linux-kernel - Re: [RFC PATCH v2 0/6] ALSA: compress: add support to change codec profile in gapless playback

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Date:   Thu, 23 Jul 2020 18:35:22 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        broonie@...nel.org, perex@...ex.cz, tiwai@...e.com,
        lgirdwood@...il.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, ckeepax@...nsource.cirrus.com
Subject: Re: [RFC PATCH v2 0/6] ALSA: compress: add support to change codec
 profile in gapless playback

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?

> I have no big objection to add a new ioctl if other people agree,
> though.
> 
> 
> thanks,
> 
> Takashi

-- 
~Vinod