[alsa-devel] What does snd_pcm_delay() actually return?
mznyfn at 0pointer.de
Fri Jun 13 16:29:23 CEST 2008
On Fri, 13.06.08 15:55, Jaroslav Kysela (perex at perex.cz) wrote:
> On Fri, 13 Jun 2008, Lennart Poettering wrote:
> > c) snd_pcm_hw_params_get_buffer_size() - snd_pcm_update_avail()
> > returns the fill level, but only works on mmap.
> snd_pcm_update_avail() works (or should work) also for standard r/w
Ok, so it's just the documentation that needs fixing? Quoting: "Using
of this function is useless for the standard read/write
operations. Use it only for mmap access."
> > d) The snd_pcm_hw_params_get_fifo_size() was supposed to return the
> > 'difference' between a) and c), but was never actually used
> > for that.
> Nope. It's maximum latency added by an extra fifo/queue (it does not
> depend if it's hw or sw fifo). For variable fifo size, we need to extend
Ok, so it's an upper ceiling for the difference between a) and c), right?
Lennart Poettering Red Hat, Inc.
lennart [at] poettering [dot] net ICQ# 11060553
http://0pointer.net/lennart/ GnuPG 0x1A015CC4
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