Robust encoding/decoding of escape-coded pixels in palette mode
Approaches to robust encoding and decoding of escape-coded pixels in a palette mode are described. For example, sample values of escape-coded pixels in palette mode are encoded/decoded using a binarization process that depends on a constant value of quantization parameter (“QP”) for the sample values. Or, as another example, sample values of escape-coded pixels in palette mode are encoded/decoded using a binarization process that depends on sample depth for the sample values. Or, as still another example, sample values of escape-coded pixels in palette mode are encoded/decoding using a binarization process that depends on some other fixed rule. In example implementations, these approaches avoid dependencies on unit-level QP values when parsing the sample values of escape-coded pixels, which can make encoding/decoding more robust to data loss.
1. A computer system comprising a processor and memory that implement a media encoder system, the media encoder system comprising:
a buffer configured to store a picture; and
a media encoder configured to perform operations comprising receiving and encoding the picture, wherein the encoding the picture includes encoding a unit of the picture in a palette mode, the unit of the picture being encoded in a lossy manner, and wherein the encoding the unit of the picture in the palette mode includes, for an escape mode of the palette mode:
quantizing a sample value for a color component of the unit of the picture; and
encoding the quantized sample value for the color component of the unit of the picture using a k th -order Exponential-Golomb binarization of a syntax element that represents the quantized sample value for the color component of the unit of the picture, wherein the k th -order Exponential-Golomb binarization is independent of any unit-level quantization parameter (“QP”) for the unit of the picture, and wherein the encoding the quantized sample values includes:
mapping the quantized sample value for the color component of the unit of the picture to a string of one or more binary values, wherein the string of one or more binary values is a part of the k th -order Exponential-Golomb binarization; and
entropy coding the string of one or more binary values.
2. The computer system of claim 1 , wherein the unit of the picture is a coding unit (“CU”) in a slice of the picture.
3. The computer system of claim 1 , wherein the encoding the picture further includes encoding a second sample value in the escape mode of the palette mode, and wherein the encoding the second sample value includes:
mapping the second sample value to a second string of one or more binary values, wherein the second string is a part of a fixed-length binarization that depends on a sample depth of the second sample value; and
entropy coding the second string of one or more binary values.
4. The computer system of claim 1 , wherein k is a pre-determined number.
5. The computer system of claim 1 , further comprising:
a video source producing a video sequence of a screen capture content, the video sequence comprising the picture.
6. The computer system of claim 1 , wherein another syntax element indicates whether transform and quantization are bypassed for the unit of the picture, and wherein the other syntax element indicates a result of determining whether the unit of the picture is encoded in a lossless manner or the lossy manner.
7. Non-volatile memory storing computer-executable instructions for causing a processor, when programmed thereby, to perform operations comprising:
receiving encoded data for a picture; and
decoding the picture, wherein the decoding the picture includes decoding a unit of the picture in a palette mode, the unit of the picture having been encoded in a lossy manner, and wherein the decoding the unit of the picture in the palette mode includes, for an escape mode of the palette mode:
decoding a quantized sample value for a color component of the unit of the picture using a k th -order Exponential-Golomb binarization of a syntax element that represents the quantized sample value for the color component of the unit of the picture without any parsing dependency on a unit-level quantization parameter (“QP”) for the unit of the picture, including:
determining the k th -order Exponential-Golomb binarization by invoking a k th -order Exponential-Golomb binarization process; and
entropy decoding a string of one or more binary values for the quantized sample value for the color component of the unit of the picture, wherein the entropy decoding uses the k th -order Exponential-Golomb binarization; and
inverse quantizing the quantized sample value for the color component of the unit of the picture.
8. The non-volatile memory of claim 7 , wherein the unit of the picture is a coding unit (“CU”) in a slice of the picture.
9. The non-volatile memory of claim 7 , wherein the decoding the picture further includes decoding a second sample value in the escape mode of the palette mode, and wherein the decoding the second sample value includes:
determining a fixed-length binarization that depends on a sample depth of the second sample value; and
entropy decoding a second string of one or more binary values for the second sample value, wherein the entropy decoding uses the fixed-length binarization.
10. The non-volatile memory of claim 7 , wherein k is a pre-determined number.
11. The non-volatile memory of claim 7 , wherein k is 3.
12. The non-volatile memory of claim 7 , wherein another syntax element indicates whether transform and quantization are bypassed for the unit of the picture, and wherein the decoding the unit of the picture further includes, based on the other syntax element, determining whether the unit of the picture has been encoded in a lossless manner or the lossy manner.
13. In a computer system, a method comprising:
receiving encoded data for a picture; and
decoding the picture, wherein the decoding the picture includes decoding a unit of the picture in a palette mode, the unit of the picture having been encoded in a lossy manner, and wherein the decoding the unit of the picture in the palette mode includes, for an escape mode of the palette mode:
decoding a quantized sample value for a color component of the unit of the picture using a k th -order Exponential-Golomb binarization of a syntax element that represents the quantized sample value for the color component of the unit of the picture without any parsing dependency on a unit-level quantization parameter (“QP”) for the unit of the picture, including:
determining the k th -order Exponential-Golomb binarization by invoking a k th -order Exponential-Golomb binarization process; and
entropy decoding a string of one or more binary values for the quantized sample value for the color component of the unit of the picture, wherein the entropy decoding uses the k th -order Exponential-Golomb binarization; and
inverse quantizing the quantized sample value for the color component of the unit of the picture.
14. The method of claim 13 , wherein the unit of the picture is a coding unit (“CU”) in a slice of the picture.
15. The method of claim 13 , wherein the decoding the picture further includes decoding a second sample value in the escape mode of the palette mode, and wherein the decoding the second sample value includes:
determining a fixed-length binarization that depends on a sample depth of the second sample value; and
entropy decoding a second string of one or more binary values for the second sample value, wherein the entropy decoding uses the fixed-length binarization.
16. The method of claim 13 , wherein k is a pre-determined number.
17. The method of claim 16 , wherein k is 3.
18. The method of claim 13 , wherein another syntax element indicates whether transform and quantization are bypassed for the unit of the picture, and wherein the decoding the unit of the picture further includes, based on the other syntax element, determining whether the unit of the picture has been encoded in a lossless manner or the lossy manner.