On Thu, 15 Mar 2018 14:39:33 +0100, Oleksandr Andrushchenko wrote: > > On 03/15/2018 03:23 PM, Takashi Iwai wrote: > > 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. > > > Clear, thank you > >>> 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. > Yes, I now start thinking of the same, e.g. if we pass > all 5 parameters (mask for formats and intervals for rate, channels, > buffer and period), then on backend side I can do something like: > > 1. snd_pcm_hw_params_any > 2. snd_pcm_hw_params_set_format_mask > 3. snd_pcm_hw_params_set_rate_minmax > 4. snd_pcm_hw_params_set_channels_minmax > 5. snd_pcm_hw_params_set_buffer_size_minmax > 6. snd_pcm_hw_params_set_period_size_minmax > > So, when finished the above confirms that configuration is possible. > The only concern here is that so many calls on backend side > might introduce start-up latency on frontend side though > > > IOW, the query stuff won't be modal, it just tries to reduce the given > > configuration space to the acceptable ranges. > Do you think the above solution with 5 parameters and the > corresponding snd_pcm_hw_params_set_xxx calls will do? I guess so, but let's model & test :) thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
