HydrogenAudio

Lossy Audio Compression => MP3 => MP3 - Tech => Topic started by: banan on 2013-03-03 21:27:39

Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: banan on 2013-03-03 21:27:39
Does anyone know the reason behind disabling the lowpass filter with -V0 but enabling it with -b 320? I mean, if -V0 can handle the high frequencies, then why -b 320 cannot? Hydrogenaudio recommends either -V0 or -b 320 for maximum quality, and so far I thought the major difference between them is the size of the file...
Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: saratoga on 2013-03-03 23:17:29
My random guess is that the low pass was disabled in v0 to encourage the encoder to use a higher bit rate, but that is just a guess.
Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: Kohlrabi on 2013-03-04 05:10:14
Hydrogenaudio recommends either -V0 or -b 320 for maximum quality, and so far I thought the major difference between them is the size of the file...
The major difference is that CBR is pointless to use in lossy encoding, for it defeats the main purpose of lossy encoding, and VBR isn't. If you are looking at very high bitrate solutions already, take a look at halb27's lame3100i encoder (http://www.hydrogenaudio.org/forums/index.php?showtopic=99483) for improved VBR performance.
Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: halb27 on 2013-03-04 08:31:13
With current VBR sfb21 content (the stuff above 16 kHz) is encoded with lower accuracy compared to previous versions. I guess this allowed the Lame dev(s) to skip the lowpass altogether. It's a matter of taste what behavior to prefer, and it doesn't play a major role anyway.
Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: banan on 2013-03-04 09:50:53
Kohlrabi, saying that -b 320 is pointless and offering an improvement over -V0 in the same post is as confusing as removing the lowpass filter from one option an leaving it in another.

halb27, I guess what I'm trying to understand is what behavior Lame devs preferred. The inconsistency between the default settings leaves me a bit puzzled. What about lame3100i? Is the filter on or off by default?
Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: halb27 on 2013-03-04 10:44:09
With 3100i I use a lowpass for any -Vn+ setting by default.
Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: banan on 2013-03-04 11:42:45
I see... So the choice you made for 3100i default settings implies that you recommend to explicitly enable the filter with --lowpass if -V0 option is used, unless personal taste dictates otherwise.
Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: db1989 on 2013-03-04 15:49:29
Which, in itself, is just his personal taste.
Title: lame: lowpass filter disabled for -V0 but enabled for -b 320 -- why?
Post by: Kohlrabi on 2013-03-04 16:00:01
Kohlrabi, saying that -b 320 is pointless and offering an improvement over -V0 in the same post is as confusing as removing the lowpass filter from one option an leaving it in another.
My recommending -V0+ does not change the fact that CBR is pointless*.

*except with broken/old decoders or for very specific streaming situations where ABR does not work