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 14:38:09 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     broonie@...nel.org, vkoul@...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 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?

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


thanks,

Takashi