Radio Transmission 'Quality'

Johnboy1951

What is the view, generally, about the 'quality' (true to source) of the received Radio signals of the various methods we are familiar with ........ radio on Saorview; DAB; DAB+; FM ?

I realise there are bandwidth issues and different methods of transmission and of encoding ......... but to the end user all that is hardly of interest ....... what is most important, I imagine, is how true to source is the received signal after decoding/whatever.

I don't have a DAB(+) receiver .... and it seems likely I won't as long as FM is transmitted ..... but am interested in information about the 'end result' of the various methods.

Thanks for any info/comment

watty

The biggest issue is the destruction of quality by the over use of processing in the Station.

Quality on DAB can be similar to a good FM signal. It's not going to equal CD. Most Digital transmissions are now at too low a bit rate. You need 256k MP2 on Satellite, DTT or DAB for Near FM quality.

If you have a good signal, then FM can be excellent. If it was fed with unprocessed audio.

So the biggest issues are:
1) Station quality. Most are too processed to make them seem louder.
2) FM you need a good signal for Stereo, less signal can be fine for Mono.
3) Minimum acceptable MP2 is 192k, 256K would be better. DAB, DTT and Satellite use MP2. DAB+ and Saorview can use AAC which makes 128K sound like 192K MP2.

Satellite used to be all 256K audio, seems to be a mix of 128K and 192K now. Some of the RTE on DAB and Saorview are only 128K.

If you over process in Station, then it doesn't make much difference if the Transmission is 128K or 256K.

It's crazy that now your own CD rips @ 256K VBR MP3 (256K MP3 is slightly poorer than 256K AAC and a lot better than 256K MP2) on a phone with €9 earphones sound far better than FM, DAB, DTT or Satellilte.

Johnboy1951

I notice Saorview audio on TV channels is

BR:192Kb/s SR:48KHz mpga (mpeg 1 layer 2 I believe)


while the radio stations carried on Saorview, including LyricFM are

BR:128Kb/s SR:48KHz mpga

... seems counter to what I would have expected ...

I have also noticed that quite a number of internet stations are using AAC+, but are apparently limited to 64Kb/s (or any I have come across are).

I have no idea what our DAB stations are doing .... nor indeed what is available via Astra Satellite or what Saorsat will deliver.

I will say though, that I believe that CDs themselves were (are?) over-processed, so they can hardly be held up as a model.

It would be nice to know what to expect from each of these technologies, and not be just fobbed off with "digital" as if it were meaningful.

It would appear that regardless of source, we are getting a much reduced 'quality' over the 'digital' airwaves than we have a right to expect.

crosstownk

I'm no guru on FM vs DAB so all I can offer is my opinion based on what my ears pick up.

FM: FM is fine and I see no need to change from it (aside from potential bandwidth issues). I like the sound from FM despite the fact that some stations have some background noise. I also hear more interference on FM but it's hardly an issue and most likely due to local grounding issues.

DAB: I have a DAB receiver and find the sound a bit more 'civilized'. Less noise and the use of studio compression more effective - exactly what I'd expect from digital. What annoys me is the signal drop out - this might be down to my location or antenna but I get the odd drop every now and then. My DAB receiver only offers the RTÉ stations so I can only base my listening experience on the RTÉ feeds. Higher volume on DAB is much, much cleaner - less clip is the most obvious. I haven't scanned for new stations recently but I'd like to have more choice.

watty

DAB is mpga (mpeg 1 layer 2) = MP2, only DAB+ can optionally use AAC.
Saorview currently is only using MP2 but can use AAC. Likely it will only use AAC either for 5.1 on TV or to save bit rate at the same quality.

64kbps AAC is poor, but it would be worse if MP3 and MUCH worse if MP2 (= Mpeg1 Layer 2)

I have have noise free FM reception on at least RTE1, 2FM, Lyric, Mid West Hospital Radio, Clare FM, Limerick 95, TnaG, Spin South West, Today FM and if I use roof aerial Tipp and Kerry.

The RTE Additional stations on Saorview sound poor to me.

I haven't seen ANY standalone DAB radio that isn't easily outperformed on quality by decent 1980s AM/FM portables and even my 1947 Every Ready "Personal" B outperforms most DAB sets in battery life.

The Coverage in N.I. isn't good enough for DAB. My brother in law has reverted to FM only on his Car radio citing poor coverage and slow to change channel. He asked me what was the point of DAB?

But the biggest issue is the over-compression and over processing (common to DAB/Saorview/Satellite and FM). Such that on ALL my FM sets my own MP3s sound better via a €6 FM Transmitter gadget (aka "iTrip" except I have no "iThings").

My son's BD Hometheatre player/Amp has an FM Radio. It also is limited by the rubbish quality of the Studio/Station output, not by the FM Technology.

DAB has ONLY an advantage over FM if your FM signal is bad and the DAB signal is good. A decent 75cm whip fixes that on a car.

Saorsat is a subset of Saorview at same quality, nothing extra.

There are about 2000 FTA satellite Radio stations if you have a Motorised dish. Most of the useful ones are on 28E, 19E and 13E. Veronica, Swiss and French Jazz, etc.

crosstownk

watty wrote: »

DAB has ONLY an advantage over FM if your FM signal is bad and the DAB signal is good. A decent 75cm whip fixes that on a car.

Saorsat is a subset of Saorview at same quality, nothing extra.

There are about 2000 FTA satellite Radio stations if you have a Motorised dish. Most of the useful ones are on 28E, 19E and 13E. Veronica, Swiss and French Jazz, etc.

You may have inadvertently pointed to something here. My DAB receiver (also FM, iPod, CD, Aux) has a long wire as a DAB antenna and nothing as an FM antenna. Maybe I need to at least have my FM antenna equal my DAB antenna.

I'm using terrestrial DAB rather that Saorview (but I'm sure the transmission medium is similar if not identical) so I'm limited to what's available out of the air around me.

STB

Jeez Watty the FM Engineers in your part of the country will be saddened to hear of your listening experiences.

FM stations whilst processed to feck doesn't use compressed sources. Any FM station worth its while will be using raw WAV files from its playout library. Optimod/Orban sound processing is normally added to the chain prior to transmission to give it whatever shape the stations desire, most music stations I have heard around the country are loud and punchy, whilst some not so much or borderline flat presumably so as to not tire the listener.

In my experience, everyone thinks they are a sound engineer! Your Itrip little FM exciter thingy, if for example you where outputting that from a laptop, I would recommend you try out the likes of BPM. Its a five band processor. Sounds lovely, you will never look back to original source!

Everything else DAB/DTT etc involves serious compression and shouldn't be used as a comparison. AFAIK, DAB+ was being used under that research licence in South East and that some of those stations were 48k. Most of the DAB output were 128k, except for Nova and 4 which were 160. A mixture of FM and Net feeds.

watty

No station should EVER be "loud and Punchy". It's a gross crime against quality and makes their care of Source ironic.

We need to distinguish between Compression in two senses.
The old sense of reducing dynamic range is better now called "Processing". It's a great evil today. It should only be an option built into car radios and removed totally from the Stations.

The Modern Sense of Compression is "bit rate reduction". This is the use of "lossy codecs".

More frequency response needs more Bit rate.
More dynamic range needs more bit rate
More Channels i.e. Mono, joint Stereo, 2 channel, 4 channel, 5.1 channel
There are three Codecs used commonly with Audio for Bit Rate Reduction (Data Compression).
MP2 (really old)
MP3
AAC (DAB+, DRM. Streaming, MPEG4 systems Audio etc).
Note that at higher bit rates there isn't much difference. But at lower bit rates that are sub FM Radio quality (when you have a good un-processed signal) then for same quality MP3 lets you have lower bit rate (more compression) and AAC much more, for similar subjective quality.

At 256K there isn't a huge difference. At 128K AAC is best and MP2 is very poor. MP3 is sub par at 128K.

I don't think I'm a Sound Engineer. I worked in BBC, AV facilities company and then on Digital Telecomms. I'm a Communications Engineer, Sound Engineers are not experts in Processing and Bitrate reduction. If they are properly trained then they might operate the gear. I can design it. Good Sound Engineers know the difference between a PPM and VU meter and know well how to relate both to the Program content so that the level is correct.

FM can be HiFi
DAB, DAB+, Satellite or DTT can be close to HiFi.
At sensible bit rates the Codec isn't so important. AAC is most of value for LW/MW/SW AM replacement low bit rate. It's crazy the greed on DAB/UHF/Satellite spectrum to "fit more channels" and less bit rate. DAB is only a 1.7MHz chunk per Mux of the 100MHz of Band III. Why not have more multiplexes and 256k. The effort to do 48k on VHF is greed.

Similarly cutting back Satellite Radio that used to be 256K to 128K MP2 is greed.

IMO Music or Speech on Radio ought to sound just as if it's a CD playing direct. We used to have that quality. Some stations still do some of the time. Most should have their Optimods crushed.

STB

The big and brash days of ignoring deviations levels may be gone but perceived loudness within licensed parameters is still on from what I hear, especially when I am in Dublin. Nova vs Spin vs 104 vs 98 vs Today.

Processing is necessary given the different sound sources and levels a mixer would generate. Even Mic sources have their own processing prior to the joining the audio chain (the jocks in some stations even have their own settings!) What you are saying is that they should all sound flat ?

The Sound Engineer wasn't a dig at you. Me Kevin Street, Comms Eng btw. Anyone who has ever worked in radio will tell you that every DJ thinks they are an engineer, this goes back to the very start of commercial use of FM in Ireland.

There was a beautiful FM processing vanity discussion on RW between Frank Foti and Bob Orban years ago that you would have loved.

Codecs used in audio streams for DTT/DAB and Processing used on FM are seperate issues.

watty wrote: »

Most should have their Optimods crushed.

No way, prized possessions! Everyone should have an 8100A in their collection.

jeckle

Slightly off topic, but my Saorview radio channels are coming through in stereo apart from RTE Radio 1 & RTE Radio 1 Extra, which are coming through in mono. Is this normal?

Johnboy1951

jeckle wrote: »

Slightly off topic, but my Saorview radio channels are coming through in stereo apart from RTE Radio 1 & RTE Radio 1 Extra, which are coming through in mono. Is this normal?

Just checked here ...... both RTE 1 and 1 Extra are transmitting the same content ..... Ronan Collins show.

Both are in Mono ....... details of RTE1 ....

Stream 5
Type: Audio
Original ID: 1226
Codec: MPEG Audio layer 1/2/3 (mpga)
Language: English
Channels: Mono
Sample Rate: 48000 Hz
Bitrate: 96 kb/s

EDIT: I note that 'Choice' is also at 96 kb/s but is in stereo ..... all others appear to be 128 kb/s stereo ..

watty

STB wrote: »

What you are saying is that they should all sound flat ?

The Studio Processing or Radio Transmission in no way should interfere with the dynamic range or frequency response, except to limit it to the Modulation/Spectrum parameters.

Pre-recorded material should sound like it does it played direct. To change it is vandalism and arrogance.

There can be some flexibility for difficult voices (Should they have a job as a Presenter/DJ?) and Live performance. But only as a good studio would do making an Audio Book.

I've noticed and increasing tendency for the "Impact" and "Sound" to be more important to TV, Film and radio than the clarity of dialogue / voice or fidelity to original. It's arrogant stupidity that we now have poorer quality than 1960s FM and in some cases even than 1930s & 1940s AM Radio.

My oldest AM Radio is a 1945 Portadyne with wooden cabinet and 6" speaker. It's a 1936/1937 design AC/DC set. BBC R4 on LW sounds better than RTE1! R. Scotland and R. Wales better than most of the other MW at night. Some UK stations sound like a drain pipe feed into a giant oil drum. Ghastly. It of course sounds superb fed via RF signal Generator with an Induction loop and external AM in from my PC instead of 400Hz test tone.

I have 1955 (Ekco), 1958 (Siemens), 1960 (SABA) and 1962 (AEG) valve sets with VHF. Again and RTE1 & 2FM, Local Radio sound poor to Ghastly. The Mid West Hospital Radio sounds better than most! Best quality is MP3s via itrip. Next best is maybe Lyric FM. (I've had a tour in there as it's in Limerick). Satellite stations vary from good to terrible (Motorised Dish and Satbox feeding HiFi direct in Workshop and also the €6 "iTrip" like gadget, also PC with 2 x Sat cards and Dual DTT tuner on 4 satellite feed Multiswitch). ALL the Saorview Radio channels sound poor (direct on HiFi From PC based Sat/DTT Tuner), crap bitrates in many cases for MP2.

BBC Radio used to be all 256K MP2 on Satellite. Now R4 is 192K and R.Scotland is now only 128K, which is too low for Stereo MP2. The evenings that AM signal isn't fading or having co-channel interference (Spain/Portugal?) the R. Scotland on AM sounds less distorted!

The LG BD player/Home Theatre Amp has an FM tuner. Again it's limited by fact that most of the FM Radio stations are Transmitting for people driving a Lada with a broken exhaust and missing window. It's a bad showing when a €6 CE marked Hong Kong no-name "iTrip" on a PC playing 256K VBR MP3s ripped from your own CDs beats most radio stations for transmission quality.

watty

Johnboy1951 wrote: »

details of RTE1 ....
MPEG Audio layer 1/2/3 (mpga)
Channels: Mono
Sample Rate: 48000 Hz
Bitrate: 96 kb/s

EDIT: I note that 'Choice' is also at 96 kb/s but is in stereo ..... all others appear to be 128 kb/s stereo ..

At 96kbps Mono they would get better quality with limiting input with 9KHz or 10KHz filter and sampling at 22kHz!

96Kbps I presume must be "joint stereo" rather than 2 channels. Stupidly low bit rates for 48KHz sampling, never mind even Joint Stereo. No wonder it sounds like a radio with a near flat battery. They would be better having Choice in Mono at 22kHz sampling (appropriately filtered).

Johnboy1951

An interesting discussion developed here for those with some interest ...

http://www.richardfarrar.com/what-is-joint-stereo/

watty

That's a reasonable simplified explanation of Joint Stereo. The Difference between JS and FM Stereo Multiplex is that JS could use different encoder settings for Sum and Difference (like Colour TV uses massively more information for the Black & White image and much less for chrominance). In FM the L-R signal needs better reception than the L+R mono. If the signal is good enough, then the L-R and L+R are equal quality. As the signal is poorer the "L-R" 38KHz signal gets noisy first. Simple Stereo decoders simply switch to mono and ignore the L-R signal if it's too poor. More expensive decoders (I've seen one from 1965 using valves) use a variable matrix gradually decreasing the amount of 38KHz "L-R" toward mono as the quality decreases.

With MP2 encoded Digital you can't do this. You either decode all the signal or not. There is a narrow band of reception level where the signal is still decoded but not properly or consistently (Bubbling mud and drop outs to silence). DAB needs very much better transmission coverage for Mobile and Portable than was first realised because it doesn't have the graceful degradation to Mono and then gradual increase of noise as the signal is worse. This means full DAB coverage in UK is going to be maybe x4 expensive than was originally thought. But no-one really knows.

Also inherently rapid channel changes are more difficult with DAB than FM.

Fuzzy Clam

watty wrote: »

The Studio Processing or Radio Transmission in no way should interfere with the dynamic range or frequency response, except to limit it to the Modulation/Spectrum parameters.

Pre-recorded material should sound like it does it played direct. To change it is vandalism and arrogance.

There can be some flexibility for difficult voices (Should they have a job as a Presenter/DJ?) and Live performance. But only as a good studio would do making an Audio Book.

I've noticed and increasing tendency for the "Impact" and "Sound" to be more important to TV, Film and radio than the clarity of dialogue / voice or fidelity to original. It's arrogant stupidity that we now have poorer quality than 1960s FM and in some cases even than 1930s & 1940s AM Radio.

My oldest AM Radio is a 1945 Portadyne with wooden cabinet and 6" speaker. It's a 1936/1937 design AC/DC set. BBC R4 on LW sounds better than RTE1! R. Scotland and R. Wales better than most of the other MW at night. Some UK stations sound like a drain pipe feed into a giant oil drum. Ghastly. It of course sounds superb fed via RF signal Generator with an Induction loop and external AM in from my PC instead of 400Hz test tone.

I have 1955 (Ekco), 1958 (Siemens), 1960 (SABA) and 1962 (AEG) valve sets with VHF. Again and RTE1 & 2FM, Local Radio sound poor to Ghastly. The Mid West Hospital Radio sounds better than most! Best quality is MP3s via itrip. Next best is maybe Lyric FM. (I've had a tour in there as it's in Limerick). Satellite stations vary from good to terrible (Motorised Dish and Satbox feeding HiFi direct in Workshop and also the €6 "iTrip" like gadget, also PC with 2 x Sat cards and Dual DTT tuner on 4 satellite feed Multiswitch). ALL the Saorview Radio channels sound poor (direct on HiFi From PC based Sat/DTT Tuner), crap bitrates in many cases for MP2.

BBC Radio used to be all 256K MP2 on Satellite. Now R4 is 192K and R.Scotland is now only 128K, which is too low for Stereo MP2. The evenings that AM signal isn't fading or having co-channel interference (Spain/Portugal?) the R. Scotland on AM sounds less distorted!

The LG BD player/Home Theatre Amp has an FM tuner. Again it's limited by fact that most of the FM Radio stations are Transmitting for people driving a Lada with a broken exhaust and missing window. It's a bad showing when a €6 CE marked Hong Kong no-name "iTrip" on a PC playing 256K VBR MP3s ripped from your own CDs beats most radio stations for transmission quality.

The point is that stations are aiming at those on the move and listening on office radios. Not the purist at home with their B+O system. Unprocessed audio just doesn't cut it in the competitive radio market and it's daft to assume that they should broadcast as you suggest just to appease a minority.
If you want the highest quality, then buy the CD (or even better, vinyl ).

When 4FM 1st came on air , their stream was unprocessed and IMO was unlistenable to. The difference in levels between news readers and other programming was unbelievable.
TV3 had no processing for a couple of days several years ago and likewise was difficult to listen to with all the varying levels.

Sure, maybe there is a place for a station with no compression, say Lyric for example, but not mainstream radio.

Having said all that, I totally agree with much of what you have said. 5 band processing does destroy the EQ balance. And the harshness you have mentioned is probably down to increased clipping to increase loudness. I

To suggest that we do away with processing is ridiculous but a compromise is possible . 2 band processing gives the best trueness of source to output audio without affecting the EQ too much. But there's no chance of us going back to that.

bob11

Slightly off topic, but has anyone else notices that RTE 2FM has gone msising off Saorview ?


I normally listen to 2fm through my tele, but It has disappeared this morning ..
I'll have to make do with Pat Kenny on RTE Radio One ..

Johnboy1951

bob11 wrote: »

Slightly off topic, but has anyone else notices that RTE 2FM has gone msising off Saorview ?


I normally listen to 2fm through my tele, but It has disappeared this morning ..
I'll have to make do with Pat Kenny on RTE Radio One ..

Colm Hayes is coming in OK here .... did not check it earlier.

bob11

Johnboy1951 wrote: »

Colm Hayes is coming in OK here .... did not check it earlier.

Back on now again ..

It was definitely off for a an hour or 2 this morning ..