DAB Radio Streams

[zamarky1]

Hi All
not sure if this is the right area to post this question, looked around and could't see anything obvious as to where it might belong better so........

Does anyone know the lowdown on DAB radio ? I want to record DAB streams to HD then burn to cd both PCM and MP3.

I do know the minimum quality requirement for transmission here in U.K is 128kbps. I saw somewhere a few stations are transmitting at 192Kbps. My main concern is the format this would be transmitted in. Ie what sort of compression scheme would it be? not mp3 i am sure. So if it is in some proprietry schem what are the implications for converting to PCM tracks ? and what about MP3 given that the stream is already compressed. I am thinking quality issues recording from whatever format it is in to MP3 (ie transcoding). Which programs would best handle it and does anyone know the best way to cut up the stream into indivual tracks ? maybe there is a proggie designed just for this ......

Would FM radio give a better result ? (regards quality issues with DAB being transcoded from one digital format to another when recording and burning) some say FM gives a better sound then DAB ?


Thanks for any replies that may be forthcoming

I love this forum having found it just a few days ago, now i live here:-)

mark

[Imperial Llama]

I do know the minimum quality requirement for transmission here in U.K is 128kbps.

This is only for stereo music; speech and mono music are allowed to use a lower bitrate. There is one news station where I live that is broadcast at 48kbps mono.

I saw somewhere a few stations are transmitting at 192Kbps.

BBC Radio 3 is the only station to use 192kbps and it drops to 160 kbps when 5Live Sport Extra is being broadcast. Classic FM and Virgin Radio also use 160kbps. Everything else is 128kbps or less (there maybe some local stations in other regions that still use more than 128kbps but I don't think there are many).

My main concern is the format this would be transmitted in. Ie what sort of compression scheme would it be? not mp3 i am sure. So if it is in some proprietry schem what are the implications for converting to PCM tracks ? and what about MP3 given that the stream is already compressed. I am thinking quality issues recording from whatever format it is in to MP3 (ie transcoding).

It uses MPEG-1 Layer 2 (a.k.a. mp2) which is the same audio format used in VCD, SVCD, .mpg video clips and many digital TV platforms and there are plenty of tools available to convert it to PCM or MP3.

Some mp3 players, and cd/dvd players that playback mp3 CDs, can also play back mp2 files. I believe (although I'm not 100% sure) that the mp3 specs are written in a way which would mean that a standard compliant mp3 decoder would be able to decode mp2 too, although in practice this doesn't seem to be true for all hardware players. Some hardware players work fine with mp2 files, others will work as long as the extension is .mp3 ;), but some don't work at all.

Because nearly every computer that can play back mpg movies or mp3 files can also playback mp2 files with out installing additional software I never bother converting them to mp3.

Which programs would best handle it and does anyone know the best way to cut up the stream into indivual tracks ? maybe there is a proggie designed just for this ......

I use mp3DirectCut to cut the mp2 streams I record. BeSplit can also be used for this. For converting to PCM I use BeSweet so I can normalise and downsample it to 44.1 kHz for CD burning. If I needed to convert to MP3 I'd used BeSweet for that too.

Would FM radio give a better result ? (regards quality issues with DAB being transcoded from one digital format to another when recording and burning) some say FM gives a better sound then DAB ?

This will depend on the quality of your FM reception and personal taste. Many digital stations use different audio processing and dynamic range compression from their analogue versions which makes them sound different so you may end up preferring the DAB version even though you can easily notice the encoding artefacts at 128kbps. Different radio stations sounds better than others, and the different music styles sound better at low bitrates than other too.

If you PM me with a list of radio stations and music styles you listen to I can record you some samples for to check out yourself. Due to my webspace limitations it won't be more than 20MB of clips so choose wisely. ;)

If you are only interested in BBC stations you may wish to consider recording your radio from Freeview instead of DAB as the bitares used are higher. I think Radio 1-4 are at 192kbps, 1Xtra and 6Music are at 160kbps, and BBC 7 is at 128kbps stereo (compared to 80kbps mono on DAB).

Hope this helps clears a few things up for you. :)

[zamarky1]

Hi ya Imperial Lama ya all right ?

(just practising my british accent - if you live in U.K you'll know what i mean)

Thanks very much for your input. Excellant reply. Spells it all out PERFECTLY. A really good part to your reply is you just saved me 1oo quid :-) . You see i was going to buy a DAB PCI card AND a Nebula TV card to record TV programming as well, but seeing how the bitrates for audio broadcasts are higher on Free serve Vs DAB then i would be much better off to record from there (free serve) and be able to get the TV programs i want as well. So instead of buying two cards i only need one :-) BRILLIANT. The downside is i dont have anywhere near the choice of music to grab from FREESERVE but i'd rather not have it if i cant grab HIGH quality. Another aspect is disk space trying to record everything out there, so its not so bad being a bit limited. The last Aspect is when i go back to the bush there is no DAB so its a waste of a card ie i cant use it out there (same for Nebula card but at least now i will be trashing one card not two ) GREAT GREAT GREAT THANX !!!!

Man i tell you i LOVE my new home ...Doom 9

Best Regards

Mark

[zamarky1]

Hi Ya

Mr Llama
just wondering if you could tell me where you find the info on bitrates for the varius stations transmitting on both DAB and Free serve. I have spent quite a while digging around and cant find the info anywhere. Is there a site maybe that has this info on it?. Failing that i am planning on phoning the stations to find out more but thought maybe you have a source for this info?

One other thing. How is FM stero transmitteed ie what format and if this is ripped to a wav how would that quality be ? I mean its not digital per se so i guess you cant associate a bitrate with it , so how do you come up with a quality reference for FM?

as always any reply most appreciated.

Regards
Mark

[Mug Funky]

FM quality depends on your reception...

usually it comes lowpassed at about 15khz.. so you could get away with 128mp3 with it (could even go lower). i've seen the bandwidth as high as 18khz before though.

the stereo signal of FM is (i think) mid-side coded, so the limited bandwidth can be used more efficiently (that's why you always get a better signal in "FM mono").

concievably you could encode in all-mid-side mp3 (-m f in LAME) but this mode breaks easily when more spatial sounds come.

[Imperial Llama]

@zamarky1

There is some information on DAB and Freeview bitrates here:

http://www.wohnort.demon.co.uk/DAB/
http://www.digitalradiotech.co.uk/

The forums as Digital Spy also good resource for information about UK digital TV and radio:

http://www.digitalspy.co.uk/

[zamarky1]

hi Ya

@Imperial Llayma

Thanx will check it out


mark