Return-Path: Message-ID: <492FFF3B.7000702@powercraft.nl> Date: Fri, 28 Nov 2008 15:24:59 +0100 From: Jelle de Jong MIME-Version: 1.0 To: Marcel Holtmann CC: Jaska Uimonen , linux-bluetooth@vger.kernel.org Subject: Re: [RFC/PATCH] sbc: new filtering function for 8 band fixed point encoding References: <1227879337.20555.12.camel@esdhcp03999.research.nokia.com> <1227881932.31311.2.camel@violet.holtmann.net> In-Reply-To: <1227881932.31311.2.camel@violet.holtmann.net> Content-Type: text/plain; charset=UTF-8 List-ID: 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