From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleksandr Andrushchenko Subject: Re: alsalib and snd_pcm_hw_params_set_rate_minmax Date: Thu, 15 Mar 2018 15:39:33 +0200 Message-ID: References: <8f76589f-d64f-e6c2-db4a-57319e68ec3d@gmail.com> <084894a2-8107-05ab-6f6c-7418c505f3c4@sakamocchi.jp> <9cf1073b-97ec-a3f5-a08a-5c54f5d92c4a@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-lf0-f54.google.com (mail-lf0-f54.google.com [209.85.215.54]) by alsa0.perex.cz (Postfix) with ESMTP id 2EE4E267252 for ; Thu, 15 Mar 2018 14:39:35 +0100 (CET) Received: by mail-lf0-f54.google.com with SMTP id f75-v6so10215191lfg.6 for ; Thu, 15 Mar 2018 06:39:35 -0700 (PDT) In-Reply-To: Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Takashi Iwai Cc: alsa-devel@alsa-project.org, Takashi Sakamoto List-Id: alsa-devel@alsa-project.org 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? > > Takashi Thank you, Oleksandr