# `WhisperCt2.Pcm`
[🔗](https://github.com/rubas/whisper_ct2/blob/v0.5.0/lib/whisper_ct2/pcm.ex#L1)

Helpers for slicing little-endian f32 PCM buffers without re-decoding the
source audio.

A diarization-driven workflow typically decodes the master audio to
f32 PCM once (upstream of this library) and then runs many short
transcribe calls over per-turn slices. `slice/4` does the byte math
(4 bytes per sample at `sample_rate` samples/second) and bounds-checks
against the buffer size.

# `slice`

```elixir
@spec slice(binary(), pos_integer(), number(), number()) ::
  {:ok, binary()} | {:error, WhisperCt2.Error.t()}
```

Returns the f32-PCM bytes for `[start_s, start_s + duration_s)`.

`samples` is a binary of little-endian `f32` samples at `sample_rate`
samples/second. Both `start_s` and `duration_s` are seconds; either
integer or float.

Returns `{:error, %WhisperCt2.Error{reason: :invalid_request}}` when:

- `start_s < 0`;
- `duration_s` is zero or negative, or rounds to zero samples;
- the requested window is not fully contained in the buffer
  (`start_sample + requested_samples > total_samples`).

The range is **not** clamped — slicing past the end is a caller bug
and we surface it loudly. Bound your duration before calling, or use
`min(duration_s, buffer_duration - start_s)`.

---

*Consult [api-reference.md](api-reference.md) for complete listing*