[Ffmpeg-devel] alsa input / output

Michael Niedermayer michaelni
Wed Mar 21 00:57:20 CET 2007


Hi

On Wed, Mar 21, 2007 at 01:15:51AM +0300, Vladimir Mosgalin wrote:
> Hi Rich Felker!
> 
>  On 2007.03.20 at 16:18:19 -0500, Rich Felker wrote next:
> 
> 
> Well.. sorry for OT but I really think that your point on this is VERY
> wrong.
> 
> > Of couse, as an aside I strongly question the usefulness of lots of
> > this "functionality". It seems more like bloat to me. If the hardware
> > doesn't support a particular samplerate it should simply require the
> > application to provide a supported samplerate, rather than doing
> > horribly-painful-to-listen-to nearest-neighbor resampling in the
> > library level...
> 
> That's exactly the problem you get with device interface; it is just
> supposed to "work". But with alsa accessed through library interface,
> you can do anything you desire, when your applications doesn't support
> this. And you mean application should _always_ use built-in
> resamplers? THAT is the right way to get painful-to-listen-to sound,
> because most of resamplers will suck. With alsa, however, you just
> choose whatever you want, depending on your CPU and personal choice
> (believe it or not, but SRC_SINC_FASTEST sounds better than
> SRC_SINC_BEST_QUALITY and all other SRC_SINC libsamplerate filters to
> me).

so the low quality resampler from libsamplerate sounds better to you then
the high quality ones from libsamplerate, while i dont have much faith
in libsamplerate i cant belive that their fast low quality code sounds
better then their hq code, maybe your audio hardware is broken and the
additional low pass filtering done by low quality resamplers mask that
your furher comment below points strongly in that direction, only very
odd hardware is limited to 24bit/sample

besides this it would be interresting to run proper double blind tests
between libsamplerate and the lavc resampler, if libsamplerate beats us
it would be trivial to use their filter, after all samplerate conversation
is just a trivial linear equation with coefficients choosen to please
the latest audophile trend


[...]
> Another thing, while I'm on it: my current soundcard supports only one
> stream of 24-bit audio padded into S32_BE packets. Period. Most
> applications never ever heard about such format, even latest jack (you
> have to use patched/svn one for that) only knows about 24-bit padded
> into S32_LE. And even more fancy soundcards exist. You _can't_ support
> all this, together with configuration, in end user applications.
[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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