Hi,

2011/9/27 Mike Owens <[email protected]>:
> On Tue, Sep 27, 2011 at 7:50 AM, Romain Beauxis <[email protected]>
> wrote:
>>
>> I will not start a long rant in here but I think we will probably
>> start recommending using pulseaudio for all basic input/output needs
>> in liquidsoap with the next release..
>
>
> I know I am missing something -- as the more I try to learn about Linux
> sound, the less I seem to understand it --- but ... pulseaudio ultimately
> runs on top of ALSA, right? So how does adding another layer (pulse) to
> something that is kind of a pain (ALSA) make it less painful?

Hmm.. Let me give you one example. For setting the sample rate of a
pcm device, alsa provides a function named "set_rate_near".. Near
meaning "yeah, you will get the closest value that the pcm device can
do".

Now, as explained before, if the device you're trying to use happens
to be "default", then you are fine and you will get what you asked
because alsa will do the conversion for you. However, if your user
passes "hw:0,0" you will most likely get another rate and it will be
up to the application to do something about it.

Thus, even if alsa has a standard methods to correct hardware
limitations, applications using alsa still have to deal with low-level
issues, depending on the user's request. I personally call that a
failure of the API/model.

Pulse is a uniform layer. The part of the API we use is minimal,
simple and works. Pulse also has an excellent clock mechanism with
which full-duplex works while were still trying to figure out the
correct low-level params to do it with alsa. Finally, it works on top
of alsa, oss, etc.. making it more portable for the application, which
does not have to care about the underlying driver/system.

The only case where you should use alsa if you can use pulse is when
you need low-latency input or output. Other than that, I really
recommend trying first with pulse..

> I'm all for
> whatever works. I am just trying to understand. I have run LC off of pulse
> in the past and it worked fine. But I most often run LC from Ubuntu server
> which doesn't install pulse, and setting that up can sometimes be
> challenging as well.

That I did not know.. It is rather unfortunate..

Romain

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