Since last fall when I lambasted Amazon on my music blog for their piss-poor catalog of non-DRM'ed music for sale, they've improved a lot and their catalog is becoming more robust. Last night they had the majority of 1970's-00's pop and rock hits that they did NOT have in my earlier test.

That's the good news. The bad news is that the quality is very uneven. Most of the songs I downloaded are LAME 3.91 256 kbps MP3. Some of them sounded very good (as they should if that scheme is done right). Others sounded horrible, with the main culprit seeming to be the gross overcompression and clipping common to so many streaming internet "radio" stations these days.

Does anyone know if Amazon does their own in-house encoding, or do they get it from the labels, or do they outsource the work to some kid in Bangalore who does it in his bedroom while his parents think he's doing his homework? Why is it so inconsistent? There's no reason why a LAME-encoded 256 kbps MP3 shouldn't sound really good on every song.

In my experience, the sound quality has been very good from amazon. Could it be the source material rather than the encoding?

I don't know if they do all the encoding in-house, but they do have an mp3 team overseeing it all. Check out post #30 here. The conversation's not directly related to sound quality, but it is a response from someone at amazon who works on the mp3 library:
http://www.boingboing.net/2008/01/22/chall...figure-out.html

Amazon requires either WMA Lossless or FLAC from labels, then they encode themselves. I stick the quality differential on the labels, as I'm unconvinced that most labels have digital assets managers (or whatever respective title at each given one) that know enough about digital audio to rip and encode a master properly.

Note: I do not work for Amazon; I work for a label, and have plenty of experience dealing with, and complaining about, Amazon.

From the label side, what complaints do you have? Just curious.

If the source is lossless and they encode to mp3 256 kbps (using Lame), how on earth do they manage to get it wrong? (all I can think of is some kind of volume normalize).

I know that Amazon uses different versions of Lame at different settings. I purchased Disturbed's Inside The Fire single and it was encoded at 256kbps CBR using Lame 3.91.3 (I think it was x.xx.3 but I am not 100% sure, I will have to look at it again). I then purchased a remix of a Lacuna Coil song using my Pepsi Points and it was encoded at -V 0 --vbr-new using Lame 3.97. I also purchased another song not too long ago and it was encoded with Lame 3.97 as 256kbps ABR. So I am not sure what standards they use for mp3 encoding but it seems to be mixed.

I still haven't had any issues with sound quality though, even the Lame 3.91 song. I don't have the lossless version (yet) to compare it with but it sounds fine to be comparing it to the 128kbps AAC iTunes release.

First of all, Amazon's MP3 encoding appears to be nonuniform, as kornchild pointed out. I've gotten both LAME 3.97 V0 files and FHG 256kbps CBR files from them. That's no surprise though, eMusic's catalog has FHG CBR (192+kbps) and VBR LAME MP3s also.

BUT

I have no complaints whatsoever about quality.

Wow, so Amazon even uses a different mp3 encoder. It shouldn't really matter at such high bitrates but that is still interesting.

plnelson, can you provide some examples of what you're talking about here? It will help identify if the problem is the encoding or the source (someone may have the CD for comparison).

Have you checked the LAME version against the original CD. I mean LAME can't do wonders with poor mastering (?)...

The hoops you have to jump through in the media delivery, along with their rigorous authentification/ingestion process, are a bit more tedious than other current digital retailers.

Yeah, that's the problem with buying music online - I can't A-B it with the original. If I rip one of my own CD's and I don't like the way it sounds I can compare it to see where the problem is. I'll see if I can get some of these out of the public library consortium and check it.

In fairness to Amazon, I bought another dozen or so songs last night and in general the quality is quite high - just the occasional clunker.



One example that comes to mind is the copy of "Wicked Game" (Remastered Album Version) from the "Best of Chris Issak" album. It's got his vocals with a bass guitar (or stand-up bass? I'm not sure) Not only does the bass create a thumpy distortion, but sometimes when it appears with the vocals it distorts the vocals. When I looked at it in an MP3 editor, all the places where the distortion occurred were at 100% - totally clipped with flat-top peaks.

As expected, it's probably someone at a label converting a lossy format to FLAC or WMA Lossless for delivery on account of not-knowing-what-they're-doing.

What editor? Maybe it just can't decode mp3 files to 32-bit float to avoid clipping.

I'll see which one it was when I get back home (I'm at work now) but the problem is that the effect is annoyingly audible on my iPod 80G (using ER6i earbuds, which are not exactly known for exaggerated bass). If I back off on the already-weak bass in the EQ I can minimize the problem, but most tracks sound fine so I hate to do that just to accomodate a few marginal tracks.


But anyway, my point in starting this thread was to ask who does the encoding so I could understand the source of the inconsistencies and it appears that we're not sure. I don't want to go down a technical rat-hole - I'm writing an entry in my music blog on Amazon's MP3 offerings and I want to provide appropriate background information if I can find it.

I've purchased over 1GB of MP3's from Amazon, most 90's - 2000's era, but some from 80's and a few from the 70's. All have had excellent quality.