[LAU] can jackd or ardour be forced to use interleaved mode?

Paul Davis paul at linuxaudiosystems.com
Sat May 15 18:26:21 CEST 2021

On Sat, May 15, 2021 at 7:24 AM Fons Adriaensen <fons at linuxaudio.org> wrote:

> On Sat, May 15, 2021 at 06:49:28AM -0600, Paul Davis wrote:
> > Also, at that time, ALSA didn't yet properly support the mmap'ed mode ...
> > it was under development but not finished (as evidenced by the way it
> could
> > not handle non-interleaved devices like the RME digi series.
> That's another thing that puzzles me...
> At the time audio cards like the RMEs would be sitting on a PCI bus,
> and the mmap area could/would be actual hardware buffers.
> So then, mmapped mode would be the 'natural' way, with read()/write()
> being implemented on top of it. But apparently it was the other way
> around...

That's what was changing in the late 1990s. Before "DMA-capable" audio
interfaces, you needed special data transfer operations to get data to/from
the audio interface. By 2000-2002, that mostly went away, and they were all
DMA capable. ALSA evolved to accommodate this, but there had been no reason
to focus on mmap-style access before then.
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