Re: return value of snd_pcm_hw_params_set_rate_near

[mru@kth.se (Måns Rullgård)]

Doug McLain <nostar@comcast.net> writes:

> According to the alsa documentation, the return value of
> snd_hw_params_set_rate_near is the 'approximate chosen rate', and the
> 3rd arg being type 'int'.  The two tutorials at the documentation
> section of the alsa-project website both hold true to this with code
> like:
>
> exact_rate = snd_pcm_hw_params_set_rate_near(pcm_handle, hwparams, rate, &dir);
>     if (dir != 0) {
>       fprintf(stderr, "The rate %d Hz is not supported by your
>       hardware.\n                      ==> Using %d Hz instead.\n",
>       rate, exact_rate);
>     }
>
> After unsuccesful attempts at using this function this way (I'm
> learning linux audio software devel starting with alsa drivers and
> user interface), I went into the aplay source and found the version
> that tests a before and after version of arg 3 (which is a pointer to
> int that gets changed to the result rate by the function) and tests
> the return only for err. I assume this function changed?  Im at the
> learning stage so I'm probably stating the obvious, but when your new
> sometimes reassurance from someone that knows helps.  Is the
> documentaion just behind, or did this slip by unnoticed?  Curious...

The function was changed some time ago, along with a few other similar
cases.

-- 
Måns Rullgård
mru@kth.se



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