Is This Lossy?

[graceadelica]

Got a number of bootlegs from a trader. The trader thought they were lossless, but when I ran it through the spectrum anylsis on Audacity it shows the frequencies dip, then come back up - as opposed to a straight descent. Anyone able to confirm whether this is the case or not? I'm no expert, but as far as I'm aware - even if it's from an cassette, the frequency line shouldn't go like that. I've got a number of recordings from various different sources - 70's U.S Radio, 70's and 90's audience recordings and they all have the same frequencing dipping going on.

Cheers

[ameyer17]

Hard to tell from that shot. To be conclusive, I'd need a spectral analysis.
I don't think that's straight-up lossy, though.
If I had to guess, lossy->analog transfer? It *could* also be 32 kHz DAT with some sort of noise shaping in the resampling algorithm.

[graceadelica]

Originally Posted by ameyer17

Hard to tell from that shot. To be conclusive, I'd need a spectral analysis.
I don't think that's straight-up lossy, though.
If I had to guess, lossy->analog transfer? It *could* also be 32 kHz DAT with some sort of noise shaping in the resampling algorithm.

Thanks for your reply. Could you please let me know how to do a spectral analysis in Audacity? I can only see how to do a spectrum analysis.
Considering the various sources, and the same wave pattern on all of them, I'd be surprised if was due to 32 khz DAT (I'm pretty sure DAT hasn't come into the lineage of any of them) - that wave pattern is unnatural though, isn't it?

[procella]

Wouldn't think this one is lossy. It drops but not really hard and it comes back also. Don't see anything pointing to a 32 khz DAT.

What you provided is a FA (Frequency analysis) - there is some mislabelling in audacity. But you should add a spectral, yes. Would show the reason for this clipping clearer, probably. Best, one shot of a complete song and a 2sec shot from this song. A discussion about tools for FA and SA is here: http://www.tradersden.org/forums/showthread.php?t=4288. I use Cool Edit Pro trial version. You can still use it for the spectrals after trial expires.

[Five]

for audacity spectral (aka spectrum) go in the preferences and set the maximum freq for that to 22050Hz (by default its at something like 8kHz, not useful for our purposes).

then go back to where the wav is, at the left there's a little triangle where you can switch it to spectral. take a screencap zoomed to 2 seconds and another zoomed to 1min or so then we can maybe get an idea what's going on with this one. strange highs there....

[graceadelica]

Thanks. Just attached 2 seconds & 1 minute zooms.

[Five]

okay from what I can see here, I think its lossless with a bell eq cut to the highs (presumably to reduce noise).

if you could put a 20 second or so FLAC sample or a very short song up on megaupload.com/rapidshare/similar I would like to take a closer look (most likely its okay imo)...

[graceadelica]

Just uploaded 30 sec clip here:

http://rapidshare.com/files/22636235...No03.flac.html

Thanks.

[Five]

thx... sorry for the delay

totally looks like eq cut on the highs, no sign of lossiness whatsoever that I can detect

[graceadelica]

Thanks - much appreciated!