Something really terrible is happening when encoding 20Hz sine wave
2019-08-18 16:44:45
I decided to test what happens when encoding 20hz sine wave with Opus (this is something that can easily be in "real music", so why not), and to my big surprise, it fails spectacularly. I used this setting "--bitrate 128" and nothing else (all else is on default). The bitrate at the end is 263 kbps, almost as high as the source file in 24 bit FLAC. It also sounds very obviously different from original, there's a lot of distortion that wasn't there. (yes I did ABX, see below, also, easiest ABX ever even at very low loudness level) I tried to do the same with quieter signal (to check if maybe encoder is just overflowing something inside) but there's virtually no difference, same problem with inflated bitrate and non transparent sounding. Also tried using different build of opusenc (the one came from foobar2000 encoder pack), again, same issues. Is it a legit problem with Opus? Or am I using some outdated version or doing something wrong? 2 versions that I tried:opusenc --version opusenc opus-tools 0.1.10 (using libopus 1.1.2) Copyright (C) 2008-2017 Xiph.Org Foundation wine ~/Documents/foobar2000/encoders/opusenc.exe --version opusenc opus-tools 0.2-3-gf5f571b (using libopus 1.3.1) Copyright (C) 2008-2018 Xiph.Org Foundation foo_abx 2.0.6c report foobar2000 v1.4.6 2019-08-18 18:40:16 File A: 20hz 30 seconds.flac SHA1: 692b1d490bbb37b937fefbf0bcba8998f810990c File B: 20hz 30 seconds.opus SHA1: a76f486c75d2675b634a1f49808ab0af9898b00d Output: DS : Out: default Crossfading: NO 18:40:16 : Test started. 18:40:28 : 01/01 18:40:43 : 02/02 18:40:58 : 03/03 18:41:07 : 04/04 18:41:19 : 05/05 18:41:26 : 06/06 18:41:31 : 07/07 18:41:35 : 08/08 18:41:41 : 09/09 18:41:47 : 10/10 18:41:56 : 11/11 18:42:03 : 12/12 18:42:07 : 13/13 18:42:13 : 14/14 18:42:18 : 15/15 18:42:23 : 16/16 18:42:23 : Test finished. ---------- Total: 16/16 p-value: 0 (0%) -- signature -- 1631b7e7986adb72438b4f7b8fc660dd1d8077d4