On Thu, 15 Mar 2018 13:20:14 +0100, Oleksandr Andrushchenko wrote: > > 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 :( Yes, that's the design. The only way to expand is to reset the whole, space and reduce again to the given size. > > 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. Right. At the point where snd_pcm_hw_params_any() is called, the whole configuration gets reset. That's the reason I thought we may need to pass all 5 parameters in the query protocol. IOW, the query stuff won't be modal, it just tries to reduce the given configuration space to the acceptable ranges. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
