From: Tobias D. <tob...@gm...> - 2024-07-22 13:28:31
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Out of curiosity, I've run diff on files produced by -V9 -q0 and -V9 -q4, and it turns out they are identical. -q does absolutely nothing when using -V. Am 22.07.24 um 14:37 schrieb Tobias Damisch via Lame-dev: > I noticed that -V9 -q0 does sound identical to -V9 -q4 (at least on > my Sony XM3s), also I cannot spot any difference in encoding time > between the two (which I would expect from different -q settings, as is > clearly the case when using -cbr). > > Also AFAIR this has been the case for a very, very long time. > > I don't know if this is to be expected and a trivial observation or if > it does indeed add anything to the conversation. > > Just my 2 cents, > > Tobias > > > Am 12.07.24 um 18:57 schrieb Maik Merten via Lame-dev: >> Hello there, >> >> it has been observed that with CBR and ABR, perceived audio quality >> increases when using faster settings than default. >> >> A discussion regarding this over at HydrogenAudio: >> https://hydrogenaud.io/index.php/topic,126120.0.html >> >> This is very easily noticeable with very low bitrates, but is also >> detectable with the default bitrate of 128 kbps. The discussion thread >> on HydrogenAudio includes samples. >> >> I traced this down to cfg->noise_shaping_amp, which is set to 1 for >> -q3/-q2 and is set to 2 for -q1/-q0. Choosing a value of 0 (as for the >> faster quality settings) improves perceived audio quality. >> >> I opened up a bug report a while back over at >> https://sourceforge.net/p/lame/bugs/516/ with trivial patches and an >> attempt at a theory of why quality might be affected negatively with >> noise_shaping_amp being set to 1 or 2. This, however, is merely >> speculative, as it's not quite clear to me what settings 1 and 2 are >> actually trying to achieve - presumably, those are intended to increase >> quality (and perhaps they do in VBR?), but I don't quite understand the >> reasoning behind those approaches. >> >> While setting noise_shaping_amp to 0 is a trivial thing to do, it might >> also be (pure speculation, again) that the actual root cause is with the >> CBR and ABR encoding loops somehow not interacting properly with >> noise_shaping_amp 1/2 and that a "true fix" might involve tinkering with >> those encoding loops. >> >> How would one progress on this issue? With -q3 being the default >> setting, rather regrettably CBR and ABR encodings are impacted >> negatively by default. >> >> Another, but most likely minor thing: It appears that noise_shaping_stop >> is unused, yet set up by lame_init_qval. I assume this could be removed? >> >> Best regards, >> Maik >> >> _______________________________________________ >> Lame-dev mailing list >> Lam...@li... >> https://lists.sourceforge.net/lists/listinfo/lame-dev > > > _______________________________________________ > Lame-dev mailing list > Lam...@li... > https://lists.sourceforge.net/lists/listinfo/lame-dev |