[Haskell-cafe] FFI woes!
sebastian.sylvan at gmail.com
Fri Dec 17 18:55:27 EST 2004
On Thu, 16 Dec 2004 18:20:52 +0000, Keean Schupke
<k.schupke at imperial.ac.uk> wrote:
> In which case I would assume the whole sample is copied to the sound
> cards buffer
> before the play call returns, so you don't have to worry and just let it
> be garbage collected.
What do you mean?
Yes the sample is copied to memory when loaded, but I still have to
"worry" because if it's garbage colleced (ie, a "free" call is called
on it) then the sound can not be played anymore (because the data is
> Sebastian Sylvan wrote:
> >On Thu, 16 Dec 2004 12:35:55 +0000, Keean Schupke
> ><k.schupke at imperial.ac.uk> wrote:
> >>Okay, you want to poll to see if the sound is still playing... This is
> >>not very
> >>easy to do...
> >>You really want to use the low-buffer callback from the soundcard
> >>driver to load the next sample into the buffer using DMA. (IE you
> >>can pass a function to the driver to call when you sample has been
> >>copied completely to the sound-cards memory). This is the way to
> >>do it...
> >> play_then_free = do
> >> set_callback (free_sample my_sample)
> >> play_sample my_sample
> >>You can see that this provides the interface you want to the user (IE
> >>samples are freed once they are finished with)...
> >> Keean.
> >This is exactly how I do it for the Stream sound type, since this type
> >of sound supplies a callback for when it reaches the end. The sound
> >sample does not, though.
> >(stream is streamed from disk, sound sample is loaded into memory).
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