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  #1  
Old 2015-06-03, 12:49 PM
OtherWeis OtherWeis is offline
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Possible MP3 in lineage?

I was about to seed a show that I received in a trade many years ago and have not seen on any trackers. I was running the usual Spectrograms and Frequency Analyses when I saw something I had never seen before (to be fair, I am not the most experienced when it comes to seeding). In the Frequency Analysis, it tapers off at around 15,000Hz (not a sharp drop), then seems to come back up at low level at the higher end. Here are couple of screen shots:




As far as I know, this was from a European Radio Broadcast. I am not sure how to interpret it. My (relatively uninformed) impression is that there was MP3 in the lineage, but somehow ended up being transferred to analog somewhere after (I received this in a trade almost 15 years ago, so this is not a completely ridiculous scenario). Can anyone else interpret these data for me?
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  #2  
Old 2015-06-04, 01:17 AM
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rspencer rspencer is offline
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Re: Possible MP3 in lineage?

The drop is likely the limitation of the recording equipment. It looks like plenty of lossless FM shows. Hard to tell here, but I'd bet that a close-up tight cut of the spectral (just a few secs) would look fine.
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  #3  
Old 2015-06-07, 02:38 AM
tdendonko tdendonko is offline
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Re: Possible MP3 in lineage?

That 15-16 KHz dropoff is typical of FM and analog TV broadcasts. If the source for this is an FM broadcast recorded off analog aerial reception (and not a pre-FM recording), then the 15 KHz dropoff makes perfect sense, all FM recordings look like this and there's no reason to suspect there was MP3 involved. You also seem to have a few spikes which go up over 16 KHz, and that wouldn't be there if it was a transcode from low-bitrate MP3. And only low-rate bitrate would have produced a ~15 KHz cutoff in the first place. So bottom line: I would attribute the way it looks to it being FM sourced, and definitely not to MP3 compression.

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Originally Posted by OtherWeis View Post
I was about to seed a show that I received in a trade many years ago and have not seen on any trackers. I was running the usual Spectrograms and Frequency Analyses when I saw something I had never seen before (to be fair, I am not the most experienced when it comes to seeding). In the Frequency Analysis, it tapers off at around 15,000Hz (not a sharp drop), then seems to come back up at low level at the higher end. Here are couple of screen shots:




As far as I know, this was from a European Radio Broadcast. I am not sure how to interpret it. My (relatively uninformed) impression is that there was MP3 in the lineage, but somehow ended up being transferred to analog somewhere after (I received this in a trade almost 15 years ago, so this is not a completely ridiculous scenario). Can anyone else interpret these data for me?
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