[alsa-devel] ALSA: Updating Sample Rates in sound/core/pcm_native.c

Takashi Iwai tiwai at suse.de
Thu Apr 19 08:02:28 CEST 2012

At Wed, 18 Apr 2012 19:51:18 -0400,
Jeremy Torres wrote:
> Hello,
> I have updated pcm.h in the linux kernel to allow for new sample
> rates.

No, don't do that unless rates are commonly used by many drivers.
Use snd_pcm_hw_constraint_list() instead.

>  For example, I have added 128000 and 144000 sample rates.  Per
> the documentation in pcm.h, I also updated pcm_native.c (the rates
> table).  However when I try and use the "default" device for the
> sample rates:
> 1.  For 128000: plug conversion occurs for 128K, but the slave is
> configured to 96K;
> 2.  For 144000: plug conversion is attempted at the 176400 rate;

If the problem still happens even with the explicit rate list,
it's easier to debug when you give the patch.


> Note that:
> a) I have snd_pcm_hw_resample set to FALSE in my application; however,
> I've been using aplay/arecord to test as well with repeatable results.
> b) I do not have an asoundrc setup for plug conversion, etc.  I only
> have the default /usr/share/alsa/alsa.conf;
> c) When I try the the device "hw:0,0", I get a (proper) warning that
> the sample rate requested is not being honored (i.e., 96K instead of
> 128K).
> I have placed debug in pcm_lib.c,  and pcm_native.c and my sample rate
> constraints are set.  My understanding is if I define a specific rate
> and it can be matched in the "rates" table, it should be honored.
> Environment Info:
> ALSA lib/driver version 1.0.20
> SOC Driver
> Any help would be greatly appreciated!
> Regards,
> Jeremy
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