What causes "PCM16 input must contain complete 16-bit samples." in moeru-ai/airi?

Verify pcmBytes.byteLength % 2 === 0 before calling; if odd, buffer the trailing byte and prepend it to the next chunk.

moeru-ai/airi · error · TypeError

PCM16 input must contain complete 16-bit samples.

Error message

PCM16 input must contain complete 16-bit samples.

What it means

Thrown by toFloat32FromPCM16 when the byte length of the PCM byte array is not an even multiple of 2 (Int16Array.BYTES_PER_ELEMENT). Every 16-bit PCM sample occupies exactly two little-endian bytes, so an odd-length buffer cannot represent complete samples and conversion is refused rather than silently dropping or misreading a byte.

Source

Thrown at packages/audio/src/encoding/wav.ts:65

  for (let i = 0; i < samples.length; i++) {
    const sample = Math.max(-1, Math.min(1, samples[i]))
    const value = sample < 0 ? sample * 0x8000 : sample * 0x7FFF
    dataView.setInt16(i * Int16Array.BYTES_PER_ELEMENT, value, true)
  }

  return output
}

/**
 * Converts little-endian signed PCM16 bytes to normalized Float32 PCM samples.
 *
 * @example
 * toFloat32FromPCM16(new Uint8Array([0, 128, 0, 0, 255, 127]))
 * // => Float32Array([-1, 0, 0.999969482421875])
 */
export function toFloat32FromPCM16(pcmBytes: Uint8Array): Float32Array<ArrayBuffer> {
  if (pcmBytes.byteLength % Int16Array.BYTES_PER_ELEMENT !== 0)
    throw new TypeError('PCM16 input must contain complete 16-bit samples.')

  const dataView = new DataView(pcmBytes.buffer, pcmBytes.byteOffset, pcmBytes.byteLength)
  const output = new Float32Array(pcmBytes.byteLength / Int16Array.BYTES_PER_ELEMENT)

  for (let i = 0; i < output.length; i++)
    output[i] = dataView.getInt16(i * Int16Array.BYTES_PER_ELEMENT, true) / 0x8000

  return output
}

/**
 * Encodes Float32 samples as a WAV file.
 *
 * @example
 * toWav(float32Samples.buffer, 24000)
 * // => WAV data with converted PCM16 samples
 */
export function toWav(buffer: ArrayBufferLike, sampleRate: number, channel = 1): ArrayBuffer {

View on GitHub (pinned to 0616eabd5b)

Solutions

Verify pcmBytes.byteLength % 2 === 0 before calling; if odd, buffer the trailing byte and prepend it to the next chunk.
If chunking, accumulate bytes and only convert on even boundaries (carry over the leftover byte).
Check the upstream producer/transport (base64 decode, WebSocket frame, file slice) for truncation or off-by-one slicing.
Confirm the source audio is actually 16-bit PCM, not 8-bit or 24-bit.

Example fix

// before
const floats = toFloat32FromPCM16(chunk) // throws on odd chunk

// after
if (chunk.byteLength % 2 !== 0) {
  pending = concat(pending ?? [], chunk)
  chunk = new Uint8Array(0)
}
const floats = toFloat32FromPCM16(chunk)

Defensive patterns

Strategy: validation

Validate before calling

if (pcmBytes.byteLength % Int16Array.BYTES_PER_ELEMENT !== 0) {
  // buffer the tail byte and wait for more data, or reject the chunk upstream
  throw new Error(`Incomplete PCM16 frame: ${pcmBytes.byteLength} bytes`)
}
const floats = toFloat32FromPCM16(pcmBytes)

Type guard

function hasCompletePCM16Frames(bytes: Uint8Array): boolean {
  return bytes.byteLength % Int16Array.BYTES_PER_ELEMENT === 0
}

Try / catch

try {
  features = base64ToFeatures(b64)
} catch (err) {
  if (err instanceof TypeError && err.message.includes('complete 16-bit samples')) {
    // drop/repair the truncated payload rather than crashing the stream
  } else throw err
}

Prevention

Accumulate stream chunks in a queue and drain only even byte counts, carrying over leftover bytes.
Validate payload length at the transport boundary (base64 length, WebSocket frame size) before decoding.
Write a unit test with odd-length inputs to lock in the buffering behavior.

When it happens

Trigger: Calling toFloat32FromPCM16 (directly, or via pumpPcm16Input / base64ToFeatures) with a Uint8Array whose byteLength % 2 !== 0. Common with chunked stream reads that split a frame across chunks, or a base64 payload that was truncated by one byte.

Common situations: Audio capture callbacks delivering arbitrary byte counts; WebSocket/base64 transfer truncating payloads; slicing a buffer with a wrong offset/length; feeding 8-bit or 24-bit PCM into a PCM16 decoder; reinterpreting a subarray with a misaligned byteOffset.

Related errors

AI-assisted analysis of moeru-ai/airi@0616eabd5b (2026-08-28). Data as JSON: /api/errors/3b2854b8daf785a3. Report an issue: GitHub.