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| #### 14.2 Inverse Transforms {#h-14-02} |
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| If the Y2 residue block exists (i.e., the macroblock luma mode is not |
| `SPLITMV` or `B_PRED`), it is inverted first (using the inverse WHT) and |
| the element of the result at row i, column j is used as the 0th |
| coefficient of the Y subblock at position (i, j), that is, the Y |
| subblock whose index is (i * 4) + j. As discussed in Section 13, if |
| the luma mode is `B_PRED` or `SPLITMV`, the 0th Y coefficients are part |
| of the residue signal for the subblocks themselves. |
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| In either case, the inverse transforms for the sixteen Y subblocks |
| and eight chroma subblocks are computed next. All 24 of these |
| inversions are independent of each other; their results may (at least |
| conceptually) be stored in 24 separate 4x4 arrays. |
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| As is done by the reference decoder, an implementation may wish to |
| represent the prediction and residue buffers as macroblock-sized |
| arrays (that is, a 16x16 Y buffer and two 8x8 chroma buffers). |
| Regarding the inverse DCT implementation given below, this requires a |
| simple adjustment to the address calculation for the resulting |
| residue pixels. |
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