Clipping in "HD" digital files

Question

I have a subscription to Amazon Music HD.

They allow downloads of music files in HD and ULTRA HD.

HD is defined as 44.1khz 16 bit - CD quality in other words.

Just out of interest, I though I'd have a go at recording the dowloaded files (encrypted and only playable through Amazon's app of course) into Audition and see how they compare to a mastered CD.

I'm using "what U hear" under MME driver on my Soundblaster E5, which is supposed to record the computer's audio stream.

I find that the signal level varies depending on how high I set the playback volume of the Amazon music app, so have been playing around with this.

Through trial and error, it seems the only way not to register clipping in audition's level meter is to set the app volume at 60 (100 being full).

The resulting waveform looks like this:

Certainly doesn't look like a mastered CD! I'm surprised to see the odd peaks, although they are very short and don't result in any audible peaks when listening.

If I record with the app volume at 100, I get something that at least looks right, except for the clipping:

The clipping I'm referring to is not audible when listening, just that it shows on the level meter and shows possibly clipped samples in the analysis panel, (although 0% clipped in Match loudness panel).

Obviously, if i hard limit the "clipped" recording (recorded at 100 level in the app) to -0.1db there's no problem.

Similarly, if I hard limit the non-clipped sample recorded at level 60 in the app to -3.1db (a ball-park estimation based on visual assessment of the moving peaks), then amplify by 3db, I get a file that looks very much like a mastered CD.

(Be interested to know if anyone has an opinion on which of the above would be the better approach)

Anyway... just thought I'd share this... mainly, I'm wondering why the clipping occurs - is it something to do with Amazon's app or something about the "what U hear" driver selection... or something else?

SteveG_AudioMasters_ · Answer

All bets are off when it comes to Amazon's app - we have absolutely no idea what it does, neither have we any idea of what processing may have been done to a signal before it gets to the app either. 'What you hear' generally works reasonably well - it's unlikely to be having any significant impact on the result. Except that you've got a Soundblaster, and there have been some significant sound issues with them in the past; doing A/B tests with them revealed clear sonic differences between them and many other devices, but in all honesty I don't think that's it.

The clipping is almost a different issue. For a start, you need to read some of the background to this, which is generally referred to as 'The Loudness War' - there's a Wikipedia page about this here and a search using the term will reveal plenty more. But in general now it's been 'fixed' (and I don't think in a particularly good way) by all of the streaming companies so that basically, everything sounds the same. There's an article about that here. In general though, what this means is that you don't see anything like as much of those clipped peaks as you used to, which does make me wonder exactly what Amazon are up to, and that's the thing - unless you have the actual CD release of a track, you won't really be able to judge exactly what's happening with the processed version.

In general, if you want to increase the overall level of something without introducing clipping, then you limit the peaks - we've been doing that for years. Once it's done though it's really difficult to undo, and it's rare for music tracks to be released looking like they've got a lot of spiky peaks in them. So really, more information is needed.

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