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 14:20:14 +0200 Message-ID: <9cf1073b-97ec-a3f5-a08a-5c54f5d92c4a@gmail.com> References: <8f76589f-d64f-e6c2-db4a-57319e68ec3d@gmail.com> <084894a2-8107-05ab-6f6c-7418c505f3c4@sakamocchi.jp> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-lf0-f41.google.com (mail-lf0-f41.google.com [209.85.215.41]) by alsa0.perex.cz (Postfix) with ESMTP id 5DA82267252 for ; Thu, 15 Mar 2018 13:20:17 +0100 (CET) Received: by mail-lf0-f41.google.com with SMTP id t132-v6so9828701lfe.2 for ; Thu, 15 Mar 2018 05:20:17 -0700 (PDT) In-Reply-To: <084894a2-8107-05ab-6f6c-7418c505f3c4@sakamocchi.jp> 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 Sakamoto , alsa-devel@alsa-project.org Cc: Takashi Iwai List-Id: alsa-devel@alsa-project.org 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