[alsa-devel] Hidden rate conversion, and Alsa configuration

James Courtier-Dutton James at superbug.co.uk
Fri Aug 3 16:29:48 CEST 2007

Alan Horstmann wrote:
> On Friday 27 July 2007 21:16, Jaroslav Kysela wrote:
>> On Fri, 27 Jul 2007, stan wrote:
>>> I really want to avoid rate resampling if I can, while format
>>> conversion has to occur somewhere in order to match the hardware in
>>> most cases.  I assume that any format conversion alsa does
>>> is at least as good as one I would do myself.  While the rate
>> I answered this numerous times on this list. We have a function to notify
>> the plugins that resampling should be avoided - it's
>> snd_pcm_hw_params_set_rate_resample().
> Can this function be built into an ALSA configuration file in some way, or can 
> it only be called from an app?
> Alan
It is only really sensible to have the app do the call, and not a config 
Reason being, if the app does the call, it must also be able to handle 
the resampling itself.
If the config file did it, the app might not be able to do the 
resampling itself and therefore fail to play anything.
Generally, the app is the best place to do the resampling, as it can 
handle the quality issues better.
The resampler in ALSA is only really there to let other apps that don't 
do resampling limp along ok.


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