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Thu, 6 Aug 2020 18:28:44 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id D6854F80159; Thu, 6 Aug 2020 18:28:41 +0200 (CEST) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id C2F07F80124 for ; Thu, 6 Aug 2020 18:28:30 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz C2F07F80124 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 1BF2BAC48; Thu, 6 Aug 2020 16:28:48 +0000 (UTC) Date: Thu, 06 Aug 2020 18:28:30 +0200 Message-ID: From: Takashi Iwai To: Vinod Koul Subject: Re: [RFC PATCH v2 0/6] ALSA: compress: add support to change codec profile in gapless playback In-Reply-To: <20200806043010.GC12965@vkoul-mobl> References: <20200721170007.4554-1-srinivas.kandagatla@linaro.org> <20200723130522.GB12965@vkoul-mobl> <20200723155612.GC12965@vkoul-mobl> <20200806043010.GC12965@vkoul-mobl> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Cc: alsa-devel@alsa-project.org, ckeepax@opensource.cirrus.com, linux-kernel@vger.kernel.org, lgirdwood@gmail.com, tiwai@suse.com, broonie@kernel.org, Srinivas Kandagatla X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Thu, 06 Aug 2020 13:08:13 +0200, Vinod Koul wrote: > > On 23-07-20, 22:33, Takashi Iwai wrote: > > On Thu, 23 Jul 2020 17:56:12 +0200, > > Vinod Koul wrote: > > > > > > On 23-07-20, 15:17, Takashi Iwai wrote: > > > > On Thu, 23 Jul 2020 15:05:22 +0200, > > > > Vinod Koul wrote: > > > > > > > > > > On 23-07-20, 14:38, Takashi Iwai wrote: > > > > > > On Tue, 21 Jul 2020 19:00:01 +0200, > > > > > > Srinivas Kandagatla wrote: > > > > > > > > > > > > > > For gapless playback it is possible that each track can have different > > > > > > > codec profile with same decoder, for example we have WMA album, > > > > > > > we may have different tracks as WMA v9, WMA v10 and so on > > > > > > > Or if DSP's like QDSP have abililty to switch decoders on single stream > > > > > > > for each track, then this call could be used to set new codec parameters. > > > > > > > > > > > > > > Existing code does not allow to change this profile while doing gapless > > > > > > > playback. > > > > > > > > > > > > > > This patchset adds new SNDRV_COMPRESS_SET_CODEC_PARAMS IOCTL along with > > > > > > > flags in capablity structure to allow userspace to set this new > > > > > > > parameters required which switching codec profile, either for gapless > > > > > > > or cross fade usecase. > > > > > > > > > > > > One idea that came up at the previous audio conference regarding this > > > > > > implementation was to just allow SET_PARAMS during the stream is > > > > > > running (only if the driver sets the capability) instead of > > > > > > introducing yet a new ioctl and an ops. > > > > > > Would it make sense? > > > > > > > > > > That does sound good but only issue would be that we need to somehow > > > > > mark/document that buffer info is useless and would be discarded, how do > > > > > we do that? > > > > > > > > Yes, the buffer and no_wake_mode can be ignored in the gapless > > > > re-setup. Is your concern only about the documentation? Or something > > > > else needs to be changed significantly? It's a new scheme in anyway, > > > > so the documentation update is required... > > > > > > My concern is potential abuse of API down the road, if you feel it is > > > okay, I am okay with the proposal > > > > If this can be potentially dangerous, it shouldn't be used, of course. > > What kind of scenario could it be? > > I can think of users trying to invoke this incorrectly, right now we > would reject this. > > Maybe, we can add checks like, if next_track is set and then copy the > codec params only to prevent any misuse. > > Do you think that would be okay? Yes, it's the same condition check that was proposed for the new ioctl. Takashi