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1. About the Video and Vision Processing Suite
2. Getting Started with the Video and Vision Processing IPs
3. Video and Vision Processing IPs Functional Description
4. Video and Vision Processing IP Interfaces
5. Video and Vision Processing IP Registers
6. Video and Vision Processing IPs Software Programming Model
7. Protocol Converter Intel® FPGA IP
8. 3D LUT Intel® FPGA IP
9. AXI-Stream Broadcaster Intel® FPGA IP
10. Chroma Key Intel® FPGA IP
11. Chroma Resampler Intel® FPGA IP
12. Clipper Intel® FPGA IP
13. Clocked Video Input Intel® FPGA IP
14. Clocked Video to Full-Raster Converter Intel® FPGA IP
15. Clocked Video Output Intel® FPGA IP
16. Color Space Converter Intel® FPGA IP
17. Deinterlacer Intel® FPGA IP
18. FIR Filter Intel® FPGA IP
19. Frame Cleaner Intel® FPGA IP
20. Full-Raster to Clocked Video Converter Intel® FPGA IP
21. Full-Raster to Streaming Converter Intel® FPGA IP
22. Generic Crosspoint Intel® FPGA IP
23. Genlock Signal Router Intel® FPGA IP
24. Guard Bands Intel® FPGA IP
25. Interlacer Intel® FPGA IP
26. Mixer Intel® FPGA IP
27. Pixels in Parallel Converter Intel® FPGA IP
28. Scaler Intel® FPGA IP
29. Stream Cleaner Intel® FPGA IP
30. Switch Intel® FPGA IP
31. Tone Mapping Operator Intel® FPGA IP
32. Test Pattern Generator Intel® FPGA IP
33. Video Frame Buffer Intel® FPGA IP
34. Video Streaming FIFO Intel® FPGA IP
35. Video Timing Generator Intel® FPGA IP
36. Warp Intel® FPGA IP
37. Design Security
38. Document Revision History for Video and Vision Processing Suite User Guide
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28.3.2. Coefficient Quantization
The scaler IP implements the filters when you select Polyphase algorithm using fixed-point logic, so you must supply the filter coefficients in a fixed-point format. You define the format for the coefficients with parameters that select whether they are signed or unsigned, the number of integer bits, and the number of fraction bits.
- Signed or unsigned: if you want to represent negative coefficients, turn on Use signed vertical coefficients. If all coefficients are positive values, reduce logic and turn off Use signed vertical coefficients.
- Integer bits: the number of integer bits defines the maximum value that can be represented.
- Fraction bits: the number of fraction bits defines the precision with which the IP can convert floating-point coefficients into the fixed-point format.
The overall bit width of each coefficient is the sum of the integer and fraction bits, plus one extra bit for signed coefficients. When using Lanczos coefficients, Intel recommends the following settings:
- Turn on Use signed vertical coefficients as the Lanczos function for any number of lobes greater than 1 requires negative values, so the coefficients must be signed.
- Use 1 integer bit as the maximum value required for any Lanczos coefficient is 1.0
- Use between 6 and 8 fraction bits.
Typically, the filter coefficients produce noninteger floating-point values. To convert each floating-point coefficient into its closest quantized representation in the selected fixed-point format:
- Multiply each coefficient by 2 frac , where frac is the number of fraction bits you select
- Apply float to integer conversion to each coefficient
However, small errors in the coefficient values introduced by the quantization process can accumulate so that the coefficients in each phase no longer sum to their intended value. Generally, the coefficients in any phase should sum to exactly 1.0. Any value greater than 1.0 increases the overall brightness of the resulting image. Any value less than 1.0 reduces the brightness. The coefficients can sum to more or less than 1.0 if you want a brighter or darker image. You should still ensure your coefficients sum to your original, intended value post quantization. To restore the coefficients to values that sum to the intended value:
Figure 60. Restore Coefficient Values
float quantization_error = 0.0;
for (int j = 0; j < taps; j++) {
quantization_error += original_float_coeff[j] - ((float)quant_coeff[j]);
if (quantization_error < -0.5) {
quant_coeff[j]--;
quantization_error += 1.0;
} else {
if (quantization_error > -0.5) {
quant_coeff[j]++;
quantization_error -= 1.0;
}
}
}