def infer_channels_from_layout(layout, channels):
    """Extract the number of channels from the layout."""
    if layout in ("TBD", "BTD"):
        if channels is not None and channels != 1:
            raise ValueError(
                "Expected channels ({}) to be 1 for layout = {}".format(
                    channels, layout
                )
            )
        if channels is None:
            return 1
    return channels
Extract the number of channels from the layout.
fairseq/models/speech_to_text/utils.py