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From: Takashi Iwai <tiwai@suse.de>
To: Vinod Koul <vkoul@kernel.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
	broonie@kernel.org, perex@perex.cz, tiwai@suse.com,
	lgirdwood@gmail.com, alsa-devel@alsa-project.org,
	linux-kernel@vger.kernel.org, ckeepax@opensource.cirrus.com
Subject: Re: [RFC PATCH v2 0/6] ALSA: compress: add support to change codec profile in gapless playback
Date: Thu, 23 Jul 2020 22:33:57 +0200	[thread overview]
Message-ID: <s5hy2naotsa.wl-tiwai@suse.de> (raw)
In-Reply-To: <20200723155612.GC12965@vkoul-mobl>

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?


thanks,

Takashi

WARNING: multiple messages have this Message-ID (diff)
From: Takashi Iwai <tiwai@suse.de>
To: Vinod Koul <vkoul@kernel.org>
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 <srinivas.kandagatla@linaro.org>
Subject: Re: [RFC PATCH v2 0/6] ALSA: compress: add support to change codec profile in gapless playback
Date: Thu, 23 Jul 2020 22:33:57 +0200	[thread overview]
Message-ID: <s5hy2naotsa.wl-tiwai@suse.de> (raw)
In-Reply-To: <20200723155612.GC12965@vkoul-mobl>

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?


thanks,

Takashi

  reply	other threads:[~2020-07-23 20:34 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-21 17:00 [RFC PATCH v2 0/6] ALSA: compress: add support to change codec profile in gapless playback Srinivas Kandagatla
2020-07-21 17:00 ` Srinivas Kandagatla
2020-07-21 17:00 ` [RFC PATCH v2 1/6] ALSA: compress: move codec parameter check to a function Srinivas Kandagatla
2020-07-21 17:00   ` Srinivas Kandagatla
2020-07-21 19:56   ` Pierre-Louis Bossart
2020-07-21 19:56     ` Pierre-Louis Bossart
2020-07-21 17:00 ` [RFC PATCH v2 2/6] ALSA: compress: add new ioctl for setting codec parameters Srinivas Kandagatla
2020-07-21 17:00   ` Srinivas Kandagatla
2020-07-21 20:05   ` Pierre-Louis Bossart
2020-07-21 20:05     ` Pierre-Louis Bossart
2020-07-22  8:59     ` Srinivas Kandagatla
2020-07-22  8:59       ` Srinivas Kandagatla
2020-07-22 15:36       ` Pierre-Louis Bossart
2020-07-22 15:36         ` Pierre-Louis Bossart
2020-07-23  4:47         ` Vinod Koul
2020-07-23  4:47           ` Vinod Koul
2020-07-23 13:17           ` Pierre-Louis Bossart
2020-07-23 13:17             ` Pierre-Louis Bossart
2020-07-21 17:00 ` [RFC PATCH v2 3/6] ALSA: compress: add flags to snd_compr_caps to expose dsp caps Srinivas Kandagatla
2020-07-21 17:00   ` Srinivas Kandagatla
2020-07-21 17:00 ` [RFC PATCH v2 4/6] ASoC: compress: add snd_soc_dai_compr_set_codec_params() Srinivas Kandagatla
2020-07-21 17:00   ` Srinivas Kandagatla
2020-07-21 17:00 ` [RFC PATCH v2 5/6] ALSA: compress: bump the version Srinivas Kandagatla
2020-07-21 17:00   ` Srinivas Kandagatla
2020-07-21 17:00 ` [RFC PATCH v2 6/6] ASoC: q6asm-dai: add support to set_codec_params Srinivas Kandagatla
2020-07-21 17:00   ` Srinivas Kandagatla
2020-07-21 20:09   ` Pierre-Louis Bossart
2020-07-21 20:09     ` Pierre-Louis Bossart
2020-07-22  8:59     ` Srinivas Kandagatla
2020-07-22  8:59       ` Srinivas Kandagatla
2020-07-22 14:04   ` Daniel Baluta
2020-07-22 14:04     ` Daniel Baluta
2020-07-23 12:38 ` [RFC PATCH v2 0/6] ALSA: compress: add support to change codec profile in gapless playback Takashi Iwai
2020-07-23 12:38   ` Takashi Iwai
2020-07-23 13:05   ` Vinod Koul
2020-07-23 13:05     ` Vinod Koul
2020-07-23 13:17     ` Takashi Iwai
2020-07-23 13:17       ` Takashi Iwai
2020-07-23 15:56       ` Vinod Koul
2020-07-23 15:56         ` Vinod Koul
2020-07-23 20:33         ` Takashi Iwai [this message]
2020-07-23 20:33           ` Takashi Iwai
2020-08-06 11:08           ` Vinod Koul
2020-08-06 11:08             ` Vinod Koul
2020-08-06 16:28             ` Takashi Iwai
2020-08-06 16:28               ` Takashi Iwai

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