fix(switch): widen Pikachu PCM to 16-bit stereo without Source channel probe

Source:getChannelCount could skip the #626 widen on love-nx, and keeping
8-bit depth into a stereo buffer still sounded wrong on audren. Decode the
file via newSoundData, always emit 16-bit stereo like ChipSynth, and write
fresh pika-cry WAVs as stereo at extract time so re-imports skip the hop.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/core/Sound.lua

@@ -92,19 +92,30 @@ end
 -- Chip SFX and cries are already stereo at the source (ChipSynth
 -- renderEffectData); this covers file defs, i.e. Yellow's 8-bit mono PCM
 -- Pikachu clips (RomExtractor extractPikachuCries) and mod-supplied wav/ogg
--- SFX.  Every step is guarded: a headless love stub without love.sound, or a
--- decoder that will not hand back SoundData, keeps the original Source.
+-- SFX.
+--
+-- Decode the FILE (not Source:getChannelCount): love-nx/audren has reported
+-- channel counts that skip this widen silently, and preserving 8-bit depth
+-- into a stereo buffer also sounds wrong on that backend.  Always emit
+-- 16-bit stereo like ChipSynth.  Failure keeps the original Source and logs.
 local function widenMono(source, file)
-  if not (source and love.sound and love.sound.newSoundData) then
+  if type(file) ~= "string" then return source end
+  if not (love.sound and love.sound.newSoundData and love.audio
+      and love.audio.newSource) then
+    return source
+  end
+  -- Quiet skip when the path is unreadable (headless stub SFX keys, missing
+  -- files).  On NX, overlay-wrapped getInfo makes the yellow|blue copy visible
+  -- at the bare assets/generated path so the widen still runs.
+  local fs = love.filesystem
+  if not (fs and fs.getInfo and fs.getInfo(file)) then
     return source
   end
-  local ok, channels = pcall(function() return source:getChannelCount() end)
-  if not ok or channels ~= 1 then return source end
   local built, widened = pcall(function()
     local mono = love.sound.newSoundData(file)
+    if mono:getChannelCount() ~= 1 then return source end
     local frames = mono:getSampleCount()
-    local stereo = love.sound.newSoundData(frames, mono:getSampleRate(),
-                                           mono:getBitDepth(), 2)
+    local stereo = love.sound.newSoundData(frames, mono:getSampleRate(), 16, 2)
     for index = 0, frames - 1 do
       local value = mono:getSample(index)
       stereo:setSample(index, 1, value)
@@ -112,7 +123,10 @@ local function widenMono(source, file)
     end
     return love.audio.newSource(stereo, "static")
   end)
-  if built and widened then return widened end
+  if built and widened and widened ~= source then return widened end
+  if not built then
+    Logger.warn("sound: widenMono failed for %s: %s", file, tostring(widened))
+  end
   return source
 end
 
@@ -274,9 +288,9 @@ function Sound.playPikaCry(data, n)
       cache[key] = false
       return nil
     end
-    -- the importer writes these clips as 8-bit mono (RomExtractor
-    -- extractPikachuCries), so they need the same widening as the chip
-    -- effects to stay off a multi-output device's surround channels (#626)
+    -- importer historically wrote these as 8-bit mono (RomExtractor
+    -- extractPikachuCries); widenMono re-decodes to 16-bit stereo so they
+    -- stay off surround outputs (#626).  Fresh extracts are already stereo.
     s = widenMono(s, path)
     s:setVolume(volumeFor(key))
     cache[key] = s

src/import/RomExtractor.lua

@@ -2023,21 +2023,23 @@ end
 -- PikachuCriesPointerTable, 42 `dba` rows; each clip is `dw length` then
 -- 1-bit PCM, MSB first -- home/pikachu_cries.asm PlayPikachuPCM toggles
 -- rAUD3LEVEL per bit at roughly 190 CPU cycles a sample).  Decoded to
--- plain 8-bit mono WAVs; returns the clip count for data.audio.pikaCries,
+-- 16-bit stereo WAVs (identical L/R) so OpenAL never spatializes them as
+-- ambient surround (#626); returns the clip count for data.audio.pikaCries,
 -- or nil when the manifest has no pointer table (Red/Blue).
 function RomExtractor:extractPikachuCries()
   if not self.symbols["PikachuCriesPointerTable"] then return nil end
   local NUM = 42   -- NUM_PIKA_CRIES
   local RATE = 22050 -- ~4.19 MHz / ~190 cycles per sample
-  -- byte -> 8 samples, MSB first (LoadNextSoundClipSample: `and $80`)
+  -- byte -> 8 mono sample levels, MSB first (LoadNextSoundClipSample: `and $80`)
+  -- levels match the old unsigned-8 WAV (on=0xE0, off=0x20) as floats in [-1,1]
   local lut = {}
   for byte = 0, 255 do
     local out = {}
     for bit = 7, 0, -1 do
       local on = math.floor(byte / 2 ^ bit) % 2 == 1
-      out[#out + 1] = string.char(on and 0xE0 or 0x20)
+      out[#out + 1] = on and ((0xE0 - 128) / 128) or ((0x20 - 128) / 128)
     end
-    lut[byte] = table.concat(out)
+    lut[byte] = out
   end
   local function u16(v)
     return string.char(v % 256, math.floor(v / 256) % 256)
@@ -2046,6 +2048,12 @@ function RomExtractor:extractPikachuCries()
     return string.char(v % 256, math.floor(v / 256) % 256,
       math.floor(v / 65536) % 256, math.floor(v / 16777216) % 256)
   end
+  local function i16le(f)
+    local v = math.floor(f * 32767 + (f >= 0 and 0.5 or -0.5))
+    if v > 32767 then v = 32767 elseif v < -32768 then v = -32768 end
+    if v < 0 then v = v + 65536 end
+    return string.char(v % 256, math.floor(v / 256) % 256)
+  end
   local CacheFs = require("src.import.CacheFs")
   local pointers = self:symbol("PikachuCriesPointerTable")
   for index = 0, NUM - 1 do
@@ -2054,11 +2062,16 @@ function RomExtractor:extractPikachuCries()
     local header = self.rom:bytes(bank, address, 2)
     local length = header[1] + header[2] * 256
     local raw = self.rom:bytes(bank, address + 2, length)
-    local samples = {}
-    for i, byte in ipairs(raw) do samples[i] = lut[byte] end
-    local pcm = table.concat(samples)
+    local parts = {}
+    for _, byte in ipairs(raw) do
+      for _, level in ipairs(lut[byte]) do
+        local s = i16le(level)
+        parts[#parts + 1] = s .. s -- identical L/R (#626)
+      end
+    end
+    local pcm = table.concat(parts)
     local wav = "RIFF" .. u32(36 + #pcm) .. "WAVEfmt " .. u32(16)
-      .. u16(1) .. u16(1) .. u32(RATE) .. u32(RATE) .. u16(1) .. u16(8)
+      .. u16(1) .. u16(2) .. u32(RATE) .. u32(RATE * 4) .. u16(4) .. u16(16)
       .. "data" .. u32(#pcm) .. pcm
     local ok, err = CacheFs.write(
       ("assets/generated/audio/pika_cries/cry_%02d.wav"):format(index + 1),

tests/engine/assets_version_fallback_test.lua

@@ -74,8 +74,11 @@ eq(type(chunk) == "function" and chunk() or nil, 42,
   "wrapped filesystem.load resolves the versioned chunk")
 
 local sd = love.sound.newSoundData(PNG)
-eq(sd.samples, "yellow/" .. PNG,
+eq(sd.path, "yellow/" .. PNG,
   "wrapped newSoundData receives the yellow/ path (widenMono's re-read)")
+eq(sd:getChannelCount(), 1,
+  "path-form newSoundData stays mono so widenMono has work to do")
+eq(sd:getBitDepth(), 8, "path-form stub mimics the 8-bit pika-cry WAVs")
 
 local fnt = love.graphics.newFont(14)
 check(fnt ~= nil, "wrapped newFont ignores non-path arguments")

tests/engine/nx_yellow_boot_test.lua

@@ -92,15 +92,18 @@ function Source:play() self.playing = true end
 function Source:stop() self.playing = false end
 function Source:setVolume() end
 function Source:isPlaying() return self.playing end
--- Mono so Sound.widenMono actually reaches newSoundData (the stub's path
--- form then fails inside the pcall and widenMono keeps this Source --
--- enough to prove the overlay rewrote the re-read path).
-function Source:getChannelCount() return 1 end
+function Source:getChannelCount() return self.channels or 1 end
 
 love.audio = {
-  newSource = function(path, mode)
-    record("source", path)
-    return setmetatable({ path = path, mode = mode }, Source)
+  newSource = function(pathOrData, mode)
+    record("source", pathOrData)
+    local channels = 1
+    if type(pathOrData) == "table" and pathOrData.getChannelCount then
+      channels = pathOrData:getChannelCount()
+    end
+    return setmetatable({
+      path = pathOrData, mode = mode, channels = channels,
+    }, Source)
   end,
 }
 
@@ -227,20 +230,26 @@ eq(pre and pre.nidoFrames and pre.nidoFrames[3]
 
 -- Yellow's voiced Pikachu clip: a FORMATTED path (cry_%02d.wav), invisible
 -- to the static guard.  playPikaCry also runs widenMono, which re-reads the
--- same bare path via newSoundData -- that second hop is what the full-surface
--- overlay exists to cover.
+-- same bare path via newSoundData and must emit a 16-bit STEREO Source
+-- (#626) -- path rewrite alone is not enough on Switch audren.
 local cry = Sound.playPikaCry({ audio = { pikaCries = 1 } }, 1)
 check(cry ~= nil, "playPikaCry returns a source on NX Yellow")
-eq(cry and cry.path, "yellow/assets/generated/audio/pika_cries/cry_01.wav",
-  "the formatted pika-cry path resolves to the yellow/ copy")
+eq(cry and cry:getChannelCount(), 2,
+  "playPikaCry widens the mono PCM clip to stereo")
 local sawCrySoundData = false
+local sawCrySource = false
 for _, r in ipairs(recorded) do
   if r.kind == "sounddata"
       and r.path == "yellow/assets/generated/audio/pika_cries/cry_01.wav" then
     sawCrySoundData = true
-    break
+  end
+  if r.kind == "source"
+      and r.path == "yellow/assets/generated/audio/pika_cries/cry_01.wav" then
+    sawCrySource = true
   end
 end
+check(sawCrySource,
+  "newSource loaded the cry through the yellow/ prefix")
 check(sawCrySoundData,
   "widenMono re-read the cry via newSoundData with the yellow/ path")
 

tests/love_stub.lua

@@ -278,6 +278,25 @@ function SoundData:getDuration() return self.samples / self.rate end
 
 stub.sound = {
   newSoundData = function(samples, rate, bits, channels)
+    -- Path form (love.sound.newSoundData(filename)): only succeed when the
+    -- stub FS has the file, matching real LÖVE.  Synthesize a short mono
+    -- 8-bit buffer so Sound.widenMono can run headless for seeded paths
+    -- (pika cries); missing files must error so widenMono keeps the
+    -- original Source (give_item_jingle identity checks, etc.).
+    if type(samples) == "string" then
+      if not stub.filesystem.getInfo(samples) then
+        error("Could not open file " .. samples .. ". Does not exist.")
+      end
+      local n = 32
+      local sd = setmetatable({
+        samples = n, rate = rate or 22050, bits = bits or 8,
+        channels = channels or 1, data = {}, path = samples,
+      }, SoundData)
+      for i = 0, n - 1 do
+        sd:setSample(i, (i % 2 == 0) and 0.5 or -0.5)
+      end
+      return sd
+    end
     return setmetatable({ samples = samples, rate = rate or 44100,
       bits = bits or 16, channels = channels or 1, data = {} }, SoundData)
   end,