HAL headroom question
HAL headroom question
- Subject: HAL headroom question
- From: Kurt Bigler <email@hidden>
- Date: Wed, 06 Mar 2002 17:35:17 -0800
In chapter 2 (HAL) on page 16, coreaudio.pdf says:
>
Note that if an Audio Stream presents its format as linear PCM, it will always
>
present its data as 32-bit floating point data. Any necessary conversion to
>
the actual physical hardware format (such as 16 or 24 bit integer) are handled
>
by the driver in order to preserve the headroom of the device9s mix bus.
>
>
The format-related properties of Audio Devices simply vector the request to
>
the stream containing the requested channel and direction.
>
>
An Audio Device should support an arbitrary number of clients, although it is
>
not required to.
The presence of the word "headroom" makes me wonder how the amplitudes seen
by an application relate to the amplitudes seen by the hardware, given the
multiple-client scenario.
Is it possible that an application's output to a device might be attenuated
due to multi-client mixing rather than simply clipped? If not, what is the
"headroom" about?
Thanks,
Kurt Bigler
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