[alsa-devel] What does snd_pcm_delay() actually return?

Jaroslav Kysela perex at perex.cz
Fri Jun 13 15:55:56 CEST 2008

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 ops.

> 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 


Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

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