Fix chroma encoding in NTSCEncoder #789
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The 33-degree (or 57-degree) phase offset wasn't being added consistently, so the output samples didn't have the phase relationship the non-adaptive NTSC encoder expected. Rework prevCycles so that it's taken care of there, which then makes the rest of the code look more like the PAL version. Output the phaseID metadata field as 1-based, not 0-based -- this was the reason for the odd behaviour with the third field. For both PAL and NTSC, add a note about which samples are included in each line and how it differs from what ld-decode outputs. Finally, remove the 10-degree offset in Comb, since the phase relationship between the burst and chroma is now correct (patch from @oyvindln).
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Looks good to me. Thanks! |
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This should fix the encoding problem identified in the discussion for #787 - I ended up reworking how it figures out the phase offset for each sample, and fixing how it outputs phaseID to the metadata. This includes @oyvindln's change to Comb from #787 so the tests will pass (but the other change in #787 should rebase cleanly on top of this).
(Note that the output is still offset to the right when compared with ld-decode's output for both PAL and NTSC - this is because it's following SMPTE 244M/EBU Tech 3280 by having each line contain all the blanking samples, then all the active samples, whereas ld-decode starts each line with the sample immediately before 0H.)
CC @oyvindln and @ifb.