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What sort of mp3 output quality would a radio station be? (Please)

My car stereo chews up the cd's - pretty much because the shock absorbers are rubbish.
Way to go, Chevrolet...

So I got a car fm transmitter that plays mp3s - and it's great stuff. Yay!
(and cheaper than new shocks, too!)

However, I want to cram as many mp3s on the player as I can (it's only 4gb)
so I'm going to convert my mp3s to a lower quality. I guess as I'm happy with
 records on the car radio then I reckon I don't really need cd-quality mp3s.
(I can listen to hi-fi at home ;-)

I did a quick Google, but found no answer to my question - what sort of mp3 output
quality would a radio station be? I'm happy to reduce the frequency sampling as well
as the bit-rate.

Many thanks guys.

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Jayefuu6 years ago
To answer your question:

"Commercial FM radio stations use 384 kbps or 256 kbps" - Source.

Load your typically listened to song at 128kbs and 256kbs onto your mp3 player. Drive along a road at your max legal speed (when your car's noisiest). Play both, can you tell the difference? If not, go with 128kbps.

If it were me I'd invest in a car stereo with an auxilary input or a flash card slot. Then you can plug your mp3 player or memory card directly into the stereo. No faffing with fm transmitter leads or turning on separate things when you start your stereo.


orksecurity6 years ago
Frankly, given the noise level in the car, even a low-quality recording can sound pretty darned reasonable -- you really aren't going to hear anything but the strongest frequencies.

I have a few cassette tapes (from rehearsals) which are so noisy and off-balance and (in spots) off-key that they're unlistenable at home -- but in the car they sound just fine. Apparently when I can't hear it well I interpolate past errors that I normally couldn't ignore. Let's hear it for psychoacoustics.
Also: Many non-classical commercial radio stations, because they know you'll be listening in noisy environments such as cars, and because levels differ from one recording to another and require adjustment to keep you from having to tweak the volume with every song, put the audio through a compressor (fancy automatic gain control) before broadcasting it. That effectively cuts out a significant amount of bandwidth, by destroying the music's dynamic range. (Note that the RIGHT answer would be to broadcast with full dynamic range and have the folks listening in noisy environments run a compressor of their own -- but that ain't gonna happen.)

When doing local playback, you're going to have to decide whether to compress, and whether you can compress at playback (probably not, though most modern media players *could* do it if the firmware authors wanted to make the effort) or at the time you set up the digital files (more common, but means that you need to keep two copies of the file if you want both compressed and genuine high-quality copies).

kevinhannan (author) 6 years ago
thanks, Jayefuu.

I'd go with the idea of getting a new car stereo with such a slot. The only trouble being is that the local scallies (hoods) would like it more than me... ;-)

I've done what you've suggested and gone right down to mono from stereo, to 22kHz from 48kHz and from 128kbps to 64kps and guess what? No-one I've asked can actually tell the difference! Now either they are deaf or my car is noisy - take your pick! The bonus is 25mp3 tracks was 130Mb is now 34Mb - what a saving!

Many thanks for the pointer. ;-)
Damn those scallies. Keep an ugly cheap stereo in the dash but hide the good one under the seat? :D
kevinhannan (author)  Jayefuu6 years ago
lol! my wife strip searches my pockets each time I leave home - no chance for a decent stereo! But thanks for the commiserations!
You've got to compare the actual FM channel quality, as much as the MP3 bit rate I reckon. Good, wideband FM (Radio 3) is about the best it gets, and has an SNR of only about 65 dB.