Re-Recording

[Xargoyle]

Add a re-recording feature for longplay purposes.

[joevt]

What's a re-recording feature?
What's a longplay purpose?

[Xargoyle]

https://tasvideos.org/Glossary#ReRecordReRecording

It means one that can be used for longplaying video games like World of Longplays for example.

[dingusdev]

An interesting request, but this is not priority. I'd reckon it'd be a lot harder to implement this on a computer emulator than a console emulator.

[joevt]

I'd reckon it'd be a lot harder to implement this on a computer emulator than a console emulator.

Right. I think TAS requires cycle accurate deterministic code execution. The link https://tasvideos.org/Glossary#ReRecordReRecording says "Because the emulation is completely predictable, it works." That may be true for a Nintendo but not a Mac. For example, different displays or resolutions have different refresh rates which cause display interrupts at different times.
Everything has an interrupt on a Mac. Audio, ADB, disk drives, etc. Well, DingusPPC has a --deterministic mode created by @mihaip but I don't know if that is sufficient. We would probably have to disconnect host audio because that's performed by a different thread.

It may be possible to add a pause feature which saves the states of all devices and RAM so that the host can resume the guest at a later time or after a restart. The pause would save the modification date of the disk image so that it can warn if the disk image has been modified externally by something else since the pause occurred. This will guard against disk corruption caused by out of sync disk cache in the saved RAM.

A snapshot feature is more difficult. A snapshot allows rewinding the state of the guest to a previous save point. This would require a proprietary disk image format that can save multiple snapshots. Maybe a sparse disk image format to lower the size of each snapshot.

[Randrianasulu]

This would require a proprietary disk image format that can save multiple snapshots.

I wonder if earlier or current version of qcow(2) format from Qemu can be used for that? At least earlier (mid-2000) qemu was more of community project , not giant enterprise thing it is today ....