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Nightwish - Angels Fall First
shadowking
post Jun 4 2007, 17:11
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Serious problems for LAME mp3 , similar issues with AAC.

This post has been edited by shadowking: Jun 4 2007, 17:23


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halb27
post Sep 8 2012, 20:33
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Thanks for that. Hopefully you will continue your valuable testing with my next regular version.
Unfortunately your version is just a premature version of 3.99.5y (with welcome side effects in this very context), and I am not able to reconstruct the internal details of this very version. Which is not as bad as it sounds, as I know about the potential ingredients. The correct version BTW can be downloaded from the 3.99.5y thread now.

One thing however is pretty sure right now: In order to have my extension improve things with problem cases like these, a relatively large increase in average bitrate is necessary for the low quality settings. According to first trials last night this makes sense to me according to the fact that usually everything is encoded fine even with a quality setting like -V5. With problem cases like this increasing quality level helps only in a way that is a bit disappointing. Increasing average bitrate with the defensive details of the functional extension seems to have a more stringent effect. Which is to be shown yet, resp. the exact details have to be worked out.

This post has been edited by halb27: Sep 8 2012, 20:35


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lame3100m -V1 --insane-factor 0.75
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Dynamic
post Sep 9 2012, 10:04
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QUOTE (halb27 @ Sep 8 2012, 20:33) *
One thing however is pretty sure right now: In order to have my extension improve things with problem cases like these, a relatively large increase in average bitrate is necessary for the low quality settings. According to first trials last night this makes sense to me according to the fact that usually everything is encoded fine even with a quality setting like -V5.


I'm keen to keep testing, so long as I have the time, which is a little sporadic at the moment. At least I'm familiar with what to listen for in this sample and I might give some like eig and herding-calls a go too.

I guess with about 83% of the files being long blocks and -V5 normally being about 130 kbps, and using about 480kbps for those short and switching blocks (320 + 50% of 320), a rough figure would be roughly 0.83 * 130 kbps + (1-0.83) * 480kbps = 190 kbps (7% - 10% short blocks respectively) after mp3packer. Perhaps that's a slight overestimate based on my actual results, so maybe it's not right up to 480 kbps on all short block or on the switching blocks.

I suppose that's still better than going to -V2 and still having an artifact, albeit more subtle when you've identified the problem sample. I guess it's possible to have a -V n- mode that employs somewhat lower short-block minimum bitrate or a lesser increase in the requested Signal To Mask Ratio (or quantization error). Hmm. Maybe my "volume of soil to cover seeds" analogy isn't so far off in numerical proportions.

I guess we could say that compared to -V5 with artifact,
-V0+ requires about 150-180 kbps of bitrate increase in this specific case, but sounds perfect
-V0 requires about 130 kbps of bitrate increase but sounds near enough OK, maybe a subtle artifact
-V2 requires about 50-60 kbps of bitrate increase and still has an artifact, slightly less than -V5
-V5+ requires about 40-55 kbps of bitrate increase but sounds essentially perfect (to my limited ears).
-V6.3+ also requires 40-55 kbps of bitrate increase (i.e. little to no bitrate advantage) and sounds fine to my ears

I wonder if I might be able to think of a reasonably efficient algorithm and threshold to detect tonal components within short blocks (if that is indeed the problem with this class of artifacts), perhaps by comparing samples like this to samples with spectrally-white transients like the Dave Matthews Band sample 4_40_30sec or whatever it's called and perhaps version 3.97 to version 3.99 in samples where they differ in this sort of artifact.

I remember some years ago (3.90.2 era, perhaps) playing with lamex (I think that was the name) which produced graphs of the waveforms and spectrum of original and reconstructed signals. I don't know if there's still a compile switch to create a lamex based on 3.99.5x or y. I don't tend to look as I haven't had a C compiler installed in years.

I'd have thought there might be an algorithmic way to pick something out and set an appropriate detection threshold for maximizing bitrate in this sort of sample but not in more normal atonal short block transients. This would probably greatly reduce the bitrate increase (after running mp3packer or implementing a method of building up maximum bit reservoir within LAME only where it's about to be needed).

-V5+ plus short-block tonality threshold might (guesswork) require anything between 10 and 30 kbps more bitrate, perhaps 5-20 kbps on a whole collection (after mp3packer or backward bit-reservoir accumulation)

Or, more sophisticated than a threshold to request maximum bitrate, setting a better fitting function rule for requesting a progressively lower quantization noise (or SMR) as some measure of relative tonality increases, either using the existing analysis functions such as FFTs used by the psymodel or maybe comparing additional FFTs of various lengths (which could be active only during the analysis of short blocks, limiting the encode-speed reduction). A potential problem with relying on the internal short-block detection and switching before even looking for tonality would be if in future versions of LAME, the detection threshold were modified, breaking any change we make to solve this sort of problem or unmasking some edge-cases.

I expect I could generate some artificial test tone + transient samples or mix a pair of percussive and tonal tracks over a range of relative loudnesses in some sort of Design Of Experiments style to try to plot out where the limits of audibility lie.

Thanks again for the time and effort you put in, Horst.

Ryan.


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Posts in this topic
- shadowking   Nightwish - Angels Fall First   Jun 4 2007, 17:11
- - odyssey   Please add version, parameters etc. I had no prob...   Jun 4 2007, 17:18
- - shadowking   I first spotted it with 3.97 ages ago. Tested 3.98...   Jun 4 2007, 17:26
- - greynol   I'm not sure I could ABX at -V3, but at -V4 di...   Jun 4 2007, 17:35
- - halb27   Tried 3.97V5 on it. I couldn't hear the proble...   Jun 4 2007, 19:52
|- - shadowking   QUOTE (halb27 @ Jun 5 2007, 04:52) Tried ...   Jun 10 2007, 04:33
|- - LANjackal   QUOTE (shadowking @ Jun 9 2007, 23:33) QU...   Jun 10 2007, 18:43
- - LANjackal   For what it's worth, I couldn't ABX it at ...   Jun 5 2007, 06:53
- - stigc   It's funny, Vorbis (aoTuVb5) have no 'trem...   Jun 5 2007, 11:11
|- - Pio2001   QUOTE (stigc @ Jun 5 2007, 12:11) Does an...   Jun 8 2007, 00:18
- - Jillian   Out Of Topic. I'm very disappoint Anette, ne...   Jun 5 2007, 11:26
- - robert   @shadowking: nice sample, but I think we cannot fi...   Jun 7 2007, 14:26
- - alter4   I was able to abx even lame 3.99.5 with -b320 -q0 ...   Sep 4 2012, 11:05
|- - halb27   QUOTE (alter4 @ Sep 4 2012, 12:05) I was ...   Sep 6 2012, 20:29
|- - IgorC   QUOTE (halb27 @ Sep 6 2012, 16:29) You us...   Sep 8 2012, 04:13
|- - MostlyHarmless   QUOTE (IgorC @ Sep 8 2012, 06:13) p = 0.0...   Sep 8 2012, 12:12
|- - C.R.Helmrich   0.5^number-of-trials. Igor, I wouldn't say 5 i...   Sep 8 2012, 13:17
- - psycho   I missed this thread in 2007, but now I'm inte...   Sep 4 2012, 16:47
- - lvqcl   05___Angels_Fall_First_ringing.flac was (re)upload...   Sep 4 2012, 18:15
- - psycho   Hm, I can't hear it... I've tried -V 6 to ...   Sep 5 2012, 19:38
- - mixminus1   A ringing/fluttering in the right-channel guitar, ...   Sep 5 2012, 20:13
- - psycho   Thanks, mixminus1. I will try it again tonight. B...   Sep 6 2012, 11:33
|- - Dynamic   I wanted to try out the VBR+ mode (-V n+) of halb2...   Sep 6 2012, 18:59
- - psycho   Aha! Now I took time, put my headphones on and...   Sep 6 2012, 17:19
- - halb27   Thank you for applauding 3.99.5y, but I'm afra...   Sep 6 2012, 20:17
|- - Dynamic   QUOTE (halb27 @ Sep 6 2012, 20:17) Thank ...   Sep 8 2012, 17:29
|- - halb27   QUOTE (Dynamic @ Sep 8 2012, 18:29) That...   Sep 8 2012, 18:54
|- - Dynamic   QUOTE (halb27 @ Sep 8 2012, 18:54) Anyway...   Sep 8 2012, 20:02
- - halb27   I tried various 3.99.5 -Vn settings with this inte...   Sep 7 2012, 21:49
- - alter4   QUOTE (halb27 @ Sep 6 2012, 22:29) QUOTE ...   Sep 8 2012, 11:14
|- - halb27   QUOTE (alter4 @ Sep 8 2012, 12:14) I did ...   Sep 8 2012, 18:28
- - halb27   Thanks for that. Hopefully you will continue your ...   Sep 8 2012, 20:33
|- - Dynamic   QUOTE (halb27 @ Sep 8 2012, 20:33) One th...   Sep 9 2012, 10:04
- - alter4   Guys, just one question. What is LAME3.99y encoder...   Sep 9 2012, 11:14
- - halb27   You can download it from the 3.99.5y thread. Than...   Sep 9 2012, 13:30
|- - Dynamic   QUOTE (halb27 @ Sep 9 2012, 13:30) You ca...   Sep 10 2012, 17:34
- - halb27   Here comes a candidate for 3.99.5z to play with. T...   Sep 10 2012, 22:16
|- - Dynamic   Thanks, I look forward to testing this. Ryan. [e...   Sep 11 2012, 08:40
|- - halb27   QUOTE (Dynamic @ Sep 11 2012, 09:40) ... ...   Sep 11 2012, 09:23
- - halb27   I'd like to draw special attention to the samp...   Sep 11 2012, 09:09


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