Re: [RFC/PATCH] sbc: new filtering function for 8 band fixed point encoding

Jaska Uimonen
2008-11-28T15:20:06Z

Hi,

I did the git clone this morning and made the patch on top of that.

Johan already came to tell me that I have whitespace instead
of tabs in the changed parts. Sorry about that, I'll fix it.
He said it will take 1 minutes to fix that but it was
at least 1/2 hour with emacs :)

br,
Jaska

On Fri, 2008-11-28 at 15:24 +0100, ext Jelle de Jong wrote:
> Marcel Holtmann wrote:
> > Hi Jaska,
> >
> >> I did some testing on the current 8 band fixed point
> >> encoding and it seems to attenuate frequencies below 800Hz
> >> and above 18kHz. There might be some other stuff happening
> >> also, because at least to me the bass seemed to lack some
> >> "definition".
> >>
> >> I didn't quite understand how the current tables are calculated
> >> and how the filtering works so I wrote a new filtering function
> >> and calculated new filter tables for it. It is written
> >> using 16 bit fixed point without any platform specific optimizations.
> >> I only unrolled some loops etc. I tried to follow the
> >> flow chart in MPEG-1 annex c.
> >>
> >> With this new filtering the low and high frequencies are there, but
> >> I haven't done any more thorough testing. At least it sounds
> >> a little bit better to my ears :)
> >
> > thanks for looking at it. I am seriously lost when it comes to audio
> > codecs and my ears normally don't count for much.
> >
> > So do you think we should throw all away any you start over providing a
> > correct implementation with fixed point integer and then we start
> > optimizing step by step (while testing against SBC conformance) or how
> > should we continue. For sure we have to fix our codec.
> >
> > Regards
> >
> > Marcel
>
> Hi Jaska, Thank you so much for improving the codecs :-D it was on my
> long standing wish list. You want to receive a few Dutch stroopwafels
> for your efforts :-D
>
> Is the patch you provided working against the latest git? Marcel would
> you be willing to review the patch for code style, hidden issues etcetera.
>
> I would love to test this patch this weekend and apply it to the latest git.
>
> I am an heavy stereo bluetooth user and will notice glitches and quality
> distortions on my bluetooth speakers and headsets.
>
> Best regards,
>
> Jelle