[linux-audio-dev] Synchronizing two Delta 1010 with ALSA ?

Paul Davis paul at linuxaudiosystems.com
Fri Apr 11 08:08:00 UTC 2003

>I managed to write ALSA code that writes to a single card:
>it opens the PCM hw:0 device selects 10 channel interleaved S32_LE mode
>and then writes out some data. This works perfectly for a single card.

not entirely suprising: its the most basic thing to do :)

>Now my question:
>I would like to extend this app so that it writes to both cards simultaneously
>without going out of sync.

why do this again and again for every application? why not work on
alsa-lib's existing support for linked cards and make it work without
any extra snd_pcm_t's in application code? alsa-lib already supports
linking the h/w together via ~/.asoundrc, but AFAIK it doesn't attempt
to keep them in sync. working on this within alsa-lib would be much
more valuable than an app-specific solution.

>Or is some special "sync start" procedure needed ?
>I remember ALSA had/has provides some functionality in this regard
>but I was unable to find documentation about it.

snd_pcm_link() will link the two handles together. start/stop/pause
operations then work on both of them. it does not ensure sync.


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