Recently I've encoded "Since I Left You" by The Avalanches, and I've noticed that LAME decides to use a very high number of 320kb frames (details below) when using --alt-preset extreme. I've got no problem with this, and I know the theory behind why this is (i.e. it's trying to achieve transparency) but purely out of interest I was wondering precisely what element(s) of the music LAME was finding hard to encode accurately. I know it's a slightly unusual question but this is a tech-MP3 forum, and I know how much some of you lot know aout MP3 and how it works... so I was hoping to gain some insight. I would also be interested to know if LAME achieves transparency with the track to some of the more trained ears here.

Another interesting thing which the developers might be interested in is the massive difference in average bitrate between standard and extreme (again, details below). Standard uses about twice as much scalefac_scale as Extreme. I don't think that's "normal", is it?

Obviously I do have the original track, but I've not got the webspace to host a flac... and I assume there would be some copyright issues there too? I would be happy to provide samples, anyway, if someone could point me in the direction of a webspace provider who allowed (fairly) large files to be uploaded for free...

Also, apologies if this thread is a bit "useless", but like I said above, it's mostly just to satisfy my own curiosity, and hopefully the unusual behaviour might be of some interest to the developers.

Details:

Encoded with LAME 3.92

Using --alt-preset extreme:


Using --alt-preset standard:

Hmmm, 100 views and no replies? Heh, I suppose it was silly to post a question specific to one track and not provide FLACs. Here are three of them, then... hopefully someone can satisfy my curiosity?


http://week.pwp.blueyonder.co.uk/sample1.flac

http://week.pwp.blueyonder.co.uk/sample2.flac

http://week.pwp.blueyonder.co.uk/sample3.flac

Maybe a lot of people are like me... they view because it sounds an interesting topic, but don't post because the answer is way above their head Or maybe I'm just dumb?

You're not alone!

Edit: gazzyk1ns, why are using --alt-preset extreme? I was told that if I wanted 320 kbps (check here), I should use --alt-preset insane. Is there a difference between the two?

Haha yeah, I know what you two mean... wish I knew the answer myself, then I wouldn't have to post the thread! Hopefully Dibrom, , Gabriel, mithrandir or Guruboolez might be kind enough to enlighten us...

Yeah, --ape produces a VBR file averaging around 256kbps, although that depends on how complex the music is to encode. --api produces a CBR 320 file.

That's kind of what I was interesting in finding out, i.e. what it is about the track which makes LAME feel the need to use so many 320 frames when using --ape, and also the large difference in between --ape and --aps with this particular piece of music.

Man I feel stupid >_< .
It was explained in the topic I linked to in my previous post. I just did not read it far enough because all I was looking for is best possible quality when encoding MP3s.

My guess (and it's just a guess) is that it pushes the bitrate so high because the track uses lots of samples from vinyl, with subtle BG noise and obvious clicks. Clicks are basically impulses - an mp3 weakness - ape is probably detecting some of these, and cranking the bitrate up to cope.

Also, the stereo effects in that track are quite extreme. The dominant sample has a chorus effect, and is mainly out-of-phase between the two channels. Convert the track to mono, and see how many effects and sounds vanish! The fact that Left, Right, Left+Right, and Left-Right are always so active and different means that many more bits are required for transparent encoding than on your typical pop tune.

This is just a guess - but I thought you'd appreciate some vaguely acurate info, instead of none at all!

Cheers,
David.
P.S. I like Since I Met You and Fronteer Psychiatry (sp?) very much - what's the rest of the album like?

Yes, thanks 2BDecided, the info was appreciated! The comment about the left and right channels being cery different does make sense, I notice that a "shaker" is almost continually active completely in one channel. I wasn' aware that clicks were tough for MP3 to handle though.

It's tough to say what the rest of the album is like - Since I Left You and Fronteir Psychiatrist are definately the best tracks, and to be honest I think they should have left some "fillers" off it... it's all mixed, and some of the tracks amble a little. Having said that, it depends what kind of mood you're in; I've listened to it all and been disappointed, and then another day completely changed my opinion of it. It's definately worth a listen, though.