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

[Kailang]

> 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.

>
>> 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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