Function decode_source_audio_f32 

pub fn decode_source_audio_f32(
    source: &Path,
    sample_rate: u32,
    channels: u8,
) -> Result<Vec<f32>, EncodeError>

Decode source’s audio track to interleaved F32LE samples at sample_rate / channels (ED.21). Returns an empty Vec when the source has no audio track (probed via scratch_has_audio) — the caller then exports video-only.

Errors

EncodeError::Spawn if gst-launch-1.0 isn’t on PATH; EncodeError::PipelineFailed if the decode pipeline exits non-zero.