NTSC chroma-encoder filter changes #760
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Adds a new chroma-mode, 'narrowband-q' to low-pass the Q component. Obsolete, but interesting for testing.
Change the filter used in the wideband-yuv/yiq modes to one suggested by Clarke for NTSC. Small PSNR improvement, up to 0.03 dB.
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Looks good to me - thanks! As you've been thinking about NTSC I/Q filters, do you have any suggestions for the ones in the NTSC decoder ( |
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--chroma-mode narrowband-qThis low-passes the Q channel such that it uses about half the bandwidth of the I channel. Non-equiband Y'IQ encoder/decoders were never widespread because of the extra complexity according to Poynton. Including it here for testing/completeness.
NTSC uses a different chroma low-pass than PAL for the wideband channels. Use the filter suggested by Clarke.
While neither of these two filters from Clarke quite match the filter template, anything I created in Iowa Hills that did meet the spec was more complex and ended up lowering PSNR vs. Clarke. DSP gurus are welcome to revisit this.