What happens upon mmdevapi capture overrun on native?

Joerg-Cyril.Hoehle at t-systems.com Joerg-Cyril.Hoehle at t-systems.com
Fri Mar 9 10:46:57 CST 2012


Maarten Lankhorst wrote in winepulse: Add pulseaudio driver, v9:
>- Reworked capture logic to always capture, since that seems to be the case on windows,
>  when stopped we simply drop whole packets, but keep firing the event.

Does anybody know what precisely happens upon overrun during capture?

A. mmdevapi fills the whole buffer once.  It keeps firing events and
   sets the DISCONTINUITY flag upon the next CaptureClient_GetBuffer.
   This is like mciwave's "record from 0 to 5000" command.
   The client can read the oldest recorded samples.

B. mmdevapi continuously overwrites the circular buffer.  It keeps
   firing events and sets the DISCONTINUITY flag too.  The client gets
   to see the newest recorded samples.  It's like your TV recorder's time
   shift function that can only travel back by as much as the buffer holds.

C. Other, e.g. mixing newest with older packets (current winealsa).

In other words, what data does the dlls/mmdevapi/capture test see in:

I think A makes sense but really I don't know.  The tests show a
position jump by one period worth of frames when reading the next
packet after an overrun.  That's not what I'd expect from behaviour A.
But from behaviour B I'd expect a much larger position jump, as large
as elapsed time.

We really need somebody with a microphone and Vista/w2k8/w7 to tell us what happens.

Does anybody know what DSound does in such a case? (not that it matters...)

Thank you,
      Jörg Höhle

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