Update README.md, add GAX 1 support

Author: byvar

README.md

@@ -1,6 +1,21 @@
 # GaXM
 Experimental GAX (Shin'en GBA audio engine) to XM converter
 
-Many GAX features are not supported in XM. As such the resulting files will likely sound different from in-game.
+All GAX versions are supported, so it should be possible to create XM files for most games using this engine.
+However, many GAX features are not supported in XM. As such the resulting files will likely sound different from in-game.
 
-At the moment, GAX 1 is not yet supported.
+Some of these features are:
+
+* Tempo in XM is specified using a BPM and Speed value (= number of ticks per row). The tempo change effect either affects the BPM value (when parameter >= 32) or the Speed value (when parameter < 32), but not both. GAX's tempo system is different: it only uses a Speed value very similar to XM's (that matches XM's tempo when BPM is about 149-150). Because the tempo change effect can only affect the Speed value, it can be set to larger values than in XM. Additionally, to achieve that would require a non-integer speed value, compositions in GAX often change the tempo on each row. GAX includes a separate effect for this that starts this speed value alternating system and allows one to use different effects in the next rows. XM does not have this, so I translated this effect by using the closest single speed value that is faster. As a result, many GAX -> XM conversions are faster than the original track.
+
+* While XM processes one pattern at a time per channel, GAX processes two: the pattern specified for that channel and the pattern specified in the current instrument. Instrument patterns can advance at a different speed (again, number of ticks per row) than the regular pattern. These "instrument rows" include information like the sample (& corresponding pitch, loop info, etc.), relative note number, and 2 effects which include volume, changing the instrument pattern speed... Arpeggios are a great use case for this system, so they are often missing entirely from GAX -> XM conversions.
+
+* Of course, some that I haven't fully reverse-engineered yet. :)
+
+However, for some games these exports sound close to perfect. Most likely, they can be perfected by creating a custom GAX player using the GAX structs provided in [BinarySerializer.GBA.Audio](https://github.com/BinarySerializer/BinarySerializer.GBA.Audio).
+
+## Note
+If you download the repo as a zip folder the submodules won't be included, causing the project not to compile. To solve this, download the submodule repos as well and place them in the specified folders:
+* [BinarySerializer](https://github.com/BinarySerializer/BinarySerializer) (submodules/BinarySerializer)
+* [BinarySerializer.Audio](https://github.com/BinarySerializer/BinarySerializer.Audio) (submodules/BinarySerializer.Audio)
+* [BinarySerializer.GBA.Audio](https://github.com/BinarySerializer/BinarySerializer.GBA.Audio) (submodules/BinarySerializer.GBA.Audio)

src/GAX/GAXHelpers.cs

@@ -74,7 +74,7 @@ public static void ExportGAX(string basePath, string mainDirectory, IGAX_Song so
                 }
             }
             var h = song;
-            if (h.Info.SampleRate == 0) return;
+            if (h.Info.SampleRate == 0 && h.Info.Context.GetGAXSettings().MajorVersion >= 2) return;
 
 
             GAX_XMWriter xmw = new GAX_XMWriter();

src/Program.cs

@@ -103,6 +103,7 @@ private static void ParseROM(Options options) {
                         try {
                             IGAX_Song Song = null;
                             switch (gaxVersion) {
+                                case 1:
                                 case 2:
                                     Song = s.SerializeObject<GAX2_Song>(default, name: nameof(Song));
                                     break;
@@ -150,6 +151,7 @@ private static void ParseROM(Options options) {
                             s.DoAt(song.Offset, () => {
                                 IGAX_Song Song = null;
                                 switch (gaxVersion) {
+                                    case 1:
                                     case 2:
                                         Song = s.SerializeObject<GAX2_Song>(default, name: nameof(Song));
                                         break;