Is calling snd_pcm_sw_params() mandatory ?

Is calling snd_pcm_sw_params() mandatory ?

[Raymond Yau]

>>Twas brillig, and Raymond Yau at 24/07/10 04:51 did gyre and gimble:
>> 2010/7/15 Colin Guthrie <gmane <at> colin.guthr.ie>
>>
>>
>> Can I remove pulseaudio from mandriva 2000 ?
>>
>> I just want to test *libcanberra*-alsa alone ( i.e. *libcanberra* without
>> pulseaudio )
>>
>> when PA server abort, and *libcanberra*-pulse cannot connect to PA server ,
>>
>> Will *libcanberra* use *libcanberra*-alsa connect to PA using alsa-pulse plugin
>> ?

> Use draksound (or via Mandriva Control Center) to disable pulseaudio and
> the ALSA backend for canberra should be used instead.

> It's based on the alternatives system and the file
> /etc/sound/profiles/alsa/canberra.conf

> Col

It is strange that the alsa back end of libcanberra
(http://git.0pointer.de/?p=libcanberra.git;a=blob;f=src/alsa.c) does
not call snd_pcm_sw_params()

Does alsa-lib has any check whether the application had called
snd_pcm_sw_params() or
it provide default values for those software parameters (e.g.
start_threshold, stop_threshold)
when the application only call snd_pcm_hw_params() and snd_pcm_prepare()

Re: Is calling snd_pcm_sw_params() mandatory ?

[Clemens Ladisch]

Raymond Yau wrote:
> Does alsa-lib has any check whether the application had called snd_pcm_sw_params() or
> it provide default values for those software parameters (e.g. start_threshold, stop_threshold)

The internal snd_pcm_sw_params_default() function does this:

	params->tstamp_mode = SND_PCM_TSTAMP_NONE;
	params->period_step = 1;
	params->sleep_min = 0;
	params->avail_min = pcm->period_size;
	params->xfer_align = 1;
	params->start_threshold = 1;
	params->stop_threshold = pcm->buffer_size;
	params->silence_threshold = 0;
	params->silence_size = 0;


Regards,
Clemens