[alsa-devel] Set eapd to follow stream on or off
kailang at realtek.com
Tue May 20 11:20:44 CEST 2014
> 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
> 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?
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