Processing function for the Q31 DCT4/IDCT4.
- Deprecated:
- Do not use this function. It will be removed in future versions.
- Parameters
-
[in] | S | points to an instance of the Q31 DCT4 structure. |
[in] | pState | points to state buffer. |
[in,out] | pInlineBuffer | points to the in-place input and output buffer. |
- Input an output formats
- Input samples need to be downscaled by 1 bit to avoid saturations in the Q31 DCT process, as the conversion from DCT2 to DCT4 involves one subtraction. Internally inputs are downscaled in the RFFT process function to avoid overflows. Number of bits downscaled, depends on the size of the transform. The input and output formats for different DCT sizes and number of bits to upscale are mentioned in the table below:
DCT Size | Input format | Output format | Number of bits to upscale |
2048 | 2.30 | 12.20 | 11 |
512 | 2.30 | 10.22 | 9 |
128 | 2.30 | 8.24 | 7 |