[alsa-devel] Bugs on aspire one A150

[Takashi Iwai]

At Sat, 22 Nov 2008 21:00:18 +0200,
Maxim Levitsky wrote:
> 
> Maxim Levitsky wrote:
> > Andreas Mohr wrote:
> >> Hi,
> >>
> >> On Wed, Nov 12, 2008 at 07:07:04PM +0200, Maxim Levitsky wrote:
> >>> I pretty much studied the datasheet and driver, and this is what I 
> >>> found:
> >>> btw, my acer 5720 and aspire one share same ALC268.
> >>> Some stuff is trivially fixable, some seems to be unfixable at all:
> >>
> >> Wow, what an extremely in-depth analysis!
> >> I just intended to dive into getting mic routing corrected myself,
> >> thus you saved me a lot of time!
> >>
> >>> model=acer is used on my regular laptop.
> >>> model-acer-aspire is used on aspire one laptop, and it needs to be 
> >>> renamed, as both are aspire.
> >>
> >> +1 (your analysis of both being rather different - as already pondered -
> >> confirms this necessity)
> >>
> >>> And now for unfixable problems:
> >>>
> >>> 1) There is strong DC offset on all inputs.
> >>> it is even different on left/right and depends on capture volume.
> >>> I tried to change the VREF only param that could help, but it doesn't.
> >>> I feel that this is hardware flaw.
> >>> (It is possible that voltage on inputs is created by circuit made by 
> >>> acer, and then ALC268 amplifies it.)
> >>
> >> Sounds like really bad circuit design then.
> >> One would think that the Intel HDA architecture might have builtin
> >> measures to compensate for this if needed? DC offset issues on
> >> soundcards aren't exactly a new phenomenon after all...
> >>
> >>> Lastly I noticed that datasheet mentions so called 'coefficients':
> >>> the codecs exposes lots of internal and undocumented registers using 
> >>> set address/ get/set value scheme.
> >>> maybe some of above bugs are fixable there, but ether realtek has to 
> >>> provide data for that or reverse engineering of
> >>> windows driver is required.
> >>
> >> I've actually had a peek at the .inf files since I thought that it would
> >> already contain register values in those registry keys that it creates on
> >> install, but yeah, that's all in-driver it seems.
> >> Probably time to ask Acer about specifics, especially since I didn't spot
> >> any hda-intel changes in their linux-2.6.23.9lw source.
> >>
> >> Thank you very much,
> >>
> >> Andreas Mohr
> > 
> > Small update:
> > 
> > 1) The dc offset isn't present on aspire one, really is a circuit design 
> > bug I guess 2) Internal mic works perfectly on aspire one, can reproduce 
> > the strange behaver at all,
> > Probably this was mixer bug.
> Finally, I found how to reproduce that bug,
> I mean to get normal volume on internal mic, I have to increase volume
> only on left or right channel.
> 
> So, this happens always, and _only_ when recording _mono_ sound from internal
> mic.
> 
> Since hardware doesn't support hardware mono input, tested with -D hw:0
> I suspect this to be alsa-lib bug, any ideas?
> Happens with arecord -D plughw:0 -c1 .

What does show with -v option?


Takashi