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Lossy or Lossless? Please use this forum to post spectral and frequency analysis posts about shows you have your doubts about.

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  #1  
Old 2005-11-29, 12:17 AM
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Is this lossy?

Hello to all,
I have just downloaded a SHN set of the Beatles' A/B road session but I'm really not sure it is pure lossless. Though I don't hear any gap between tracks when playing in foobar, I suspect it's mp3 sourced. I've attached my spec/freq results... Thanks in advance!
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File Type: gif freq-shn.gif
( 85.6 KB, 44 views)
 
File Type: gif spectral-shn.gif
( 177.5 KB, 38 views)
 
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  #2  
Old 2005-11-29, 10:25 AM
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Re: Is this lossy?

liveman...can you zoom the SA to ~2 secs...its hard to tell when zoomed out to the whole track...
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  #3  
Old 2005-11-29, 12:53 PM
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Re: Is this lossy?

Ok, here's a zoom of the spectral analysis:
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  #4  
Old 2005-11-29, 01:55 PM
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Re: Is this lossy?

thanks liveman...my impression is definitely lossy [don't know if its mp3 or some form of MD compression in the lineage?]...i'd let some of the others confirm this tho first
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  #5  
Old 2005-11-29, 04:34 PM
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Re: Is this lossy?

although it looks very much like lossy due to the absence of anything whatsoever above 14kHz, there are no blocks visible when zoomed in to 2 seconds.

there was much discussion about this last year at stg, especially vigotone's 30 Days release which was deemed lossless but heavily noise reduced. the purple chick set (by reputation) is a little less noise reduced, but still the nr is quite heavy.

another note about the early a/b road sets is that they were seeded in shn and since they are pretty much mono they compress down to 50% of the size if converted to flac. the conversion should be done using a secure method (see my signature).

I have three versions of these sessions (twickinham sessions box, 30 days, a/b road) and can pull them out and post screenshots from here if necessary. its quite a bulk of material (around 100 audio cdrs decompressed ). I plan to sort it all out and reseed/vine it somehow next year.

if you tell me the date/track of this a/b road session I can pull mine up and make sure that it looks the same as yours if you're still worried about it.
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Old 2005-11-29, 05:42 PM
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Re: Is this lossy?

Thank you AAR and Five for your replies I really appreciate it!

FIVE: The track I used for the screenshot above is from the January 23rd 1969 session, disc 1, track12. Files are SHN and presumably the same as:

--==<< Lossless Post Information >>==--
___________________________

Album Posted ============> The Beatles - AB-Road 1-23-69 Disc 1
Label & Catalog Number ==> Purple Chick
Number of Tracks ========> 27
___________________________

Name of Poster ==========> Hexer
Date Posted =============> 3/9/2004
Ripped Media ============> Original SHN files from Purple Chick
Program Used To Rip =====> Unknown
Number Of Discs Needed ==> 1
Posting Size ============> 332 Megs
Number of Files Posted ==> 29


Originally posted to a beatles newsgroup, the seeder told me he got the set from DIME some time ago...


Thanks again for your help!!!
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  #7  
Old 2005-11-30, 01:57 AM
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Re: Is this lossy?

Ok, I've decoded the SHN to WAV and then encode it to MP3 (vbr extreme, setting 0). Then I've decoded the MP3 to WAV and here's the spectral view. I think there is a very small difference with the scan I've posted above but I can't interpret it.

MP3 spectral view:
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  #8  
Old 2005-11-30, 03:10 AM
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Re: Is this lossy?

I don't have a sample but playing around with colours and contrast of the negative reveals blocks. A black/white picture would be helpful. Looks mp3 to me.
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  #9  
Old 2005-11-30, 01:24 PM
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Re: Is this lossy?

Hi range_hood, I've attached black & white spectral view from both files (1=shn>wav / 2=shn>wav>mp3>wav)
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File Type: gif speczoom-fromshn-b&w.gif
( 277.2 KB, 39 views)
 
File Type: gif speczoom-frommp3-b&w.gif
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  #10  
Old 2005-11-30, 01:49 PM
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Re: Is this lossy?

oh wow the plot thickens

both look lossy. you can't get those kind of block artifacts without lossy encoding. if anybody knows a way, show me how.

I'll break out my a/b road asap to see if it is the same as yours

could it be the entire a/b road is mp3-sourced??
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  #11  
Old 2005-11-30, 03:53 PM
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Re: Is this lossy?

Thank you again Five for your reply!
I'll stop downloading the set right now. By chance I've only downloaded the 23 January session and almost finished the 25th.
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  #12  
Old 2005-12-02, 07:31 AM
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Re: Is this lossy?

Quote:
Originally Posted by liveman
Ok, I've decoded the SHN to WAV and then encode it to MP3 (vbr extreme, setting 0). Then I've decoded the MP3 to WAV and here's the spectral view. I think there is a very small difference with the scan I've posted above but I can't interpret it.
MP3 encoding always changes the spectrum. The result of your procedure pretty much doesn't tell you anything.
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