Hello,
I have made some extensive study on the compression performance of Linux's
SBC audio codec in comparison to the reference implementation.
I am sorry to say that the audio quality of the open source version of SBC
is far worse than the reference implementation.
Can anybody confirm these results?
Do you have any idea why the performance is so worse?
With best regards,
Christian
--------------------------------------------------------
Dr.-Ing. Christian Hoene
Computer Networks and Internet, University of T=FCbingen
Sand 13, 72076 T=FCbingen, Germany, Phone +49 7071 2970532
http://net.informatik.uni-tuebingen.de/~hoene
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Hello,
Thanks for doing those tests, we never really have a method for
testing the sbc codec, so PEAQ could be a good start. By looking the
results it seems that our decoder is not really in good shape, which
is not a surprise since we normally only use the encoder part. As for
comparison with the reference implementation, bluez sbc codec does not
use floating point as the reference codec seems to be using, so this
may well be impacting on quality, although we probably gain some
speed.
Other points we might need to consider:
- Test with different audio source/parameter. (48000hz/mono/28
bitpool is not that common to be used as reference)
- Mono seems to surfer from quality problems which may cause the problem.
- Consider working on a gstreamer element for doing live tests based
on ITU BS.1387 (PEAQ)
- Also consider using liboil as alternative for using floating point.
BTW, don't assume something is bad just because it produces different
results than the reference, as far I can tell you one cannot really
notice _any_ difference between bluez sbc codec and logitech freepulse
e(enhanced)sbc, so on real world we are not that _bad_.
-- =
Luiz Augusto von Dentz
Engenheiro de Computa=E7=E3o
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Hi Brad,
> > I am sorry to say that the audio quality of the open source version of SBC
> > is far worse than the reference implementation.
>
> If you are using the standalone "sbc" project at sourceforge, then you
> should try the version inside bluez. The standalone used to simply be
> slower, but we identified & fixed some quality issues too that should
> be backported.
the standalone version should not be used at all at the moment. All
efforts should go into the version included in bluez-4.x.tar.gz.
Regards
Marcel
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Christian
> I am sorry to say that the audio quality of the open source version of SBC
> is far worse than the reference implementation.
If you are using the standalone "sbc" project at sourceforge, then you
should try the version inside bluez. The standalone used to simply be
slower, but we identified & fixed some quality issues too that should
be backported.
--
Brad Midgley
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Hi Christian,
> I have made some extensive study on the compression performance of Linux's
> SBC audio codec in comparison to the reference implementation.
>
> I am sorry to say that the audio quality of the open source version of SBC
> is far worse than the reference implementation.
>
> Can anybody confirm these results?
> Do you have any idea why the performance is so worse?
are you talking about the encoder or the decoder. For the encoder, I
can't see the big difference. For the decoder you can clearly hear that
we get the volume wrong.
Regards
Marcel
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