[Feature Request] Generate subchannel MSF based on data sector MSF

[HeroponRikiBestest]

This is mainly relevant for PC Hexalock-protected discs, which mess with MSF. Essentially, towards the end of the disc, they "roll back" MSF twice. Converting redumper .subcode into .sub, the MSF of the subchannels on the disc seem to match the MSF of the data sectors.

However, cuetoccd just generates what the subchannels "should" be, and thus they don't match the data sector MSF.

[mistydemeo]

I'd be happy to take a stab at it! How predictable is the pattern of "wrong" timecodes? Is it the same for every disc? Is there a way I can know to apply this based on the cue sheet, or would it make more sense to have a --hexalock flag that tells cue2ccd to write the subchannel this way?

[HeroponRikiBestest]

There's no predictable pattern in terms of where they appear, but they always match the data sector MSF. As far as I was imagining, it would be generated by taking the MSF from the data sector for its corresponding subchannel sector. I.e. when generating the subchannel for data sector 1, take the MSF from data sector 1 and use that, etc. Theoretically this wouldn't cause issues with any other "normal" discs, but could interfere with other protections like SecuROM which mess with intended subchannels in different ways, in case you wanted to add something like cue+bin+sbi support later. (Example of what i mean by that, albeit i think it has some issues on multi track images: https://pastebin.com/LaRfRrmD). That said, at least in that example, this could presumably just be disabled if an SBI is provided. There are one or two other protections like DiscGuard that also mess with subchannels, but I don't know enough about those yet to say how this would interact, and I'm not sure how viable subchannel generation for those would be anyways, since there's no equivalent of SBI for it like there is for securom and ps1 libcrypt.