Separated default gmChannels for gpx

[Lukramancer]

Recently I've found some .gp files which work fine in GuitarPro but don't in TuxGuitar. Instruments of all tracks were replaced by one of the first track.

I've discovered that they are in GP7 format without specified general midi channels at MidiConnection element in score.gpif file in them.

In that case TuxGuitar reads default value 0 as midi channels. The same midi channel in all tracks causes all channels but the first one skip their initialization.

I made sure that the default channel value was one that had not yet been used.

[guiv42]

I tested with a 14-track .gp song, after manual deletion of the content of all PrimaryChannel and SecondaryChannel nodes:

• current behavior
  • all tracks are allocated to Grand Acoustic Piano
• with this PR
  • tracks are allocated somehow randomly to instruments
  • only the first 8 tracks are audible
  • the list of instruments defined in song is correct: user can re-allocate correctly the instruments to tracks
• with this PR + a limitation of number of channels to 16
  • tracks are allocated somehow randomly to instruments
  • tracks >= 8 are all allocated to the same instrument
  • all tracks are audible
  • but the list of instruments defined in song is incomplete, so it's more complex for user to re-allocate correctly the instruments

So, forget my comment and let's keep this PR unchanged.

[Lukramancer]

I'm not expert in GM at all. The thing about maximum channels amount is my oversight. I'll explore that issue more, cause I figured out one more thing. Using default secondary GM channel as 0 can double max instruments available. Can you please share that .gp file for future testing?

[guiv42]

Can you please share that .gp file for future testing?

Sure. I don't have so many .gp files, and only 1 with enough tracks, you can find it here