Hi everyone, After bitching for a while about the poor quality of the resampler used by the plug: interface, I've finally put code where my mouth is and wrote a BSD-licensed resampler. While the code lives within the Speex project, it's trivial to get out of there. All you need to grab is: http://svn.xiph.org/trunk/speex/include/speex/speex_resampler.h http://svn.xiph.org/trunk/speex/libspeex/resample.c and then you need to compile with -DOUTSIDE_SPEEX The quality is similar to what you get with libsamplerate, but the license is BSD, so there should be no issue using it within libasound. There are 11 quality settings (0-10) and even the lowest quality provided is already miles better than the linear interpolation currently being done (which creates insane amounts of aliasing when doing things like upsampling from 8 kHz to 48 kHz). I'm also willing to help whoever is interested in adding support for it. Partly related to that is another annoyance I found in the plug: converters. The conversion between 24-bit samples into 16-bit samples appears to be done by truncating rather than by rounding, which introduces more quantisation noise and also a small DC bias. The fix for that is fairly simple: in all the places where you have something like: out[i] = in[i] >> 8; it should be replaced by: out[i] = (in[i]+128) >> 8; I would have submitted a patch for that, but I was never able to figure out how that part of the code works. Jean-Marc P.S. Please keep me in CC since I'm not subscribed to the list. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-devel
