From: Maik M. <mai...@go...> - 2024-07-26 04:07:26
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Hello Ross, -q4 already has the full Huffman code search. (-q5 does not) I'm currently not quite sure any LAME developer with commit access (for whatever patch approach) is following this discussion, though. Best regards, Maik Am 26.07.24 um 01:06 schrieb Ross Levis via Lame-dev: > I'm not sure that's a good idea. I believe better quality settings use more aggressive Huffman encoding to pack the file smaller. > That will be the main reason it's taking less time encoding at -q4. > > -----Original Message----- > From: Maik Merten via Lame-dev [mailto:lam...@li...] > Sent: Friday, 26 July 2024 3:15 am > To: lam...@li... > Subject: Re: [Lame-dev] CBR/ABR quality regressions for q0, q1, q2 and q3 > > Hello, > > I updated the bug report with, perhaps, a better constructed patch: > > https://sourceforge.net/p/lame/bugs/516/ > > This latest patch simply maps the quality levels 0, 1, 2 and 3 to 4, > similarly to how the quality-levels are handled for the new VBR mode. > > Of course, it would be best to find out *why* the settings 0 to 3 don't > work well with CBR and ABR and fix *that*, but this is a very > non-interfering (I hope) way to fix the symptoms. It even gives a neat > speed-boost. > > Hopefully, any of the LAME developers with commit access might have a > look at that trivial patch. > > Best regards, > Maik > > > Am 12.07.24 um 18:57 schrieb Maik Merten: >> 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 |