PCM For ComputerCraft

local speaker = peripheral.find("speaker")
if not speaker then
    print("No speaker attached!")
    return
end

-- Prompt for filename
write("Enter PCM filename: ")
local filename = read()

-- Ask if file is signed or unsigned
write("Is your file unsigned 8-bit PCM? (y/n): ")
local isUnsigned = read():lower() == "y"

-- Prompt for input sample rate
write("Enter input sample rate (Hz, e.g. 44100): ")
local inputSampleRate = tonumber(read())
if not inputSampleRate or inputSampleRate < 1000 or inputSampleRate > 192000 then
    print("Invalid sample rate. Using 44100 Hz.")
    inputSampleRate = 44100
end

-- Prompt for volume (0.0 to 1.0)
write("Enter playback volume (0.0 - 1.0, default 0.2): ")
local volInput = read()
local volume = tonumber(volInput)
if not volume or volume < 0 or volume > 1 then
    volume = 0.2 -- default safe volume
end

-- Optional: DC offset removal
write("Remove DC offset? (y/n, default n): ")
local dcInput = read()
local removeDC = dcInput:lower() == "y"

-- Open file in binary mode
local file = fs.open(filename, "rb")
if not file then
    print("Could not open file: " .. filename)
    return
end

-- Read all samples into memory (for resampling)
local samples = {}
local sum = 0
local count = 0

while true do
    local byte = file.read()
    if not byte then break end
    if isUnsigned then
        byte = byte - 128 -- Convert unsigned (0-255) to signed (-128 to 127)
    end
    samples[#samples + 1] = byte
    sum = sum + byte
    count = count + 1
end
file.close()

if #samples == 0 then
    print("File is empty or unreadable.")
    return
end

-- Remove DC offset if requested
if removeDC then
    local avg = sum / count
    for i = 1, #samples do
        samples[i] = samples[i] - avg
    end
    print("DC offset removed (average sample value: " .. math.floor(avg) .. ")")
end

-- Resample to 48000 Hz (CraftOS-PC speaker expects 48kHz 8-bit signed PCM)
local outputSampleRate = 48000
if inputSampleRate ~= outputSampleRate then
    local resampled = {}
    local ratio = inputSampleRate / outputSampleRate
    for i = 1, math.floor(#samples / ratio) do
        -- Linear interpolation for smoother sound
        local src = (i - 1) * ratio + 1
        local idx = math.floor(src)
        local frac = src - idx
        local s1 = samples[idx] or 0
        local s2 = samples[idx + 1] or s1
        resampled[i] = s1 + (s2 - s1) * frac
    end
    samples = resampled
    print("Resampled to 48kHz for optimal playback.")
end

-- Chunked playback with volume scaling and clamping
local chunkSize = 128 * 1024  -- Max buffer size per playAudio call
local totalSamples = #samples
local playedSamples = 0

while playedSamples < totalSamples do
    local chunk = {}
    for i = 1, chunkSize do
        local idx = playedSamples + i
        if idx > totalSamples then break end
        -- Volume scaling and clamping
        local sample = math.floor(samples[idx] * volume + 0.5)
        if sample > 127 then sample = 127 end
        if sample < -128 then sample = -128 end
        chunk[i] = sample
    end
    if #chunk == 0 then break end
    while not speaker.playAudio(chunk) do
        os.pullEvent("speaker_audio_empty")
    end
    playedSamples = playedSamples + #chunk
end

print("Done playing " .. filename)