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View Full Version : Lossy vs. FM vs. cassette?


terabyte23
2008-10-13, 02:02 AM
Hi folks,

I received several trade CDRs with no source info, and I am trying to determine whether they are lossy. I suspect they came from a mix of sources (AUD > cassette, FM > cassette, FM > digital) but I am not certain. I am using EAC.

I am really interested in the differences between FM and lossy recordings - I find it confusing to determine whether an FM-sourced show appears lossy in FA and SA charts.

I attached a couple of examples generated from EAC. Thanks for any advice.

--t23

terabyte23
2008-10-13, 02:06 AM
And here are a couple more. These look more like mp3-sourced to me than the last examples. But I dunno! Do FM-sourced recordings ever look like this? Thanks.

SundayDriver
2008-10-13, 02:29 AM
If it's an old FM broadcast recorded to a tape, no, it's not going to show signs of data loss in a frequency analysis. Most FM broadcasts today are sourced from digital crap that will show signs of data loss through a frequency analysis though.

ameyer17
2008-10-13, 08:48 AM
Believe it or not, I think that both recordings could be FM-sourced.
You can see where it looks like the 19 khz pilot tone was filtered out.

FM recordings will show signs of frequency loss, period. They won't have anything above 15 khz except for noise and a 19 khz pilot tone.

SundayDriver
2008-10-13, 11:26 AM
They won't have anything above 15 khz except for noise and a 19 khz pilot tone.

Sure, but that noise will make a spectral and frequency analysis look more full than it really is. You won't see an obvious cut-off like you would see in an mp3 file.

procella
2008-10-14, 10:56 AM
Hi folks,

I received several trade CDRs with no source info, and I am trying to determine whether they are lossy. I suspect they came from a mix of sources (AUD > cassette, FM > cassette, FM > digital) but I am not certain. I am using EAC.

I am really interested in the differences between FM and lossy recordings - I find it confusing to determine whether an FM-sourced show appears lossy in FA and SA charts.

I attached a couple of examples generated from EAC. Thanks for any advice.

--t23

Most modern FMs are in fact lossy. They cut hard between 15 and 16 khz, usually. But if it is that hard CO only they are regarded as tradeable. Just like 32 khz DATs. There is no damage below CO.
You should provide a 2sec SA pic also. Shows bad structures much better. But from what you provided: First one has those typical MD structures above CO. And it is not a good one. Cuts below 14 khz. Second one smells like lossy. But, at least I, would need a 2sec SA to be sure about that.
Both don't look like FMs. No 19 khz carrier visible. But not all FMs show this stripe. The second isn't one, almost surely. Cuts above 17 khz. FMs don't cut higher than 16 khz.

terabyte23
2008-10-19, 01:18 AM
Thanks for all the replies. I attached two 3-second SA images.

terabyte23
2008-10-19, 01:38 AM
I am working with another set of recordings and found some weird ones (weird to me, anyway). Anyone know what these are? See attached images - check out the line at 16KHz in the SA diagram.

Actually it looks like I can only attach 3 images per post, so I will split this across two posts. Here are the first two...

terabyte23
2008-10-19, 01:40 AM
And here is another set. Check out the curves above 18 KHz in the FA. Thanks for any help!

procella
2008-10-22, 07:26 PM
Thanks for all the replies. I attached two 3-second SA images.

1996 show is lossy. Skyline has a few cuts and some irregularities above.
The other one is a MD, though not a good one. But when it was recorded that way it is tradeable.

I am only able to say a few things about the new ones. Hope one of the experts discovers them soon.

TVs have the stripe at 15.8 khz and FMs at 19 khz. But there are also stripes which aren't from the transmission. So, this doesn't tell much.

The second new one is a MD again. Doesn't have much damage below 16 khz, it seems. So this is a rather good one. FA really looks strange above 18 khz. But I am not familiar with those kind of FA pics, unfortunately.

Five
2008-10-23, 08:07 PM
everything you've posted so far looks lossy from what I can see ... some is minidisc, compare here:
http://www.thetradersden.org/forums/showthread.php?t=8003

its true, modern FM is 99% lossy but not like these pics you're showing. it cuts off much more abruptly.