Hi! If I'm not mistaken, Impulse tracker 1.x saves the volume envelope as a list of about 200 volume levels rather than saving the envelope node coordinates. At least it seems so looking at the old instrument format in ittech.txt. Now that I look further into it, IT v1.x does not seem to support panning or pitch envelopes. That means that the 25 node points saved per instrument after the 200 volume levels are also a description of the volume envelope, meaning the volume envelope is saved twice in the file - which is a bit odd. Can anyone confirm this? Thanks in advance.
You can completely ignore the level data, yes. I assume that it exists purely as a speed-up (pre-computing the linear interpolation equations rather than having to re-calculate them on every tick) for the player, and there is no good reason that it exists in the file itself, apart from making it easier to directly dump IT's internal memory structures into a file.
Thanks for clearing that up! Much appreciated, as always.