On 03/15/2018 01:59 PM, Takashi Sakamoto wrote:
Hi,
On Mar 15 2018 19:45, Oleksandr Andrushchenko wrote:
Is it possible for user-space to reduce configuration space
with snd_pcm_hw_params_set_rate_minmax and then change it
with another snd_pcm_hw_params_set_rate_minmax with values
out of the reduced config?
For example, the initial min/max is 44100/48000 and I set 44100
first, e.g.
snd_pcm_hw_params_set_rate_minmax(handle, hw_params, 44100, 0, 44100, 0)
and then want
snd_pcm_hw_params_set_rate_minmax(handle, hw_params, 48000, 0, 48000, 0)
Obviously, the last call fails as we have already a reduced
space of [44100; 44100].
Is there a way I can still set the range to [48000; 48000]?
Thank you,
Oleksandr
P.S. This is in context of work done for [1]
[1] https://www.spinics.net/lists/alsa-devel/msg75382.html
We can't. Once shrinking available interval of a parameter, we cannot
expand it again without initializing the parameter on memory object for
'struct snd_pcm_hw_params_t', in which actual layout is never disclosed
to user applications.
So, this effectively means that this is a one way road, if you need to
change
some parameter you'll need to start all over, so the whole configuration
space remains consistent :(
If you can initialize whole the parameters, snd_pcm_hw_params_any() is
available for your purpose, then set min/max rate again.
This is what I do now but...
But just for
one of the parameters, in my opinion, we need to open an internal API;
snd_pcm_hw_param_any()[1].
IMO, this will lead to the false assumption that configuration is possible.
For example, I set 4 channels and 44100, but then, after
snd_pcm_hw_params_any,
set 48000 and might assume that the configuration is still possible. But
this may not
be true: it is true for the configuration returned by snd_pcm_hw_param_any
as we don't know about 4 channels yet. But might not be allowed if we
want 4 channels
and 48000 at the same time.
[1]
http://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=src/pcm/pcm_params.c;h=608a2324cb268f84d91f67c53d979521678f4edb;hb=HEAD#l107
Regards
Takashi Sakamoto
Thank you very much for explanation,
Oleksandr
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