[alsa-devel] Set eapd to follow stream on or off

[Kailang]

> At Tue, 20 May 2014 17:20:44 +0800,
> Kailang wrote:
>>
>>
>> > At Tue, 20 May 2014 16:52:43 +0800,
>> > Kailang wrote:
>> >>
>> >>
>> >> > At Tue, 20 May 2014 15:15:49 +0800,
>> >> > Kailang wrote:
>> >> >>
>> >> >> Hi Takashi,
>> >> >>
>> >> >> HP machine had pop noise via speaker.
>> >> >> If EAPD on or off, speaker will have pop noise.
>> >> >> So, they want to set eapd to follow with stream on or off.
>> >> >
>> >> > I can apply this as is, but still I wonder whether this results in
>> >> > other problems.  Doing EAPD on/off there means that it happens far
>> >> > more often.  For example, what happens if you do like below?
>> >> >
>> >> >     while true; do
>> >> >       echo -n > /dev/snd/pcmC0D0p
>> >> >     done
>> >> >
>> >> > And, what if the device is resumed from power-saving by an audio
>> >> > playback?  Immediately after the power up, it'll start the 
>> >> > streaming,
>> >> > so it'll turn on EAPD.
>> >> >
>> >> > That said, isn't it just a need for some delay before EAPD on/off?
>> >>
>> >> No, eapd on or off will cause pop noise.
>> >
>> > Does it do always?
>> No, pop noise just one pop sound. It can not remove by software.
>> But this machine need to do this always.
>
> So, doing EAPD on/off often is rather worse.  It's what your patch
> does.
>
> Once again: did you try the script above?  If the pop noise always

I had try it on my develop machine. I have no HP issue machine on my site.

> happens, the operation like above is the worst scenario.
>
> Then, let's think again how to *reduce* it.  We need one EAPD on at
> least after each power up.  But it's needed only when you actually
> plays a stream.  That is, we need only enable EAPD at playback stream
> open, but leave EAPD as is at close.
>

[we need only enable EAPD at playback stream open, but leave EAPD as is at 
close.]
Yes.
So, I need to create eapd low in alc269_shutup. Right?

>
> Takashi
>
>> >> Our customer just want to do eapd on when stream is open.
>> >> The pop noise will not clear. Because music gain was biger than pop
>> >> noise.
>> >
>> > Opening a stream doesn't mean that it follows the loud sound
>> > immediately.  The script above wouldn't produce any sound but just
>> > does open/close the stream.  Did you try that?
>> >
>> >
>> > Takashi
>> >
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>>