On Wed, 10 Dec 2003, Paul Davis wrote:

> >I wanted to check my knowledge of something: does an xrun necessarily
> >correspond to a "drop-out" in the audio stream?  In other words, could
> >you have a drop-out WITHOUT an xrun, or an xrun WITHOUT a drop-out?  Is
> >there a strict one-to-one correspondence between the two?
> 
> a dropout occurs when the h/w playback pointer gets ahead of the data
> already written by the s/w (i.e. repeating data already played). its
> therefore a 1:1 correspondence with an xrun, which is defined in the
> same way.

To be 100% correct, in the driver, there is very small window where the 
hardware might be in xrun state, but we cannot detect this situation:

        disable_interrupts();
        pos = get_current_position();
        <--- DMA transfer occured here and position (pos) was
             on last valid sample -->
        if (xrun(pos))
                do_xrun_handling();
        enable_interrupts();

                                                Jaroslav

-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs


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