Support multiple video systems, and add PAL-M support #728
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When loading a .tbc file, ld-analyse will now check whether the corresponding _chroma.tbc file exists. If so, it'll load both of them, and give you the option of whether to view luma, chroma, or the sum of the two. (It doesn't decode them separately; that would be doable but a bit more complicated.) If you open a _chroma.tbc directly, it'll try to open both files if they exist, defaulting to the chroma view; otherwise it'll look for the luma JSON as before.
In the JSON, isSourcePal is replaced by a "system" string. In the library, this is converted to a VideoSystem enum; if "system" is not set, then the system is guessed from isSourcePal and fieldHeight, so the tools will still work with old files. PAL-M uses PAL colour on a 525-line line standard with fSC being close to but not the same as NTSC -- so in some senses it works like standard PAL, and in some senses like standard NTSC. Adjust all the system-dependent parts of the tools as needed, including filters. This was tested with a VHS tape decoded by vhs-decode. I've assumed that closed captions aren't supported on PAL-M, although there's no particular reason why they couldn't be; if this is needed in the future then we should probably move the CC fields out of the NTSC structure.
atsampson
added
enhancement
ld-decode-tools
happycube
approved these changes
May 22, 2022
simoninns
approved these changes
May 23, 2022
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CC @oyvindln, who kindly supplied a sample PAL-M VHS capture to test this with...
In the JSON,
isSourcePalis replaced by a"system"string. In the library, this is converted to aVideoSystemenum; if"system"is not set, then the system is guessed fromisSourcePalandfieldHeight, so the tools will still work with old files.PAL-M uses PAL colour on a 525-line line standard with fSC being close to but not the same as NTSC -- so in some senses it works like standard PAL, and in some senses like standard NTSC. Adjust all the system-dependent parts of the tools as needed, including filters.
To make testing this easier, it also adds better support for vhs-decode's separate
_chroma.tbcfiles in ld-analyse - it now loads both files if present, and lets you switch between Y, C or Y+C:(Note to self to update the JSON docs again if people are happy with this.)