value while the absolute difference is less than the first threshold.
12. The apparatus of claim 3 , wherein the weighting factor is based on an interpolation between the first threshold and the second threshold while the absolute difference is greater than the first threshold but less than the second threshold.
13. The method of claim 4 , wherein the determination of the weighting factor comprises:
setting the weighting factor to a zero value while the absolute difference is greater than the second threshold;
setting the weighting factor to a maximum value while the absolute difference is less than the first threshold; and
determining the weighting factor based on an interpolation between the first threshold and the second threshold while the absolute difference is greater than the first threshold but less than the second threshold.
14. The method according to claim 13 , wherein the maximum value is based on an encoding format of the bitstream.
15. The method according to claim 4 , further comprising the steps of:
generating a strength parameter; and
adjusting a strength of the filtering of the second pixel based on the strength parameter.
16. The apparatus according to claim 1 , wherein (i) the maximum difference module is further configured to generate a strength parameter and (ii) the de-ringing filter module is further configured to (a) receive the strength parameter from the maximum difference module and (b) adjust a strength of the filtering of the second pixel based on the strength parameter.
17. The apparatus according to claim 8 , wherein the maximum value is based on an encoding format of the bitstream.
18. The apparatus according to claim 3 , wherein the processor is further configured to (i) generate a strength parameter and (ii) adjust a strength of the filtering of the second pixel based on the strength parameter.