Correct frequency shifts on wave channel

This mirrors the tone channels as far as implementation, and corrects
an issue where the sample buffer was getting misaligned on frequency
updates that didn't start new notes.

gameboy/audio.lua

@@ -53,7 +53,7 @@ audio.reset = function()
   audio.tone2.frequency_last_update = 0 -- in cycles
   audio.tone2.period_counter = 0
   audio.tone2.wave_duty_counter = 0
-  audio.tone1.frequency_shadow = 0
+  audio.tone2.frequency_shadow = 0
 
   audio.wave3.debug_disabled = false
   audio.wave3.enabled = false
@@ -62,6 +62,10 @@ audio.reset = function()
   audio.wave3.period = 0 -- in cycles
   audio.wave3.continuous = false
   audio.wave3.base_cycle = 0
+  audio.wave3.frequency_last_update = 0 -- in cycles
+  audio.wave3.period_counter = 0
+  audio.wave3.sample_index = 0
+  audio.wave3.frequency_shadow = 0
 
   audio.noise4.debug_disabled = false
   audio.noise4.volume_initial = 0
@@ -289,9 +293,12 @@ io.write_logic[ports.NR34] = function(byte)
   local freq_value = freq_high + freq_low
 
   audio.wave3.period = 64 * (2048 - freq_value)
+  audio.wave3.period_conter = (2048 - freq_value)
+  audio.wave3.frequency_shadow = freq_value
   audio.wave3.continuous = continuous
   if restart then
     audio.wave3.base_cycle = timers.system_clock
+    audio.wave3.sample_index = 0
   end
 end
 
@@ -475,17 +482,26 @@ audio.wave3.generate_sample = function(clock_cycle)
   local duration = clock_cycle - wave3.base_cycle
   if wave3.enabled then
     if wave3.continuous or (duration <= wave3.max_length) then
-      local period = wave3.period
-      local period_progress = (duration % period) / (period)
-      local sample_index = math.floor(period_progress * 32)
-      if sample_index > 31 then
-        sample_index = 31
+      --local period = wave3.period
+      --local period_progress = (duration % period) / (period)
+      --local sample_index = math.floor(period_progress * 32)
+      while clock_cycle > wave3.frequency_last_update + 2 do
+        wave3.period_counter = wave3.period_counter - 1
+        if wave3.period_counter <= 0 then
+          wave3.period_counter = (2048 - wave3.frequency_shadow)
+          wave3.sample_index = wave3.sample_index + 1
+          if wave3.sample_index >= 32 then
+            wave3.sample_index = 0
+          end
+        end
+        wave3.frequency_last_update = wave3.frequency_last_update + 2
       end
-      local byte_index = bit32.rshift(sample_index, 1)
+
+      local byte_index = bit32.rshift(wave3.sample_index, 1)
       local sample = io.ram[0x30 + byte_index]
       -- If this is an even numbered sample, shift the high nybble
       -- to the lower nybble
-      if sample_index % 2 == 0 then
+      if wave3.sample_index % 2 == 0 then
         sample = bit32.rshift(sample, 4)
       end
       -- Regardless, mask out the lower nybble; this becomes our sample to play

love/main.lua

@@ -118,6 +118,23 @@ function play_gameboy_audio(buffer)
   love.audio.play(source)
 end
 
+function dump_audio(buffer)
+  -- play the sound still
+  play_gameboy_audio(buffer)
+  -- convert this to a bytestring for output
+  local output = ""
+  local chars = {}
+  for i = 0, 32768 - 1 do
+    local sample = buffer[i]
+    sample = math.floor(sample * (32768 - 1)) -- re-root in 16-bit range
+    chars[i * 2] = string.char(bit32.band(sample, 0xFF))
+    chars[i * 2 + 1] = string.char(bit32.rshift(bit32.band(sample, 0xFF00), 8))
+  end
+  output = table.concat(chars)
+
+  love.filesystem.append("audiodump.raw", output, 32768 * 2)
+end
+
 function love.load(args)
   sound_buffer = love.sound.newSoundData(32768, 32768, 16, 2)
   love.graphics.setDefaultFilter("nearest", "nearest")
@@ -169,9 +186,7 @@ function love.load(args)
   window_title = "LuaGB - " .. gameboy.cartridge.header.title
   love.window.setTitle(window_title)
 
-  gameboy.audio.on_buffer_full(function(buffer)
-    play_gameboy_audio(buffer)
-  end)
+  gameboy.audio.on_buffer_full(play_gameboy_audio)
 
   love.audio.setVolume(0.1)
 end
@@ -270,6 +285,20 @@ action_keys.kp3 = function() toggle_panel("oam") end
 action_keys.kp4 = function() toggle_panel("disassembler") end
 action_keys.kp5 = function() toggle_panel("audio") end
 
+local audio_dump_running = false
+action_keys.a = function()
+  if audio_dump_running then
+    gameboy.audio.on_buffer_full(play_gameboy_audio)
+    print("Stopped dumping audio.")
+    audio_dump_running = false
+  else
+    love.filesystem.remove("audiodump.raw")
+    gameboy.audio.on_buffer_full(dump_audio)
+    print("Started dumping audio to audiodump.raw ...")
+    audio_dump_running = true
+  end
+end
+
 action_keys.lshift = function() profile_enabled = not profile_enabled end
 
 local input_mappings = {}