[alsa-devel] Is there a way to figure out if the clocks of two snd_pcm_t's deviate? (snd_pcm_info_get_sync?)

Lennart Poettering mznyfn at 0pointer.de
Fri Sep 4 01:03:51 CEST 2009


I am looking for a way to find out whether the clocks of two
snd_pcm_t's are perfectly in sync and don't deviate (or only deviate
by a constant phase). 

i.e. for real duplex devices that use the same crystal for input and
output this should tell me "Yes" for the playback snd_pcm_t tested
against the recording snd_pcm_t; and for all other, unrelated audio
devices it should return "No".

I found snd_pcm_info_get_sync() in the docs, but its documentation is
a bit terse, so I am wondering if this might be what I want. Is it?

Does this (untested) code snippet do what I hope it does?

  snd_pcm_info(a, info_a);
  snd_pcm_info(b, info_b);
  in_sync = memcmp(&snd_pcm_info_get_sync(info_a), &snd_pcm_info_get_sync(info_b)) == 0;



Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

More information about the Alsa-devel mailing list