[ Thread Index |
Date Index
| More lists.liballeg.org/allegro-developers Archives
]
Elias Pschernig <info@xxxxxxxxxx> wrote:
>On Sat, 21 Apr 2012 14:17:23 -0400
>SiegeLord <slabode@xxxxxxxxxx> wrote:
>
>> On 04/21/2012 06:08 AM, Elias Pschernig wrote:
>> > Oh, good catch, didn't think of that. But then it should only have
>> > happened with linear resampling. I also don't understand why it's
>> > not reproducible here. Oh well, if this really fixes it I'll just
>> > conclude that my ears or headphones are rather bad. Or that
>> > pulseaudio does some unasked for post-processing, wouldn't
>> > surprise me the least.
>>
>> Yes, with point resampling the metallic noise is still there. It was
>> there even before these patches, however, so it's just an
>> illustration of how bad point resampling is.
>>
>> As for why you couldn't hear it... here's two spectra of the ex_synth
>
>> output (peak on the left is the frequency of the sine wave - 660 Hz,
>> and all other peaks are junk introduced by resampling).
>>
>> http://img403.imageshack.us/img403/1895/resamplingspectra.png
>>
>> I suppose there are quite a few peaks in the very high frequency
>> ranges, so they can easily start approaching hardware limitations.
>>
>>
>
>Interesting. So yeah, I suppose if you'd give me a recording of both
>I'd still hear no difference.
>
>Something else I saw is with alsa I get very small buffers, alternating
>between 32 and 12 samples. However the linear interpolation right now
>will not go over a buffer boundary. So there's a step every 32/12
>samples. I obvously won't hear a difference - but might be worth fixing
>(although it doesn't look easy to fix, probably would need to delay all
>audio by one sample and then somehow keep the very last sample of each
>buffer around for the next buffer to interpolate the first sample
>against).
Yes. Turns out to be not too hard, fortunately.
>
>The real question also is why our alsa driver behaves in this way,
>tiny fragments likely will have all other kinds of troubles
>(maybe also explains the crackling Peter mentioned?)
>
Haven't investigated this yet.
Peter
>------------------------------------------------------------------------------
>For Developers, A Lot Can Happen In A Second.
>Boundary is the first to Know...and Tell You.
>Monitor Your Applications in Ultra-Fine Resolution. Try it FREE!
>http://p.sf.net/sfu/Boundary-d2dvs2
>--
>https://lists.sourceforge.net/lists/listinfo/alleg-developers