On Tue, 14 Jan 2003, Paul Davis wrote:
> >> that said, i think it would be great if this found its way into libasound.
> >
> >I wonder why to implement this function when one can link more pcm streams
> >with "snd_pcm_link()" together? Then polling one stream is sufficient when
> >streams are hardware synchronized.
>
> why don't you go read the function in question and then consider
> whether that would actually accomplish anything like what it does? i
> say that because i don't think its even close.
Why not? In the perfect world, when the hardware supports paralel start of
multiple streams and application sets all equal parameters for all
streams, the pointers to ring buffer are equal. Thus checking of only one
stream is quite sufficient before r/w operation.
When hardware does not support paralel start, but the parts are running at
same clock, then you can expect that last started stream in serialized
start sequence (as ALSA driver does) has valid position and all other
streams, too.
And if clock are not synced, you cannot expect nothing and your code will
fail later (when you don't do clock corrections), too.
So resume:
1) use snd_pcm_link to link all streams
2) start first linked stream (thus all in paralel or serial or combination
sequence)
3) poll the last stream handle for valid position
And you don't need your complicate function.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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