From mboxrd@z Thu Jan 1 00:00:00 1970 From: bugtrack@alsa-project.org Subject: [ALSA - lib 0000385]: Rate conversion plugin generates noise on frequency reduction Date: Fri, 22 Oct 2004 16:34:47 +0200 Sender: alsa-devel-admin@lists.sourceforge.net Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from bugtrack.alsa-project.org (gate.perex.cz [82.113.61.162]) by alsa.alsa-project.org (ALSA's E-mail Delivery System) with ESMTP id C4FBA29A for ; Fri, 22 Oct 2004 16:34:47 +0200 (MEST) Errors-To: alsa-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org A NOTE has been added to this issue. ====================================================================== ====================================================================== Reported By: fmoraes Assigned To: perex ====================================================================== Project: ALSA - lib Issue ID: 385 Category: pcm - digital audio Reproducibility: always Severity: major Priority: normal Status: assigned ====================================================================== Date Submitted: 07-13-2004 19:46 CEST Last Modified: 10-22-2004 16:34 CEST ====================================================================== Summary: Rate conversion plugin generates noise on frequency reduction Description: When reducing the frequency, the pcm_rate plugin causes noise on the output data. This has been tested with both the snd-cs46xx and snd-emu10k1x drivers and the following .asoundrc can be used to recreate the output in a file: pcm.CS46xx { type hw card 0 } pcm.filetest { type file slave { pcm "CS46xx" } file "/home/fmoraes/test-out.raw" format "raw" } pcm.test { type rate slave { pcm "filetest" format "S16_LE" rate 8000 } } Playing a 48Khz file will cause noticeable noise on the output (noise is more noticeable the lower the target frequency is). ====================================================================== ---------------------------------------------------------------------- Tobias Diedrich - 10-21-04 17:01 ---------------------------------------------------------------------- I second that. Downsampling even from 48000Hz to 44100Hz produces very noticable artifacts, which sound very much like nearest neighbour resampling artifacts and are especially evident in high pitched vocals. It would also be nice to implement better resampling methods than just linear resampling, AFAICS from the source polyphase and bandlimited resampling are planned but not yet implemented. ---------------------------------------------------------------------- perex - 10-22-04 16:34 ---------------------------------------------------------------------- The reported problem should be solved in 1.0.7rc releases. At the time, we don't have free resources to write code for another resampling method. Also, there are several problems to use methods based on sample history. Issue History Date Modified Username Field Change ====================================================================== 07-13-04 19:46 fmoraes New Issue 07-15-04 14:07 perex Status new => assigned 07-15-04 14:07 perex Assigned To => perex 10-21-04 16:57 Tobias DiedrichIssue Monitored: Tobias Diedrich 10-21-04 17:01 Tobias DiedrichNote Added: 0002223 10-22-04 16:19 perex Project ALSA - driver => ALSA - lib 10-22-04 16:20 perex Category OTHERS => pcm - digital audio 10-22-04 16:34 perex Note Added: 0002244 ====================================================================== ------------------------------------------------------- This SF.net email is sponsored by: IT Product Guide on ITManagersJournal Use IT products in your business? Tell us what you think of them. Give us Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more http://productguide.itmanagersjournal.com/guidepromo.tmpl