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Subject: Re: Ugly noise at soings begining

Re: Ugly noise at soings begining

From: Salokyn <nicolas.gif_at_free.fr>
Date: Thu, 13 Aug 2009 23:50:34 +0200

Le 13/08/2009 19:00, Mike Hodson a écrit :
> On Wed, Aug 12, 2009 at 11:20 AM, Salokyn<nicolas.gif_at_free.fr> wrote:
>> Hi,
>>
>> Since some time (maybe 3.0) I got a loud white noise when play songs after
>> having pushed stopped. This never happened before.
>>
>> My player is an iAudio X5 with RB r22166-090805. I found a similar problem
>> on the forum here : http://forums.rockbox.org/index.php?topic=11216.0 (I
>> can't log on the forum so I post here)
>
> I have a Sansa E250 (as mentioned in your linked forum post) and have
> noticed the problem you describe for a very long time. I did not
> however notice it with an iRiver H320. In my case, It seems to be the
> flash reading buffering the track which causes electrical noise on the
> internal circuit board. I hear the slight noise every time I see the
> flash chip access indicator in the upper right of my screen.
>
> One thing I did notice recently however, is that with some new
> headphones (rated at 105dB SPL @ 1mW mind you, so -very- sensitive)
> the noise is noticeably louder -- likely due to the constant amplitude
> of whatever pulses read the SD card, and the lower amplitude of the
> audio signal required to generate the same amount of dB in my
> headphones.
>
>> Once the noise begins, it continues whatever I change tracks or stop/play,
>> even if I skip tracks enough to force buffer to fill again.
>> It happens after pushing stop and then open a track or resume the current
>> one.
>
>> It doesn't happen if I change track without pushing stop or when I just turn
>> my player on (new trak or resume).
>
> Due to how the buffer acts, it will fill to a set memory size, fitting
> however many songs fit in said memory size into the memory. This
> minimizes disk/flash reads and prolongs battery life as much as
> possible, by not spinning the disk up any more than needed.
>
> Your 'doesn't happen when i just turn my player on' report however
> seems inconsistent with a 'buffering' operation... Are you saying that
> once you turn the player on from a cold start, listening to the
> headphones the entire time before music plays, you do not hear it at
> all?
>
> I would speculate that if you listened, from the moment you engaged
> the power button at a total power off state, until the first disk read
> had finished (to buffer the first and subsequent tracks) that there
> would be *some* similar noise.
>
>> To stop the noise, I must restart my player or reduce the sound level and
>> rise it back as suggested on the forum post.
>
> I believe the only thing lowering and raising the sound level is
> doing, is allowing the disk to finish buffering to memory and then
> spinning down... As for restarting, I am very hesitant to say that
> 'fixes' the problem, without a full test, headphones on, from startup
> to the beginning of music playback.
>
> If I am wrong in my guess as to what this is, please let us know!
>
> Mike

Hi Mike, thanks for answering.

First of all, it's not an electric noise you could hear beyond the
music. It's a very loud white noise that replace the music. It's
unbearable, you can't keep the headphones one second on your hears as
the noise is loud. Anyway the noise is sensible to the volume.

> Are you saying that
> once you turn the player on from a cold start, listening to the
> headphones the entire time before music plays, you do not hear it at
> all?

Exactly. This does not happen until I push stop (long push on PLAY
button on X5). I checked on the "buffering thread" screen in debug. X5
has 12MB buffer and the noise as nothing to do with the buffer filling.

I think it's a bug about STOP function, not buffering.

Nicolas

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Received on 2009-08-13


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