Simple PAL UV filter and PAL encoder enhancements #476
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The second assert trips with EBU Tech 3280-style sample layout, where the digital active area runs right up to the end of the line. It's not actually a problem to run off the end of the line, because we'll just be using the blanking data from the start of the next line (and there's always another line after the last active line).
This gives better vertical resolution, at the cost of not dealing with chroma phase errors. Thanks to Richard Russell for providing the specs for the filter from the BBC's original Transform PAL implementation. This only works with transform2d/3d at the moment, but in the future it'd be possible to add a luma notch filter, giving a pal1d mode.
The core of this is effectively the same, once the setup is done; it just needs to keep track of where 0H is for each line.
The count of lines in field 1 was wrong here, which meant that the Vsw state didn't flip between the last line of field 1 and the first of field 2.
Add a reference to Clarke for the intended characteristic.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
More work on the Transform PAL decoder:
Add
ld-chroma-decoder --simple-pal, which in Transform PAL mode uses a 1D UV filter that's equivalent to that in the original hardware decoder (better vertical resolution, but less resistant to phase errors).Make ld-chroma-encoder able to produce subcarrier-locked 4fSC output, including all the parts of the PAL signal that I didn't previously implement - syncs, burst suppression, halfline blanking. Also fix a couple of mistakes that made the output nonstandard. I've made this match EBU Tech 3280 as far as possible - each line in the TBC contains the Tech 3280 blanking samples followed by active samples.
The TBC library still needs some work to make the other tools understand 4fSC properly (see #242), but I have more of an idea of how to do this now...