Re: pointer callback in pcm

[Adrian McMenamin <adrian@mcmen.demon.co.uk>]

On Thu, 2006-03-09 at 19:53 -0500, Lee Revell wrote:
> On Thu, 2006-03-09 at 22:21 +0000, Adrian McMenamin wrote:
> > The documentation states:
> > 
> > "This callback is called when the PCM middle layer inquires the current
> > hardware position on the buffer."
> > 
> > 
> > Does that mean the position the hardware is at (in its ring buffer in my
> > case) or does it mean the position we are at in the dma buffer.
> > 
> > ie I have a 128k DMA buffer which transfers samples into the 32k
> > hardware memory buffer. Which position am I meant to be reporting?
> > 
> 
> The DMA buffer should be the same size as the hardware buffer, so the
> positions should be the same.
> 
> The pointer callback should return the position of sample that the
> hardware is currently playing.
> 
Thanks. I am sure I am driving you round the twist now, but that (both
buffers being the same size) was a key piece of information I was
unaware of. There are several pints in it if you are ever around in
North London :)

But my basic problem remains - my buffer is 8 periods long and I get to
hear them over and over again :( - nothing new is ever fed into the DMA
buffer and so nothing new therefore ever gets fed into the hardware
buffer.

I start the process by transferring a whole eight periods worth into the
hardware buffer is that a mistake? Should I always be feeding in one
period at a time only?



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