Lame 3.99.5z, a functional extension
Lame 3.99.5z, a functional extension
Sep 18 2012, 23:06
Joined: 9-October 05
From: Dormagen, Germany
Member No.: 25015
You can download it from here.
Whatís the functional extension?
It offers VBR quality settings -V3+ to -V0+ and -V0+eco (economic version of -V0+).
What are -Vn+ and -V0+eco good for?
They improve pre-echo behavior.
Beyond that, they combine the quality advantages of VBR (regarding pre-echo) with the quality advantages of CBR/ABR (with respect to ringing and other tonal issues).
Lame users can be classified into three categories:
a) Users who donít care about rare quality issues and/or care much about small file size.
The common way for these users to work with Lame is to use -V5, -V4, or similar.
b) Users who donít like to have obvious and especially ugly issues in their music even when theyíre rare but who care about file size as well.
The common way for these users to work with Lame is to use -V2, -V3, or similar.
CBR 192 or similar, or ABR in this bitrate range, is an alternative (but seldom used).
c) Users who want overall transparency or at least a quality which comes close to it, and who donít care much about file size.
The common way for these users to work with Lame is to use -V0, -V1, or similar as a VBR method, or to use CBR 320 or 256. Using very high bitrate ABR is an alternative (seldom used).
For users of group b) and c) -Vn+/-V0+eco offers significant quality advantages:
We have two major issue classes with most of the lossy codecs:
- temporal smearing (pre-echo) issues
- ringing (tremolo) and other tonal issues.
Letís look at the worst samples I know for these classes:
- eig (extremely strong temporal smearing)
- lead-voice (extreme ringing, for instance at sec. 0..2)
With samples like these users of group b) canít be very happy when using -V2 or -V3, because the ringing issues are very obvious and ugly. The temporal smearing of eig is pretty obvious as well, especially around sec. 3. Using CBR/ABR 192 or similar is a good procedure to fight the ringing, but temporal smearing is much worse than with VBR, itís real ugly.
Things donít really change when using slightly increased quality settings.
For users of group c) itís exactly the same thing, with quality requirements and quality received just both on a higher level.
So the traditional way of doing things isnít totally satisfactory.
Users of group b) can use -V3+ or -V2+ (recommended) and get much better results in the overall view.
Users of group c) can use -V1+ or -V0+eco (recommended) or -V0+ (recommended for the paranoid like me) and get transparency or close-to-transparency. Sure itís impossible to prove transparency for the universe of music, but itís true for the samples mentioned. And as these are very outstanding samples within their problem classes and because of the technical details of -Vn+ described below itís plausible that the approach works rather universally.
How is it done?
-Vn+ uses -Vn internally (-V0+eco uses -V0), but the accuracy demands for short blocks are increased. Short blocks are used when the encoder takes care of good temporal resolution. Audio data bitrate is kept rather high also with long blocks which are normally used.
These audio data requirements are helpful for any kind of problem, they are not restricted to ringing or pre-echo issues.
Moreover a strategy is used which is targeting at providing close to maximum possible audio data space for short blocks.
Whatís the price to pay?
Compared to -Vn the increased accuracy demands of -Vn+ raise average bitrate. As -Vn+ is targeting at significant quality improvements compared to -V2 for real bad samples, we need an average bitrate around 200 kbps at least.
-V3+ and -V2+ are designed for users of group b) above, and as such take care of average bitrate not to be much higher than 200 kbps. For my test set of various pop music average bitrate is 205 kbps for -V3+, and 217 kbps for -V2+.
For users of group c) I allow for the full quality resp. average bitrate range mp3 can offer.
-V1+ takes an average bitrate of 257 kbps for my test set, -V0+ takes 317 kbps.
-V0+eco (economic version of -V0+) takes 266 kbps. So -V0+eco comes nearly for free as -V0 takes 260 kbps for my test set.
Unlike versions I published before, mp3packer isnít really needed any more to squeeze the unused bits out of the mp3 file (with the exception of fractional settings like -V0.5+ between -V1+ and -V0+).
mp3packer brings average bitrate down by only 1 kbps maximum for -Vn+ between -V3+ and -V2+, by 1 to 2 kbps for -Vn+ between -V2+ and -V1+, and by 2 kbps for -V0+ and -V0+eco. So I think we can forget about mp3packer with these settings.
sets the minimum audio data bitrate for short blocks to x [kbps] when using -Vn+ or -V0+eco, with x in the range 150..450.
Defaults are 360,370,420,440,440 kbps for -V3+,-V2+,-V1+,-V0+eco,-V0+ resp.
sets the minimum audio data bitrate for long blocks to x [kbps] when using -Vn+ or -V0+eco, with x in the range 110..310.
Defaults are 160,170,215,220,290 kbps for -V3+,-V2+,-V1+,-V0+eco,-V0+ resp.
prints detailed information for each frame (L/R or M/S representation, blocktype of both granules, available audio data bits, audio data bits used, etc.). Works for both -Vn and -Vn+.
lame3100m -V1 --insane-factor 0.75
Oct 24 2012, 18:37
Joined: 22-July 12
Member No.: 101637
Halb, you mentioned that LAME 3.100 is in development right now - is Robert making that version available somewhere for testers? Based on the changes you've mentioned in that version, I wouldn't mind using it instead of 3.99.5 for ripping my old CDs, even if it is still being tested.
Regarding the "CBR idea" - it sounds like Robert is indeed developing that very idea. Let me try explaining it a different way to make sure. Essentially, I'm looking for an encoder that always provides the maximum possible accuracy, given the 320kbps restriction. Or, to put it a different way, a VBR whose accuracy requirement is continuously adjusted for each frame independently, until an accuracy requirement is found for each frame which fills every frame with 320kbps of data (or achieves 100% accuracy, whichever comes first). Theoretically, this would provide the best quality possible in a standard MP3.
To give a simple example, let's say that 5 long frames in a row would require 270, 280, 270, 290, 300kbps to achieve the -V0 quality (say, 95% accuracy). Reencoding those frames for 96% accuracy would require 290, 310, 290, 320, 320kbps. The last two frames would need to stay at 96% accuracy as they have capped, but the first three could be increased further - say, to 97% or even 98%. Short frames, the use of the bit reservoir, and dynamic adjustments to the lowpass/highpass filters on a frame-by-frame basis, would further complicate this.
Does that make sense?
I recognize that such an encoder would likely be very slow, but I would argue it'd be worth it. I'd even propose a new name for this method - something like DBR (dynamic bit rate).
This post has been edited by BFG: Oct 24 2012, 18:52
|Lo-Fi Version||Time is now: 31st October 2014 - 07:35|