Scan patterns for progressive video content
Tools and techniques for applying scan patterns during encoding and decoding of progressive video are described. For example, a video decoder entropy decodes transform coefficients in a one-dimensional array and scans the transform coefficients into a block according to a scan pattern. The block is 8×4, and the scan pattern biases the vertical direction for at least the lowest frequency AC coefficients in the horizontal and vertical directions. Or, the block is 4×8, and the scan pattern biases the horizontal direction for at least the lowest frequency AC coefficients in the horizontal and vertical directions. A corresponding video encoder applies the scan patterns to scan transform coefficients from blocks to one-dimensional arrays.
1. A method for transforming video information using a computing device that implements a video encoder, the method comprising:
with the computing device that implements the video encoder:
scanning a 4×8 block of transform coefficients into a one-dimensional array according to a scan pattern, wherein the 4×8 block is 4 coefficients in a horizontal direction by 8 coefficients in a vertical direction, wherein the scan pattern is adapted for 4×8 inter-coded blocks of progressive video, the 4×8 inter-coded blocks being encoded without using AC prediction, wherein the scan pattern biases the horizontal direction for at least the lowest frequency AC coefficients in the horizontal and vertical directions, and wherein the scan pattern is:
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13
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8
17
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24
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26
9
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28
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29
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18
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31 ; and
entropy coding the transform coefficients in the one-dimensional array.
2. The method of claim 1 further comprising:
with the computing device that implements the video encoder:
scanning a 8×4 block of transform coefficients into a second one-dimensional array according to a second scan pattern, wherein the 8×4 block is 8 coefficients in the horizontal direction by 4 coefficients in the vertical direction, wherein the second scan pattern is adapted for 8×4 inter-coded blocks of progressive video, wherein the second scan pattern biases the vertical direction for at least the lowest frequency AC coefficients in the horizontal and vertical directions in the 8×4 block, and wherein second scan pattern is:
0
2
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7
10
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21
27
1
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11
13
17
24
29
3
9
12
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30
8
16
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31 ; and
entropy coding the transform coefficients in the second one-dimensional array.
3. The method of claim 1 wherein the entropy coding includes run/level/last coding, and wherein the bias reduces average count of transform coefficients before the last non-zero transform coefficient in the second one-dimensional array.
4. The method of claim 1 wherein the scan pattern is adapted for strong vertical edges.
5. The method of claim 1 wherein the entropy coding includes run/level/last coding, and wherein the bias reduces average count of transform coefficients before the last non-zero transform coefficient in the one-dimensional array.
6. The method of claim 1 wherein, depending on profile, the video encoder uses one scan pattern per transform size for inter-coded blocks of progressive video.
7. A method for transforming encoded video information using a computing device that implements a video decoder, the method comprising:
with the computing device that implements the video decoder:
entropy decoding transform coefficients in a one-dimensional array; and
scanning the transform coefficients into a 4×8 block according to a scan pattern, wherein the 4×8 block is 4 coefficients in a horizontal direction by 8 coefficients in a vertical direction, wherein the scan pattern is adapted for 4×8 inter-coded blocks of progressive video, the 4×8 inter-coded blocks having been encoded without using AC prediction, wherein the scan pattern biases the horizontal direction for at least the lowest frequency AC coefficients in the horizontal and vertical directions, and wherein the scan pattern is:
0
1
3
13
2
4
8
17
5
6
11
24
7
10
15
26
9
14
20
28
12
19
23
29
16
21
25
30
18
22
27
31.
8. The method of claim 7 further comprising:
with the computing device that implements the video decoder:
entropy decoding transform coefficients in a second one-dimensional array; and
scanning the transform coefficients from the second one-dimensional array into a 8×4 block according to a second scan pattern, wherein the 8×4 block is 8 coefficients in the horizontal direction by 4 coefficients in the vertical direction, wherein the second scan pattern is adapted for 8×4 inter-coded blocks of progressive video, wherein the second scan pattern biases the vertical direction for at least the lowest frequency AC coefficients in the horizontal and vertical directions in the 8×4 block, and wherein the second scan pattern is:
0
2
4
7
10
14
21
27
1
5
6
11
13
17
24
29
3
9
12
15
18
22
25
30
8
16
19
20
23
26
28
31.
9. The method of claim 8 wherein the entropy decoding includes run/level/last decoding.
10. The method of claim 7 wherein the scan pattern is adapted for strong vertical edges.
11. The method of claim 7 wherein the entropy decoding includes run/level/last decoding.
12. The method of claim 7 wherein, depending on profile, the video decoder uses one scan pattern per transform size for inter-coded blocks of progressive video.