Modern Day FMs

[GRC]

Again, I say; what's your point?

Whether you decide FM is lossy or not, in the absence of a better source, it's all you've got.

All FM broadcasts are 'off-air', 'over the air', or, for want of a better word, 'Post-FM'.

The only way to improve on it, without re-engineering the transmission protocols, is for someone to provide a matching 'Pre-FM' source. In the absence of this, does it really matter whether or not the post-FM is lossy or not? It's the ONLY source.

Regards, Graham

[Five]

Graham, its just a discussion with lots of techno and babble

[Five]

ps there's another thread over here:
http://www.thetradersden.org/forums/...ead.php?t=9766

I haven't found blocks in those samples other than the incredibly flat tops. Sound is quite good, better than the sound of the big stations in Toronto.

[procella]

Originally Posted by GIGFY26

Thanks for the info Five,

Did a quick google of some products and it does I see things like FM transmitter ranges of 20hz to 15 khz for the Orbands. I have to say that's surprising and a little disappointing. I always thought FM was a higher quality. I would guess and hope however that most stations run compression and not clippers. This would make it so the ratio from quiet to loud would stay intact but reduced and not just throwing info away. I'm not sure that would make a difference but it would make me feel better . I checked a few "FM" sources that I have for shows. For some reason EAC would only give me SAs of two and they fell of about 15khz but didn't seem as sharp as I have seen in some mp3s. The one that I could do a FA and SA, the SA still showed a dropoff around 15khz but the FA didn't show any sharp drop off. That seems a little weird.

Thanks guys. I hope we get a bunch of comments. I'm really trying to figure this all out as well, but I do feel it's a bit of a "guesstimate" sometimes. Again, that's where lineage can help so much to point us in the right direction.

Great Topic!!!!

Thanks for your explanations. A little background information is good always.

EAC isn't good. For SA you should get yourself CEP. Trial version is enough. FA and SA still work after it's expired. Check here:
http://www.thetradersden.org/forums/...ead.php?t=4288. I like audacity for FA, at the moment. That's pretty fine for my inexperienced eyes.

You can't decide what it is if you only know the point of the cutoff. There are also mp3s which only cutoff above 20Khz, MDs which cutoff below 16 Khz etc. And it may also have been compressed, pitch changed etc.

I think that a pro will be able to decide correctly in most cases. Basically the problem is that you only may proof lossyness but never losslessness. So that's like in science. You can only proof what's wrong. And the art is to find the right test in difficult cases which proofs lossyness.

[procella]

Originally Posted by Five

ps there's another thread over here:
http://www.thetradersden.org/forums/...ead.php?t=9766

I haven't found blocks in those samples other than the incredibly flat tops. Sound is quite good, better than the sound of the big stations in Toronto.

I know this one. But you didn't explain there why it is lossy. I was thinking about the cutoff at 15 Khz and the sharp cutoff line. But I couldn't be sure that's correct and that's all. So, please, a few words about its lossyness.

[Five]

well let me dig up some of my FM-sourced shows when I get home and get back to you on that... iirc the older FM broadcasts have a more hazy cutoff, but the new ones look like they've been very abruptly sawed off. In the case of these two broadcasts I couldn't find blocks and they sound decent, so maybe they're not lossy, perhaps they are using a more accurate digital LPF I'm not 100% certain, either. However there are other recent FM captures that I am certain about and I can post some SA screencaps from those, as well as some older FM shows from the pre-mp3 days and we can compare.

[Five]

I'm not even certain why they are lossy encoding broadcasts before sending them to air... here's a bit of relevant recent conversation from the zep board:

Originally Posted by Five

audio is really suffering these days... it seems like mostly every hifi cd that's sold doesn't get played, only ripped to mp3 and put on a computer and/or iPod. Its like you're totally out of fashion and a very strange person if you don't listen strictly to mp3/aac as your only source of music. Almost all the radio stations are broadcasting it now as well, which I don't understand. Are they short on HD space or something? I mean the analog broadcasts, of course it has an advantage for xfm

Originally Posted by SIBLY

You aren't saying XM or Sirius broadcast CD quality are you? Because there is no way they are.

Originally Posted by Five

no I'm saying that since its digital information being sent on XM/Sirius etc the lossy compression allows them to send 1000 stations, which is a tradeoff which you get something for.

what doesn't make sense is that the mainstream local stations are broadcasting the same way they did in the old days, but sending out lossy audio. Some stations in Toronto are worse than others... Q107, which is the Toronto classic rock station sounds like 128kbps cbr mp3, but its just an analog broadcast like it was back in the 80s when it didn't have all that mp3 swish in it. Now I'm listening to mp3s on my same reciever but no extra 1,000 stations wtf

Originally Posted by Dantheman

That was the product of Clear Channel/Infinity/and others.....they made every damn rock station in the country have the same lame 40 song playlist....thus taking a DJ and turning him/her into nothing more than an on air personality to lead in songs and repert PSA's and weather. The rest became automated and what easier/more efficiant way than have a computer do it.

[procella]

Originally Posted by Five

well let me dig up some of my FM-sourced shows when I get home and get back to you on that... iirc the older FM broadcasts have a more hazy cutoff, but the new ones look like they've been very abruptly sawed off. In the case of these two broadcasts I couldn't find blocks and they sound decent, so maybe they're not lossy, perhaps they are using a more accurate digital LPF I'm not 100% certain, either. However there are other recent FM captures that I am certain about and I can post some SA screencaps from those, as well as some older FM shows from the pre-mp3 days and we can compare.

Thought I try to google a little:

May 4 2005, 16:37 Post #51

The BBC distribute FM around the country in NICAM format, so assuming you can receive a relatively strong FM signal then you're basically hearing NICAM-encoded audio.

NICAM is 14-bit PCM companded to 10-bits using a sampling frequency of 32 kHz (see http://tallyho.bc.nu/~steve/nicam.html). So, not capable of CD-quality, but not too far off it. And although it might appear that its audio bandwidth will be narrower than MPEG audio because of the lower sampling frequency, all digital radio stations in the UK that I'm aware of lowpass filter with a cutoff frequency of about 15.5 KHz anyway, so there's really no difference in that respect.


Not sure if you know about that. 2 years old but NICAM should be a good guess still.

[Five]

well I'll be... so its a lower sampling frequency LPCM WAV?!?? that makes a hell of a lot of sense. Also slightly more shallow bit depth making it a little more coarse. Sampling at 32kHz gives a hell of an abrupt cutoff at 16kHz (nyquist). So its not mp3 at all!

The lower-grade wav doesn't make the hated swish, that's a hell of a broadcasting system they've got over there. Are you living in the UK? You should be thankful for the BBC

Source: WWOZ 90.7 FM New Orleans April 27, 2007
the third is a closeup (note frequency scale on right)

[procella]

I found a page about KCMP. Also over 2 years old. And there someone says that 'The actual broadcast signal quality is roughly equivilant to 96Kbps MP3'. But can't really confirm that this is correct.
It's almost funny. They search for music for their music library in CD quality and a person says: 'there is a quality issue with taking audio that has previously been compressed and putting it on the air. It really wouldn't sound all that great after passing through our web encoders or the digital radio codec'.

[Five]

^that one the DJ says was taped a couple days previous, perhaps delayed broadcasts are stored as lossy?

LOVE BATTERY @ HIGH DIVE - SEATTLE,WA. 2006-07-01 KEXP FM

[Five]

^Lineage: KEXP.org Lossless Stream
(codec of the stream is WMA Lossless - Original bit rate is 1411.2 kb/s.)
Total Recorder-WAV-Wave Splitter-TradersLittleHelper-FLAC(6).

it is not WMA lossless! oh, well. it sounds as awful as it looks, but its the first love battery show ever to be seeded (pretty sure).

[Five]

Originally Posted by procella

I found a page about KCMP. Also over 2 years old. And there someone says that 'The actual broadcast signal quality is roughly equivilant to 96Kbps MP3'. But can't really confirm that this is correct.

yeah, that's about right try encoding a 96kbps vbr mp3 and it will look about equal in quality to that, and a bit of a different 'signature' made from smaller blocks. I wonder what that codec is that they're using? looks a bit like minidisc type-r at the top

Originally Posted by procella

It's almost funny. They search for music for their music library in CD quality and a person says: 'there is a quality issue with taking audio that has previously been compressed and putting it on the air. It really wouldn't sound all that great after passing through our web encoders or the digital radio codec'.

they have strict control over transcodes... arrgh, its like oink or something.

they used to broadcast records on the radio, with no digital shit in the path, those were the days.

here's some from a talk radio show called Hour 25, scifi/comics talk radio 1986:

[Five]

^check out the soft cutoff on that!

[Five]

Taj Mahal New Orleans Jazz Festival 2007