Instrument sample loop points, correct pitch interpretation

scripts/loaders/sound_loader.gd

@@ -25,6 +25,14 @@ const MAX_16B = 1 << 16
 func unsigned16_to_signed(unsigned):
 	return (unsigned + MAX_15B) % MAX_16B - MAX_15B
 
+func get_reference_pitch_samplerate(tuning1: int, tuning2: int = 0) -> int:
+	# This is non-trivial and subject to change
+	var pitch_scale = tuning1/256.0 + tuning2/65536.0
+	if tuning1 < 0x80:
+		pitch_scale += 1.0
+	return int(pitch_scale * 36000)
+	# return (unsigned16_to_signed(pitch) + 0x8000) * 32000/4096
+
 func process_sample(mantissa: int, exponent: int) -> int:
 	# For filter arithmetic the samples need to be in signed form.
 	# Sign-extend
@@ -80,7 +88,7 @@ func make_sample(rom: File, size: int, sample_rate: int) -> AudioStreamSample:
 				for i in range(samples.size()-8, samples.size()):
 					samples[i] = clamp_short(samples[i] + (samples[i-1]*115)/64 - (samples[i-2]*13)/16)
 		if end:
-			print('End flag on packet')
+			# print('End flag on packet')
 			break
 	var audio_data = PoolByteArray()
 	for i in range(2, samples.size()):
@@ -92,22 +100,34 @@ func make_sample(rom: File, size: int, sample_rate: int) -> AudioStreamSample:
 
 func get_inst_sample_data(rom: File, id: int) -> AudioStreamSample:
 	rom.seek(INST_SR + (id*2))
-	var sample_rate := (rom.get_16() * 32000)/4096
+	var tuning1 := rom.get_8()
+	var tuning2 := rom.get_8()
+	var sample_rate := get_reference_pitch_samplerate(tuning1)
+
+	rom.seek(INST_LOOP + (id*2))
+	var loop_start_packet := rom.get_16()/9  # Note that Instrument $1F Steel Guitar has a length of $088B but a loop point of $088D which is 243.22... packets. Luckily it doesn't matter.
+
 
 	var lookup_offset := INST_BRR_LOOKUP + (id*3)
 	rom.seek(lookup_offset)
 	var brr_offset := read_rom_address(rom)
 	rom.seek(brr_offset)
 	var size := rom.get_16()
-	var sample := make_sample(rom, size, sample_rate)
+	var num_samples := (size/9)*16
-	#print_debug('Loaded sample instrument #%02X with lookup offset $%06X, BRR data offset $%06X and length $%04X (%f packets)' % [id, lookup_offset, brr_offset, size, size/9.0])
+	var audio := make_sample(rom, size, sample_rate)
-	return sample
+	audio.loop_mode = AudioStreamSample.LOOP_FORWARD
+	audio.loop_begin = loop_start_packet * 16  # Each 9byte packet is 16 samples
+	audio.loop_end = num_samples-1
+	print_debug('Loaded instrument #%02X with lookup offset $%06X, BRR data offset $%06X, length $%04X (%f packets, %d samples) and loop point %d samples' % [id, lookup_offset, brr_offset, size, size/9.0, num_samples, audio.loop_begin])
+	return audio
 
 func load_sfx_samples_data(rom: File):
 	var sample_rates = []
 	rom.seek(SFX_SR)
 	for i in SFX_NUM:
-		sample_rates.append((rom.get_16() * 32000)/4096)
+		var tuning1 := rom.get_8()
+		var tuning2 := rom.get_8()
+		sample_rates.append(get_reference_pitch_samplerate(tuning1))
 	var brr_spc_addrs = []
 	var brr_spc_loop_addrs = []
 	rom.seek(SFX_BRR_SPC_TABLE)
@@ -119,9 +139,9 @@ func load_sfx_samples_data(rom: File):
 		brr_spc_addrs[i] += SFX_BRR_START - brr_spc_start
 	for i in SFX_NUM:
 		rom.seek(brr_spc_addrs[i])
-		print('Loading sfx sample #%X with BRR data offset $%06X' % [i, rom.get_position()])
+		# print('Loading sfx sample #%X with BRR data offset $%06X' % [i, rom.get_position()])
 		sfx_samples.append(make_sample(rom, 900, sample_rates[i]))  # Use 900 as a limit, it won't be hit, parser stops after End packet anyway
-		print('size of %d samples' % sfx_samples[i].data.size())
+		# print('size of %d samples' % sfx_samples[i].data.size())
 
 
 # Called when the node enters the scene tree for the first time.